Transcript for:
Organic Chemistry Overview

[Music] [Music] hello my name is Chris Harris and I'm from Mallory chemistry and welcome to this video on Edexcel topic 18 organic chemistry 3 so this video is specifically designed for I'm at excel chemistry so if you are studying at excel a level chemistry then this video is perfect for you so sometimes you can look at some resources online and you can you wondering if it's in the specification is this relevant to me and well while this video is okay it has everything that's dedicated to it MIT there's actually linked with the specification as well from format excel so this is perfect for you and in fact there is a full range of Edexcel videos from year 1 to year 2 that covers the full range of information that you do need to know for at excel as well as whiteboard tutorials as well and exam work through so quite a comprehensive set of resources there and it's all free all he asked you to do is just hit the subscribe button and that would be fantastic so so if you do that that'd be brilliant and as long as people keep subscribing and keep watching the videos then I will keep making them and keep adding to it as well so um if you want your own copy of these resources here and then they are available to purchase if you just click on the link in the description box there very good value for money and it means you can use them and your smartphone or in your tablets and you can use them whenever you want you know whenever you want to use them we can even print off the slides and use it as part of your revision notes so so there is so there is plenty of scope there so you can access them there as well I like to say it is important to do exam practice as well so it's one thing knowing the content it's another thing actually doing it so so we're going to go through everything we need to know for topic 18 now this has probably got to be one of the biggest topics for Edexcel so bear with me but this one but it does contain everything that you need to know for topic 18 so it is it is condensed into into that topic but you can obviously skip to the bits which which you which you want to you know which you which you want to know about you know once you get you familiar with this video okay so like I say it is dedicated to the specification and this is the third organic chemistry topics there's quite a big area of chemistry as you can see so we're going to look through a Wiens and which is benzene molecules and then we're gonna look at a means and a mines amino acids and proteins so we're going to look at that that area as well as well as we're going to look at some organic synthesis later on so that means we're going to be looking at synthetic roots and see if you can know if you can remember the reaction conditions are gonna have a little bit of a little bit of a quiz later on regarding that and then obviously we're going to look at practical techniques as well towards the end of the video okay so let's start with benzene so benzene is a cyclic planer molecule with a formula c6h6 it has four Cove has four valence electrons and each carbon is bonded to two other carbons with one hydrogen atom and the final lone electron is AP orbital which sticks out above and below the plane of ring so you can see it there so you see we've got a carbon atoms there are P orbitals are above and below this atom and got hydrogen's that stick around on the outside so the lone electrons in the P ops or what they do is they combine to form the delocalized ring of electrons and you can see it there it looks like a bagel or a doughnut or something so you've got the electrons here these then start and fold towards each other and form as delocalized structure here which is quite unique and actually due to this delocalized electron structure all of the CC bonds and the molecule are actually the same length they have the same bond length of 139 picometers so that's quite unusual and so benzene as you can imagine will have some quite unique properties when it comes to reactions and and looking at its physical physical properties as well so the carbon-carbon bond length in benzene lies somewhere between 154 picometers which is the bond length for a single bond and 134 pick picometers for a double bond so this does suggest that actually it isn't straightforward and of just single and double bonds as we're going to look at the the proving of the structure of benzene because it's it's not quite as straightforward as you as you might think so benzene is normally drawn in a skeletal formula okay so it makes it a lot easier to draw rather than draw on all the carbons and hydrogen's and all the bonds in the hexagon so we show the structure benzene and the skeletal form like that now the structure there is actually showing all the double bonds that are in benzene and this is called the calculated structure and this was named after a scientist called August kekulé a who basically discovered it and he thought that actually there was alternating double and single bonds and so you might see it drawn like this but most often and actually what you should be drawn as is the is the other way and which is this way as it comes up there we are okay so it comes up with the circle in the middle and that just symbolizes a delocalized set of electrons so you can see here we've got a delocalized electron ring and we can say that both can be used both the technically right normally the the calculation structure is used when we're trying to describe like reaction reaction mechanisms except for some chemists prefer to use that and but you will see it more common as the one with the circle in on the right there so remember because this is a skeletal formula it doesn't show the carbons or hydrogens but there are hydrogens attached to each carbon so don't forget that so especially this is going to be more important to not forget that when we look at reaction mechanisms such as friedel-crafts reactions nitration etc so that's going to become more important but you'll get used to it okay so benzene is actually more stable than theoretical than the theoretical alternative cyclohexane one three five train so that's calculate structure so that's the alternating single and double bonds so and this actually proves the delocalized system so actually if we measure the stability of benzene by comparing the enthalpy change of hydrogenation in benzene and in cyclohexyl one three five train we can actually you know prove that actually benzene does have this delocalized system so for example if we hydrogen its cyclohexene so it has an enthalpy change so this is the adding hydrogen on to the double bond and it has an enthalpy change of a - 120 kilojoules per mole so that's the enthalpy change for adding hydrogen to one bond and you can see on there that the the reaction effectively that takes place so in theory it should be minus 120 kilojoules per mole so you think because we have three double bonds in benzene then that would just be three times minus 120 so that means the energy would be minus 360 kilojoules per mole that's what you would think isn't it however when we measure the enthalpy change of hydrogenation for benzene it's a lot lower it actually comes out at minus 208 208 kilojoules per mole now this is doubly the experimental value this is you know the value that we get and we actually do this have this reaction so you can see the predicted one would have been minus 360 kilojoules per mole but actually benzene comes out at minus 208 so what does that mean well it means like the energy required to break the bonds and the energy released to form the bonds so this just that actually more energies required to break the bonds in benzene and done it is in cyclo hexa 135 trying okay so this basically tells us remember bond breaking is endothermic so you need energy to break them bond forming releases heat energy so this is actually coming out at lower it's less exothermic than we thought so what this means is that our g benzene is more stable than the theoretical cyclo hexa 135 train and whether you've got the three separate double bonds and so the stability is mainly due to well it is primarily due to that delocalized electron structure in there it you know the reason why benzene arranged itself in that way with the delocalized electron structure is to increase its stability so it is a lot more stable doing it that way so it's very different so it's all exciting right thankfully look if you there's loads of stuff on this and hoods of reactions and everything um so we're going to look at the combustion of benzene why not it wouldn't be chemistry though burning something with it so so we look at the combustion of chemistry so benzene is a hydrocarbon and like many hydrocarbons it burns readily in oxygen okay and now benzene burns and oxygens produce your carbon dioxide and water if it's burnt completely if it isn't obviously produced source and carbon monoxide etc just like with any other hydrocarbon so the combustion reaction for benzene is to lots of c6h6 15:02 will form 12 co2 and 6 h2 us there's nothing different there so you will be expected to balance the equation but the products of combustion are the same if it's complete combustion as it is here it's carbon dioxide and water so in reality though and we don't live in a perfect world so in reality carbon doesn't burn completely and so there's never enough oxygen to burn these things completely in air and as a result we do get a lot of unreacted carbon atoms which has things like soot and actually benzene generally burns with a black smoky flame as you can see you know the diagram there is just showing what benzene could burn like so with back with a big smoky flame there because it's more likely to burn it's rare for any reaction to burn completely to have sufficient oxygen there it's it's incredibly oh you're always going to get some incomplete combustion and benzene you know has this evidence of this as well ok so what we're going to do is we're going to look at addition reactions ok so we're going to look at we're going to compare basically reactions where you would have you're adding a molecule to a double bond and then we're going to look at how benzene actually reacts because benzene doesn't really have double bonds it doesn't have single bonds either it's got this halfway house so all going to do is do a compare and contrast and talk about the types of reactions that you do get with benzene and there's a good bit of benzene chemistry is really to do with the reactions and mechanisms so we're going to start with first looking at a type of reaction is if we had a double bond and this is the addition of bromine to a double-bond and we call this electrophilic addition okay because alkenes with the double bond a bit like the calculate structure that we'd seen before and they undergo electrophilic addition so if we aren't bromine water to an alkene this causes a color change from browny orange to colorless so remember bromine is that Brown the orange color so this Brownlee orange color of bromine is bromine is actually the electrophile and this adds to the alkene form and dye bromo alkene which is colorless so remember an electrophile is an electron loving species so bromine is actually going to be attracted to the high electron density and the double bond as you're gonna see here so here we are we've got our alkene now what happens when bromine a bromine molecule BR 2 is normally neutral doesn't have a charge because you haven't got a you haven't got a charge difference here but as the bromine molecule approaches the alkene with loads of electrons we actually induce a dipole in bromine so what we get as you can see there used to be pointer here so you've got Delta negative bromine and the Delta positive bromine atom here because this end of the molecule is close to this which effectively nurtures the electrons to one side so it's like a temporary dipole now this polarization now makes it quite reactive so let's have a look so we've got the electron pair in the double bond like we say here that's attracted to the Delta positive bromine and this forms a bond with the bromine and starts to break this bond here or sever this bond so let's have a look here so we've got the electrons moving from the double bond to the Delta positive bromine remember curly arils always show the direction of electron transfer so this is moving from the double bond to the bromine and you can see that then breaks the bonds between the bromine and it forms our intermediate which is our carbo cation they can see here we've got the bromine that's added on there the double bond no longer exists now and we have a an electron deficient carbon there in the middle but member we still have our bromine over the bromine atom that's floating around now this has a negative charge because the electrons in the bond have moved on to us and as a lone pair of electrons so what do you think is going to happen here well no surprises the bromine is then going to attack that Delta positive carbon and then we finally we get our product which is colorless one to dye Bromell ethane is formed okay so this is an electrophilic addition reaction because we're adding to the double bond and we'll look at reaction types later in the video as well but we're adding to that double bond and because we're adding to that double bond and we're adding so we're adding using bromine bromine is your electrophile because it is attracted to the high density of electrons in the store bond hence the word electrophile okay so now just keep that in your mind okay the reactions of adding bromine to an alkene we're now going to contrast that with reactions of a Wiens okay so when a Wien is undergo when and Aliens undergo reactions they undergo electrophilic substitution reactions despite the fact that they've kind of got a bit of a double bond in there kind of like a halfway house between a single in a double bond so benzene has a high electron density and because of that delocalized arrange structure and this is attractive to electrophiles o cases electrophiles remember these electron love and species so that's fine because previously with normal double bonds we had electrophiles because they've got a high electron density so that's normal but and as we've seen benzene is really stable it's not like a normal alkene so unlike traditional alkenes they do not undergo an addition reaction so like what we've just seen before so this would disrupt that benzene ring and remember if you've seen any of the other videos then i always say that atoms and molecules incredibly lazy they don't want to be put in a position where they're high higher energy than they need to be so because of this nice stable benzene ring and to disrupt that benzene ring is just it's just not gonna happen easily so you need something with some clouds to really break that ring open and actually add your functional groups to that to the benzene ring so instead they undergo a substitution reaction so this is where remember one of them hydrogen's around the benzene ring is substituted for the electrophile that were reacting it with and so there are four mechanisms that you need to know I know it's a lot and there's four mechanisms don't worry they all they all follow the same mechanism so don't worry about that so just see it as four potential opportunities to gain marks the mechanisms are the same so Janee if you remember the mechanism you can apply it to any of these so that's fine so there's a friedel-crafts isolation friedel-crafts alkylation yes they did two reactions because they're greedy there's halogen halogenation reactions as well and nitration reactions so we're going to go through all four of these and we're going to look at the reactions of benzene how we add first of all what friedel-crafts reactions are and then looking at halogenation and nitration reactions and seeing how these mechanisms work right so aromatic compounds are molecules remember that contain a benzene ring so just just to go through this before we actually go into the actual reactions of these we need to understand what were actually how we name these okay so this is just a before we go into the reactions about the negative show of them so there are known as their a Wiens are known as automatic compounds so molecules that contain benzene rings are known as a Wiens and they're named in two ways and so what we do is we name some of them with benzene at the end such as bromo benzene you'll see that later in the reaction we're going to see things like methyl groups so one two dimethyl benzene so we'll put benzene on the end for that one and also things like nitro benzene so you're going to have a look at some of these reactions here it's just so you know how we name them but sometimes and we use the word Fe Nile for example so we'll look at phenols later as well but phenol is just a benzene ring with an alcohol group and hydroxyl group attached on the end and sometimes things like phenol amine is another example where actually we use the word female at the start there so you just need to be familiar you're not going to know you're not going to you don't need to know many reactions for this in in the scope of chemistry of course but so you do need to know that and when to use benzene at the end and which ones are going to use female but you'll get used to them because you'll see written and drawn so many times okay so as we've seen before benzene undergoes electrophilic substitution okay so remember that's what that's what mentioned there and we need to know specific reaction conditions associated with these types of reactions so for example here's our benzene ring and we've got an electrophile an electrophile this one here has a positive charge and that's that's an important point because remember it's no point in just having a delta positive so a weak kind of part partial positive charge and a molecule that just isn't going to cut it that isn't gonna break this benzene ring apart and so you can do a substitution what we need is a real proper positive charge on our molecules or highly reactive species so the electrophile and the delocalized electrons in the benzene ring these attack the carbo cation which is more than likely going to be unless is unless is halogenation or different or a nitration reaction but it's going to attack a delta positive carbon in this example here so the electrons move from the bond which breaks the ring and a positive charge starts to develop so you can see here the electrons in the CH bond that's that's been that exists here then move back into this disrupted benzene ring okay it's temporary and then what happens is the electrons jump in here and that reforms this benzene ring and effectively the hydrogen has been substituted so we've got our electrophile here with the positive charge and electrons jump onto here onto the electrophile and then that effectively adds itself on there so this is d so that should say e mainly for electrophile so that adds itself on there and then the hydrogen the electrons on this bond goes to the positive charge and then we're left with our electrophile is added on there so that should say e for these ones because i it's the the mechanism is the most important bit here but so it's the electrophile that's been added on so benzene rings are very stable molecule so reactions are difficult so we need a very strong electrophile to so thankfully we can wecan these can be created by using something called hari halogen carriers which is going to be vitally important for any any types of these reactions so you'll see how halogen carriers work later but typically housing carriers are aluminium based so they're aluminium here lights for example alcl3 so you need to know this is the generic reaction for electrophilic substitution reactions so we're going to look at specific examples obviously the the reactions that were mentioned before okay so remember one of the four that you need to know of the specific reactions were friedel-crafts reactions now benzene is used widely in the pharmaceuticals and dyestuffs and it's widely used in these industry in these types of industries so it is important that we need to know about these reactions and how we actually add things to the benzene ring and change it to make it suitable for what we want to use it for the stability though of benzene is difficult so what we need to do is these two people which is friedel-crafts i'll show you them in a minute they came up to with a solution to how do we actually react things with benzene so here they are here we've got Charles Friedel and James Kraft and they were French and American scientists and they came with the reaction where an acyl group or an alkyl group can be added onto a benzene molecule and so after the acyl alkyl group is added the benzene structure is weaker and it makes it easier to modify to modify it further to make the useful product so that was the idea was to initially just to add the molecule the group onto the benzene ring make it we care and then we can actually add whatever you want with it after that so in order to do this the benzene ring in order to add it to the benzene ring the electrophile must be powerful and so therefore it must have a positive charge a proper positive charge so acyl groups have a positive charge however it isn't positive so remember what I said last time where a delta positive won't cut it it has to be a full positive charge for these reactions to go and so we use the halogen carrier as a catalyst remember which is aluminium chloride alcl3 and this will actually allow us to produce that stronger electrophile first then what we do with that electrophile is then react it with the benzene ring so we have to make it first then use it okay so in the friedel-crafts isolation or alkylation we react an acyl chloride or halogen or alkyne with the halogen carrier to create that strongly positive electrophile okay so that's what we're going to look at now on the next slides we're going to be looking at how you actually make the powerful electrophile using this halogen carrier okay so to make it we need to go we need to undergo by this reaction here so aluminium chloride alcl3 accepts a pair of electrons away from the acyl group in this case we're going to do a solution for this one so you can see here that we've got an acid chloride here an acyl chloride and you will have seen that back in topic 17 when we looked at acyl chlorides in a lot more detail we react that with the halogen carrier which is alcl3 and as a result the polarization and a carbo-cation result of the polarization increases and the carbo cation is actually created here so we form a LCL form minus here and we form our carbo cation and this is what is then going to react with our with our benzene molecule so this is our electrophile okay so the strong electrophile because that was that proper positive charge okay so now we've made a positive electron that's how we've used it we now need to react it with benzene and we're going to make a less stable phenol ketone this is going to be done under reflux and a dry ether solvent so reflux is used when you want to you want to react to volatile substances together so if we heat these without the use of reflux then it would just evaporate into the atmosphere and work so we don't want that so we use reflux to effectively keep our reaction within within the reaction vessel it allows us to heat it to allow it to react but not allowing it to escape into the atmosphere so here's the first one so here's our carbocatine this is our electrophile and we've got our benzene ring so remember the general mechanism so the delocalized electrons they're attracted to that carbo cation the two electrons jump from the delocalized ring structure and a positive charge the jumps towards the positive charge in your electrophile so then what we have is this substance here so our our SR group is added onto the onto the benzene ring and you can see here that we've got a broken delocalized system and this has the positive charge there so the next thing with these is you can see that we've got our halogen carrier that's now obviously in this reaction at the same time so the next thing is the negative al CL 4 - so this halogen carriers then attracted to the positively charged ring and one of the chlorine atoms breaks away to form a new bond with the hydrogen so and the electrons from that bond then move into the positive the positive ring structure and this then effectively reforms the ring again and we've got our F in our ketone that's actually formed so you can see here that the halogen remember this was a catalyst your halogen carrier so because this has lost the chlorine we form alcl3 back again and the hydrogen and the chlorine from here formed hydrogen chloride gas and that's the critical thing is that the ring is reformed but we've broken that ring structure now and added that group on ok so we're going to look at alkylation as well and we have to make the a powerful electrophile again we're going to use aluminium chloride for friedel-crafts alkylation and so the mechanism we're going to show the mechanism below so this time we're going to use a halogen or alkane or halo alkane here so this already has a bit of priority on it already as you can see so the aluminium chloride accepts a pair of electrons away from the halogen you know alkane there we are okay and then them electrons there then reacts and jump onto the aluminium aluminium there and as a result we have a carbo cation that's formed which is left on the side there and then also we have a LCL for - that's thus remaining and we'll see how that reacts a little bit later on so the stronger electrophile is now produced there it is there this is it there's a strong electrophile and we're now going to use this to react with our benzene ring so let's add this to the benzene ring and again we do it into the same conditions reflux and a dry ether solvent so there's our alkyl group so again same system electrons from the delocalized system jump onto that alkyl group there okay and then we form this intermediate with the Delta positive charge this broken ring structure here but they are added on it's exactly the same as your the mechanism and then in comes our halogen carrier because it's attracted a halogen carrier is got a negative charge that's got a positive source attracted to it it's the same stuff okay so the electrons move to form a bond with the hydrogen so the chlorine is broken off as well off the aluminium of the halogen carrier and then the electrons move from that CH bonds to back into the ring to reform the ring structure again and then we've added our alkyl group here there it is there's an alkyl group that aluminium chloride catalyst has reformed and also we produce HCl gas as well so you see the mechanism is the same as it is for the friedel-crafts isolation reaction so it's no different okay so alcohol based groups can also be added to the benzene ring as well so we can see here there's our alcohol alcohol based group that attached that's touched on here we've got a carbo-cation so if we use an electrophile and that contains the an alkyl chain and with the o alcl3 so it's it's actually bonded onto the molecule here then this can add an alcohol based group to a benzene ring and it follows the same process so you can see here we've added this on accept our aluminium carrier our halogen carrier sorry is not actually separated has actually joined onto the so this molecule here this alcohol group this what would have been an alcohol group so you can see that the whole thing adds on on on here and we still have that positive charge in our benzene there and then what have done is of colour-coded it just so you can see what's going to happen here so the electrons jump from this bond here and they jump onto the oxygen and then the electrons from the oxygen move onto the hydrogen which is on there and then the electrons between the carbon and hydrogen move into that that delocalized electron system for stability so effectively what's happening here is this bond is breaking so that forms your alcl3 this is forming a bond with hydrogen to form your alcohol which is there okay so this is the alcohol based group so this works in a similar way to other friedel-crafts reactions as as the oxygen the group has a lone pair of electrons and this allows it to act as a nucleophile in terms of forming the bond with the hydrogen on there so it's a bit of a different reaction but it's a way in which we can add an alcohol based group onto a benzene ring but the mechanism is the same it's just this bit here which is a little bit different to all the other ones but nonetheless you still need to know how this reaction works okay so we're going to look at the nitration of benzene so that was the other reaction that we need to know so this is the third reactions remember had have had friedel-crafts isolation friedel-crafts alkylation and we've also got nitration of benzene so no traitor benzine is actually really useful because it allows us to make substances like dyes for clothing and explosives okay so such as trinitrotoluene which is tnt that's used for explosives so if we heat benzene with concentrated nitric acid and concentrated sulfuric acid and we form nitro benzene however like we've seen before we must create a really powerful electrophile first it's no good just using the Delta positive we need a full positive charge as an electrophile so the first step is to make the electrophile first and we do that we don't use any halogen carriers here so we're not doing that but what we are doing is we effectively react the nitric acid and sulfuric acid together first and you can see here concentrated nitric concentrate sulfuric that forms a ch2 L O 3 plus and hso4 minus ok so you can see that if you remember from your acid-base equilibria topic where we look at con conjugation and we look at the bronsted-lowry Theory about protons been received and accepted you'll see that we've got two acids here but the the nitric acid here is accepting a proton so nitric acid is actually acting as a base because it's accepting a proton to form this sulfuric acid is acting as an acid because it's donating a proton to form this so just be really careful that there was some strange because you think well hang on both of them are both of my acids but with yes they are both acids but they're behaving ones behaving as a base and ones behaving an acid that's why we've got to be very careful so the hno3 that we formed in that reaction then decomposes to form the electrophile which is the nitronium ion so we've got h2 n o 3 plus forms no.2 plus and water so now we use the nitronium ion which is no.2 plus and we react it with benzene to produce nitro benzene okay so that's the critical thing here so if you have a look we've got our benzene ring and we have no.2 plus we've got our nitronium ion at the top there so the reactions as you'll see are very very similar the mechanisms so the nitronium ion has that positive charge that's the electrophile and this is attached by the benzene ring formed an unstable positively charged ring as you can see on the bottom here so there's it positively charged ring we've added our nitrate group on there and we've got our hydrogen so then just like with the other ones the electrons in that hydrogen carbon hydrogen bond move in to reform that delocalized electron ring and then we get nitro benzene is formed and the H+ is formed which actually reacts with a hso4 - that we used in the previous one so remember one of the products of the previous reaction was hso4 minus the H+ that comes from the benzene reacts with that and that reforms h2 so4 so your h2 so4 is a catalyst okay so that's that's proof that that actually behaves the catalyst because it is reformed again it's not actually used up in the reaction okay so we've got to do this at temperatures at specific temperatures so at a temperature below 55 degrees this will ensure a single no.2 substitution so anything above this and actually what we get is multiple substitutions so we get substitutions that are attached onto multiple parts of the benzene ring so you've got to be careful with that because if you just want a mono substituted nitration reaction then you've got to do it below 55 degrees so normally you would do that in a in an ice bath you would put your beaker in the ice bath and let it's make sure it never goes above 55 because this reaction actually generates quite a lot of heat so it generates quite a lot of heat so we need to make sure it doesn't go above 55 I don't know if you've tried doing it you might have done nitration reactions already but if you have then you're no Oishi it's a very it heats up quite quickly okay so we're moving on to a different part which is phenol so phenols phenols have a hydroxyl group which is an OHA minus group and that's attached to the benzene ring remember we'd seen that before when we're looking at the nomenclature of some of these aromatic compounds are these a beans so phenols has that OAH group so there's your phenol there okay very straightforward but we can also have things like two methyl phenyl as well so your phenyl group has your Oh H group on the benzene ring on the top of the benzene ring and you can see that we're here we have a methyl group just coming off it so this is coming off the second carbon because we always say that wherever the O H group is that is carbon one and then the methyl group isn't carbon number two so this is two methyl phenyl okay here's another example this is salicylic acid so here we've got phenol and we have our carboxyl group let's hang it off on the end here so we also know this is salicylic acids you might have seen that but you'll see how that actually works when you make em aspirin so this is why it's going to be quite important for for this video okay so phenols are more reactive than benzene because mainly due to the higher electron density in the ring and this is actually directly caused by the Oh H group attached to it so electrophilic substitution reactions are much more likely to happen with phenol and than with benzene because of this orbital overlap that we have between the Oh H group and the and the benzene ring so you can see here the electrons and the p orbital of the oxygen in the O H group these are the ones that are in green in the diagram these overlap with the delocalized ring structure and so they are partially delocalized into the into the PI system so the electron density increases within that ring structure and so this means it is much more susceptible to attack from electrophile so you can see here these electrons here are moving in and are merging into this benzene ring structure which makes it even more electron rich then than what you would get with benzene okay so we're going to look at how you make aspirin aspirins quite a quite quite an important drug is probably a very old drug but aspirin is used as a as a painkiller and it's actually made by reacting ethanoic anhydride or ethanol chloride with salicylic acid and we'd see in salicylic acid as a obviously there's a phenol with your carboxyl group hanging off the second carbon so we're gonna see how that particular molecule can be used to form a pharmaceutical product such as aspirin so you can see there's our ethanoic anhydride so run hydrides have this this structure here where we have it looks like a carboxylic acid if you just look at that bit there the one in blue it looks like a car axilla acid and what we've done is we bonded another carboxylic acid to it so this is called ethanoic anhydride and I've color-coded it so you can actually see and where the atoms are being attributed to so this is going to react with are salicylic acid which you can see on there and this is going to form aspirin so this is the molecule for aspirin and we're also going to form our ethanoic acid so this is our carboxylic acid that's that's been formed here so that is the formula for aspirin so you need to know that reactions you need to be able to use a phenol based reaction here now just showing you where these molecules come from you can see the bit from the anhydride here adds onto the oxygen from the phenol so the hydrogen is removed which is this bit here and this hydrogen is then used to react with the remaining bit of your anhydride to form your ethanoic acid here which is also known as vinegar okay so ethanoic anhydride is used instead of ethanol core instead of ethanol chloride in industry and mainly because it's safer and less corrosive it's nowhere near as nowhere near as reactive and it doesn't produce harmful HCl gas you'll remember you'll remember from topic 17 when we looked at acid chlorides acid chlorides when they react with say alcohols for example and they which is affected what's happening here they produce HCl gas which is not very pleasant at all it's acidic and it's toxic so if we can come up with them a reaction where we're not going to produce products like that then that's got to be better and it's a lot cheaper to use which is from an economic side that's obviously quite good and it's a lot safer it doesn't react as vigorously as a cycloid so it's a much slower reaction a much more controlled reaction and again that's got to be better than using acid chlorides okay so phenols they partially dissociate which means they're actually weak acids okay so they fit into that category so they would react in the same way as any other weak acid would do such as a carboxylic acid so phenols dissociate weakly to form a phenoxide ion and H+ ion so your phenoxide ion is obviously this molecule here lost the proton member an acid a bronsted-lowry acid is a proton donor so you can see this is obviously donated the proton from there and phenols also react with alkalis to streetbet with any other acid and they form salt and water so in this case we're reacting it with sodium hydroxide and this is going to form the salts of sodium peroxide and water so this is again this is no different to a standard acid-base reaction it may look different applying it something else but it's not it's not something extra that you need to remember it's just something that if you know that acids react with bases to form salt and water we're just using a different asset that's all it just has a big hexagon attached to it okay so phenols they can react with bromine water and which is which is nice so phenols react with bromine water as phenols are more reactive than benzene so that the reacts a little bit more readily and we observe a brown D coloration so the brown color of bromine decolorizing as we form our products with the benzene with the bromine substituted in it so for example you can see you've got the phenol reacting it with bromine which is B R to the O H is what we call an electron donating group so remember it pushes it pushes electrons into the benzene ring so push it into there and so therefore what we actually get substitution occurring at carbons two four and six so the product is there for two four six tribe bromophenol so we get it one two and three because the alcohol is pushing electrons in there and we got that delocalized system so we get substitution at these points on the bromine on their benzene molecule okay so try two four six try bromophenol smells of antiseptic it's insoluble in water so it's quite oily you might have heard of another type of chemical which is quite similar which is called TCP that's called tri chloral phenol so you use chlorine instead of bromine so TCP is something you buy it in the shops and TCP is normally you would gargle TCP if you had and if you had a sore throat you would gargle TCP because it's a good disinfectant so and if you ever wondered what it smells like get yourself a bottle of TCP and get it in most places like boots and Superdrug or somewhere like that so you can get maybe the supermarket you can pick up bot the TCP and you can see what it smells like you might have some in the cupboard as well so and very antiseptic it's got that like kind of antiseptic smell so that's that's as close as you're probably going to get Sophie knows then react with dilute nitric acid so you can see that phenols react with nitric acid as well as benzene so remember with benzene we had to actually react it with concentrated sulfuric acid and it had to be concentrated nitric and we had to create but nitronium ion to then add on to the benzene so you remember that from there but with phenol and the O H is an electron donating group into this so that's why substitution occurs at carbon two and four in this case so all we do is we add our dilute nitric acid is enough we don't need to actually create a positive electrophile here and it just adds on to this carbon here carbon two and then carbon four here okay so we'll get two isomers produced with this types you've got carbon to nitrogen all and for nitro phenol here I was you might think my why don't you have one here as well well if we did have one there that would still be called to night or phenyl because that would be the second carbon so that's why we only get two there two isomers that are produced which is two nitrile phenol and four nitrile phenol okay and then they only occur in them spaces as well because it's an electron donating group as we've seen before okay so let's look at another area of organic chemistry which is a means so an amine is derived from ammonia molecules and it will contain a nitrogen atom and this is where hydrogen's are replaced with an organic group such as an alkyl group so we get different types of a means we get primary we get secondary we get tertiary and we get quaternary should we get a right family here so this is very similar to for example alcohols where you get primary secondary and tertiary alcohols and also halogen or alkanes when we looked at someone an sn2 reactions you get primary secondary and tertiary so this is the same except this is obviously looking at a means instead okay so let's have a look at the first one this is a primary amine it is this is the methyl amine so you can see here that we've got a nitrogen here and this only has one methyl group attached to it so remember this is what we're talking about so this is a primary amine secondary amines this has two methyl groups or two organic groups attached to it so we've got one here and one here so this is a secondary amine a tertiary amine is something like this where we have three methyl groups surrounding the nitrogen atom but that can be any organic groups enough to be methyl and then finally we've got quaternary salts and this is where we have four alkyl groups organic groups surrounding it over here but you can see that remember nitrogen can only bond three times this one's got four bonds so that means we have this positive charge and the nitrogen so it is a it is a salt and we can also get aromatic ones as well so this is phenol amine as an example so this is an aromatic amine it is a primary amine still because we only have one organic organic group attached to the nitrogen okay so these are non aromatic amines are known as aliphatic amines and you might see the word aliphatic used later on so whenever phone something has been aliphatic it means it doesn't have a benzene ring and basically okay so aliphatic amines are made in two ways okay so that either made by reacting a halogen or alkane with excess ammonia or they can be made by reducing a nitrile so what we're going to look at here is going to look at the first wave making it which is reacting a halogen or arcane and excess ammonia okay so with each step what we're going to do is we're going to add a halogen arakan you'll see this later on when we do the reaction so just keep that up there so you can see that and the mechanism for making each a mean is similar so instead of using two ammonia molecules we use to a means instead so here what happens is the primary amine methyl amine reacts with the chloro ethane to form a secondary amine so you can see here that actually here's our primary amine here and we're going to react us with halo alkane and that's going to add and form the primary amine and then the primary amines then going to react again with more halo alkane to form a secondary amine and that's going to keep on going until we form the quaternary amine okay so let's let have a look at the example here for the mechanism for this type of reaction so we'll see how that actually works so you can see here we've got our Hilo alkane which is here and we've got our ammonia molecule which is here and this has the lone pair of electrons to remember from that previous slide where we had a primary a secondary tertiary and quaternary and the reaction keeps going and it keeps reacting to produce these products well this is where we're going to show you how that works so you see we've got our ammonia molecule here and a halogen or alkane and I'll here the welcome so the ammonia first is a nucleophile so it is nucleus lovin so that means it will attack the Delta positive carbon so it attacks that and it tries to form a bond with the carbon and then that kicks the chlorine off so we get an intermediate that's formed and this is an alkyl ammonium salt and it has a positive nitrogen and a CL minus iron that's down here so then what happens is we've got our second ammonia molecule here this is why we use excess ammonia second ammonia molecule here which will then curly you can see this is going to react with the hydrogen and then the electrons from the bond between the N and the H will then jump onto the nitrogen to eventually neutralize that positive charge so this this is why we need that excess cause you've got that second ammonia molecule and then gets involved and then we produce our primary amine and an ammonium chloride salt is then produced so you can see there we are we've formed our primary amine from there not see we've formed our salt now you can see obviously remember we needed an excess of ammonia and the reason why we need an excess because need one here to act as a nucleophile which is this bit here and then here it's actually acting as a base here because it's accepting a proton it's taking that proton so it's acting as two it's got two functions here so you've got it acting as a nucleophile and acting as a base here now you can see that using this method has a downside so the mechanism that we saw that we saw the production of a primary amine however like we say from the previous slide and reactions carries on to produce secondary tertiary and quaternary ammonium salts and so we actually do have an impure product so this occurs because that primary amine that we've just make there still has a lone pair of electrons on that nitrogen so that can act as a nucleophile with your halogen or alkane and you can keep on reacting and reacting until you get to the quaternary salt so the a mean you'd like to say can can react with any remaining of that halogen or alkene to produce that secondary amine and then keep on reacting okay so that's important so this method is a is quite a quick method however you do get a lot of impurities in there you get primary secondary tertiary and quaternary salts so if you're in the business just to make a primary amine this methods not very good because you're not gonna get much primary a good yield of your primary amine okay so let's look at another way of doing it so the second way remember is by reducing nitriles so in this example we're going to look at reducing nitriles using a nickel catalyst and hydrogen gas so you see the cheapest way to make a primary to make primary amines and in industry is to reduce nitriles using hydrogen gas and nickel or we can use a platinum catalyst so this reaction is called catalytic hydrogenation it's got a quite a cool name and unlike using a halogen or our kids that we've seen there and this reaction produces primary amines only so we just get a pure product okay so we're not getting any secondaries or tertiary or quaternary 's we're just getting primary amines which is which is just nice to be honest so there we are here's our nitrile remember a night trial that's got the seed triple bond and bit on the end here so you got nitrile group reaction with hydrogen using the nickel catalyst high temperature and pressure and we produce our primary amine here and the good thing with here is good thing with this is we produce our primary amine but we don't produce any other secondaries tertiary or quaternary so you get a good yield of primary amine so this is really good okay so we can also look at using lithium aluminium hydride and dilute acid so the two ways of producing a nitro obviously that one we use hydrogen so this method is more expensive than using your hydrogen a gas and nickel or platinum catalyst so we're using lithium aluminium hydride here which is very expensive so it's not really an industrial process that's followed to make your aliphatic amine so this reaction is a reduction reaction and we use the reducing agent remember we use hate's and square brackets to symbolize a reducing agent and this is dissolved in a non aqueous solvent so we use a dry ether anything like that so we can't have any water in there so you can see here we've got our nitrile still still the same reagent but this time we're using a reducing agent lithium aluminium hydride for example and we're using a dilute acid and we're forming this product here now the reason why we have a 4 in front of there is because we need to add 4 hydrogen's to this molecule to turn it to this so we can see we've got one two there so there's two hydrogens there and we need to add two hydrogens to the nitrogen on the end here so that's there so that's why we need four even though this is not an actual molecule it's just a CH in square bracket we must still balance it so make sure that you're looking and for the number of hydrogens left and right and it's still balances out okay so we've looked how you make aliphatic amine so this is how we're going to make aromatic Ami's so aromatic amines are made by reducing nitro compounds such as nitro benzene which we've just seen how to make so we've looked at the nitration of benzene so aromatic amines are used to make dye stops and pharmaceuticals so they do have a quite a lot of use in everyday life so the first step in making this is we heat under reflux nitro benzene with concentrated HCl and tin to form a salt such as c6h5 NH 3 plus CL minus so here's our reaction here okay so there's our first step so nitro benzene we reduce it using concentrate HCl and a tin catalyst so then step two is the salt produced in step one is reacted with an alkali such as NaOH to produce an aromatic amine such as fille Nile a mean so you can see here that we've have we've used this here and we use the nitrate sorry than the nitrobenzene to actually produce your aromatic amine here such as phenol they mean so this is all done under reflux because we're using volatile compounds here and you can see here that actually we're using six lots of reducing agents the reason why we have six six here is because we need m2 for every oxygen that comes off we need two hydrogens and because we need to form a water molecule so because there's two oxygens here we're going to form two molecules of water so for the hydrogens go to form there and we need another two to actually bond onto the nitrogen that we've formed here which is our NH two so that's how we make our female a mean because a means have a lone pair of electrons and this allows them to accept a proton and hence they act as a base okay so this is quite standard so a proton bonds to a naming via a dative covalent or a coordinate bond and both electrons in the bond originate from the lone pair on the nitrogen okay so you can see here there's our primary amine which is here okay so that our group and we've got our nitrogen with a lone pair of electrons we add a proton on to that and it forms this dative covalent or coordinate bond here we have an overall positive charge there see and say this is why a means our bases because they accept our proton and the strength of the base is actually dependent on the availability of the lone pair of electrons on the nitrogen so the higher the electron density the more readily available the electrons are okay so what we're talking about here is the availability of this lone pair of electrons and the availability of this is going to be dependent on what is bonded around that nitrogen okay that's going to have a quite a significant influence okay so it's the type of group that has the influence on how readily available the electrons are okay so in order of base strength the stock again the order of base strength is down to like I say the groups attached to it so the weakest bases are actually aromatic amines so that's the ones with a benzene ring attached to it then it goes to ammonia and then you are primary aliphatic amines are stronger bases so let's see why that is the case so here's our different a means we've drawn the structures out here so we've got our aromatic amine to the left here they go and we've got our stronger primary aliphatic amine that's on the side there so benzene is an electron withdrawing group okay so we've seen that remember with and we've seen that with our phenyl molecules so it pulls electrons away from nitrogen and into the ring structure and so the electron density on the nitrogen reduces so the lone pair availability reduces as well so this means that our o matic amines are less basic than other types of amines because of the their withdrawal of electrons into this benzene ring and I've drawn this kind of highlighted structure here just to show where the electrons are moving to okay so obviously a me never sorry ammonia has no groups on there which are withdrawing or pushing electrons in so ammonia just has its and electrons centrally based in the nitrogen there okay and then with an alkyl group so your primary aliphatic amines as we'll see here alkyl groups are actually electron pushing groups so what they do is they push their electrons and towards the nitrogen and that means that the electron density in the nitrogen atom is much higher and therefore they're more readily available them electrons so this means that they're more basic because they're much more readily and they're much more readily available to accept a proton which obviously makes them basic there so you can see the strength of the base is all to do with the group's that's attached to the nitrogen or the electron was drawn are they electron donating you can see that has quite an influence on it okay so amines are also nucleophiles as well as bases so remember they have a lone pair of electrons so they are going to be attracted to Delta positive areas of molecules as well as we've seen for example with our halogen or alkane reactions that we've seen before we can see that we'll see these you know amines and ammonia acts as nucleophiles okay so let's look at solubility of a mean so looks at the chemical properties and how they can be formed and how they react but now we're going to look at the physical properties of a mean so we're going to look at solubility here so a means can hydrogen bond with water and so some have the ability to dissolve in water to form alkaline solutions so just like we looked at the solubility of carbon silicon acids and carbonyl groups we need to also look at the physical properties of a means so the lone pair of electrons on the nitrogen can form hydrogen bonds with the hydrogen atoms on water molecules and so the lone pair on the oxygen can also form hydrogen bonds with hydrogen on the on the on the amine as well so this is AB that's so this is to do with the the oxygen on the water molecule as you can see so here's our is our primary amine here cuz we've got the methyl group that's attached to it this has got a lone pair of electrons on nitrogen and can form a hydrogen bond with the hydrogen on water but it can also form a hydrogen bond with the oxygen on water as well as you can see so we've got both types there and so only smaller a means will dissolve so just like with carboxylic acids so larger ones have larger have longer hydrocarbon components which are nonpolar and these can disrupt the hydrogen bonding within the water molecule so it's all to do with the size of these groups here if these are quite long and have long hydrocarbon chains and they're going to be less soluble than the shorter ones okay and so if the amine is large enough than the London forces between the nonpolar hydrocarbon chain so that's the bits the circled in yellow here so that's these parts here these are obviously the your train of thought here so if the a means are large enough and the London forces have seen these non-polar hydrocarbon chains will be stronger than the hydrogen bonding between the nitrogen and hydrogen between the on the diagram that you can see here so this means that the larger a means will not be able to dissolve so for example if these chains are really really long we have we have our London forces which hold these forces together if them forces are bigger than the interaction between the primary amine in the water then it will be insoluble so basically that's what it means okay so let's look at a means and complex ions now we looked at transition metal and the transition metals topic you would have seen complexes and the look of complex ions so here we're going to look bring that back in again from that topic and look at it in particular to do with a mean so there's a bit of cross over here and the waters is with these with these topics they're never just okay they're in isolation but there's always bridging between other topics so that makes it a little bit easier to to remember I think so a means react with a copper complex ions to form that deep blue solution so remember that from from the transition metal topic so that it's exactly the same this is just effectively summarizing that area of chemistry but it also falls within the a mean chemistry clearly so we can see here we've got a copper complex here so this copper complex is formed by dissolving copper two sulfates in water and you can see we've got all our water ligands surrounding the copper so if you remember that so if we add a small amount of Bute I'll ear mean to copper sulfate solution a pale blue precipitate is formed and we can see it here okay so we're adding a small amount here and so what the amine does is it removes two protons because it's acting as a base removes the two protons and we form this here so we've got M Oh H 2 and H 2 O 4 so you remember that from the transition metal topics like I say but if we add more butyl elements were added in excess then four of the ligands will be exchanged with the a mean and will form in the complex on the right and what we now form is a deep blue solution so you can remember with transition metal complexes we have a precipitate that forms when we have a complex that's neutral so you can see here that we've only added enough a mean here to remove the protons and we formed coppers got two plus charge which is in here and two of the hydrogen's and the water removed to form an O H minus of this effective forms a neutral complex which precipitates out in solution but if we add more then what we do is we form a charged molecule again charged complex here and what we get is a complete substitution of our of some of the ligands on here so we always remember with these ones with the copper ones it's one of the strange ones where you don't get full substitution you get partial substitution so we'll get to the axial water molecules remain but the rest are actually substituted and we get this nice deep blue color and so this is the complex that we form there okay so if the a mean is larger and we may get obviously a different shape complex it depends on the myth if you get a really large ligand you can't fit as many of them around that central meth line you might get something that's more kin to a tetrahedral shape rather than an octahedral shape that we can see that we can see on there okay so acyl chlorides these react with butyl amines and the chlorine is substituted for the nitrogen so you would have seen this in the organic chemistry topic organic chemistry two topic which would be topic 17 and you would have seen this reaction as well so we're bridging into that topic as well so a lot of this is not new this is just drawing other areas from other topics and bringing it into into an amine category so reaction with primary amines produces n substituted a might this is a vigorous reaction that produces a solid white product so let's have a look so you can see here we've got our acid chloride there ethyl I applied and this is reacting with our ami which is this bit here and this is going to form our n substituted amides now remember in terms of the nomenclature of it n is the nitrogen its substituted the substitute bit is because in a traditional a might as we'll see later traditional amides have two hydrogens yes as NH two and that's what a traditional ami it looks like but one of the hydrogens has been substituted for an alkyl groups in this case it's a butyl group so that's why we say n butyl and then it's eath an amide because you've got two carbons here so it's an amide now your butyl ear mean M can also react with the HCL okay so this is this one here there's a butyl a I mean it coming up with this hit shell to produce butyl ammonium chloride so that can react further to produce this salt here okay so just be aware of the reactions that happen here okay so the overall reaction if we Club all of that together we've got our acid chloride which is here reacting with our butyl amine and which is here and then we form our n substituted a made which is here and then obviously our salt is then formed here so this is the overall reaction here and we need two of these obviously two to undergo this reaction okay so it's not too bad okay so we just come to the end of the a mean section for this there's a lot of a mean they really do like a means don't they Edexcel so and more aiming reactions here so just just a few more so a means also react with acids to form alkaline solutions and they form alkaline solutions to say so a means our bases so they do react with acids to form salts however unlike traditional acid-base reactions there's no water that's formed so this is one of the niche things with a means is actually when we take an amine reacts with an acid is still a neutralization reaction but we're not producing water like what you would expect with the traditional acid-base reaction you form salt and water so this one you just form you salt and it's one product and so smaller amines are soluble in water and these can dissolve to form alkaline solutions so remember they they are soluble if you have a smaller i'll kill and alcohol groups on them so in like some bases where there's no H group for example sodium hydroxide a means react with water to produce the O H minor signs that they require and so remember this was in the M acid-base equilibria topic when we looked at this to do with the bronsted-lowry acid and we looked at what makes something a base so this has just drawn some information from that topic and so you can see here and that they produced the O H minus ion which makes the solution basic so you can see in this reaction we've got a primary amine reacting with water and effectively you produce your oh it's minus signs in this way by using water because the molecule itself doesn't have all its minus signs and for something to be basic it must have oh it's minus signs air presence there so this one's just using water effectively to do that okay so remember we said we looked at some of the a mines already in particular and substituted a might so we're just going to look at a mines and a little bit more detail here so a minds are just derivatives of carboxylic acids and they have this functional group of C o NH 2 okay so that's the main difference between a means don't have that carbonyl group near them a might do have a carbonyl group that's the main difference between them so here's a name ID and you can see there's our carbonyl group there okay with an a mean that wouldn't be present so that's the main difference between a might so this is a name ID with your nh-2 group on the bottom as you can see so instead of having the O H it has the NH two so this is why it's a derivative of carboxylic acid and then obviously we have our n substituted a might and we've seen these before so n substituted amides it's just one of the hydrogen's is replaced with an alkyl group as you can see on there which is represented by our okay so acyl chlorides react with ammonia to produce primary amine so remember we looked at this back in topic 17 so all we're doing is bringing some of the information from topic 17 and fitting it in within the amides and a means topic within topic 18 so we can see here the reaction with ammonia produced as a mine so remember this so you've got your acid Clyde reacts with your ammonia molecule so this is ethanol client and this produces your it's an amide so in this case here so you've got your amide and this is a vigorous reaction if you can remember produces HCL white mister fumes acidic and toxic so not a great reaction to use and if you don't have a fume cupboard table so you should use a fume cupboard for an for this type of reaction okay so let's look at again this is a bit of an information from topic 17 organic chemistry to the reaction of acyl chlorides with a means primary amines produces n substituted a might so that's what we've just seen before so there we are so those are s and our chlorides and we've got our primary amine there and that's going to form our and substituted a minor in this case it's gonna be n methyl ethyl amide again this is a vigorous reaction producing white misty fumes okay so and might be familiar with you it depends on which order you've seen the videos or you've studied it in school but yes or college or if you're learning independently that's obviously you know what I mean right okay so we're going to link a lot of these organic chemistry's and again we looks a little bit of this in the last topic so this is topic 17 in this topic we're going to look at polymers in a lot more detail we're going to look at all types of polymers here and look at their reactions and how they're formed so this is going to be quite important so we're going to look at condensation polymers first and they're comprised of three main types so you've got polypeptides polyamides and polyesters so condensation polymerization is where we get two different monomers with at least two functional groups that react together okay so they react when they react we get a link that's made and water is eliminated and this is why we call them a condensation reaction so the link determines the type of polymer that's actually produced now in the previous topic we only looked at polyesters because esters falls into that topic in this one we are going to look at polyesters and look at it in a bit more detail but we're going to look at other types of polyMet as well so you can see the types of polymer are polypeptides which are found in proteins we've got poly amides which are formed by reacting diamines and dicarboxylic acids and then we have polyesters which are formed by reacting the dial and dicarboxylic acids together so you can see here here's some of the examples here so and I'll see polypeptides are found in and the white is is protein of an egg we've got polyimides here which form this type of rope here and then polyesters also used in fabrics as you can see there okay so let's look at poly amides first so polyimides are formed by reacting dicarboxylic acids and die amines together so remember and we must have a we must use a dicarboxylic acid because it has two carboxyl groups on either end of the molecule and that allows us to form a chain and likewise with the diamine so let's have a look at what they are so a my links are formed when dicarboxylic acids react with die amines and so we have to use dichotic silica sand diamonds as they have functional groups either side which allows us to form the chains as I've said before so let's have a look so dicarboxylic acid sounds scary but it's fairly straightforward and it's just a carboxylic acid like to say either side of the group you can see there and then we've got die amines which have an amine group either side of the R group in the middle and then obviously if we react them together we form a poly amide and you can see there's our amide link this is an a might because we've got our C double bond o a carboxyl group na carboxyl a carbonyl group bonded near the NH group which is here so this is an a might link and you can see at the end here you've got your Oh H and your H here these can then react with this can react with the diamine and this can be up with the dicarboxylic acid to extend the chain length so this is a condensation reaction so water is eliminated so that's where the water is removed and obviously that forms your aim I'd link in the middle see it kind of makes sense so will they be in a condensation reaction so let's have a look at an exam all of a polyimide so Kevlar is an example so you don't need to know this specifically it's just really so you can see what it what it looks like but and it's used in bulletproof vests car tires and some sports equipment as it's lightweight but it's strong so Kevlar is made from benzene one for dicarboxylic acid and one for dye amino benzene so you need to know the you know how these can actually bond together so benzene one for dicarboxylic acid is this so you know the structure of that you can draw that and your 1/4 diamino benzene is exactly the same except we have an amine group that's attached to either side of the benzene and then when we join that together we form Kevlar and you'll notice when we draw polymers as you put a square bracket around the edge here we have trailing bonds coming off either side so this shows us that this is what we call a repeat unit and n is the number of is basically however many you've got these in your polymer so we have 2 2 water molecules that are emitted as well when performing this type of repeat unit because we've got water eliminated from the middle here and water eliminated either side okay so like I say so this is the formula and the part of the bracket is what we call a repeat unit okay so let's have a look at another example of a polyamide so this is nylon 6-6 so nylon 6-6 is a polyamide that's used in ropes carpets clothing parachute fabric etc so it's quite a quite a strong fabric and it's made from hexane dioic acid and 1/6 diamino hexane the 6 and the 6 is just a number of carbon chains in each of these molecules so you can see here there's your hexane dioic acid so you've got six carbons in here so that's four there and obviously one either side I think you're getting the hang of this now so one six diamino hexane so you've got your diamine and then if we join all that together we get our nylon 6-6 with the two water that's also produced so you can see how fairly straightforward it is obviously we're removing the water in the middle and forming our aim a my link here okay so polyesters now seen a bit this already the previous topic but polyesters are formed by reactant dicarboxylic acid and dials together so ester links are formed when dicarboxylic acids react with these dials so there's a dicarboxylic acid we've seen that before at this time when so using the diamine we're using a dial so this is just an alcohol group with 208 groups either c 2 h 2o h groups either side so this forms our polyester and you can see we have our ester link in the middle there so we have our carboxyl group at the end here so there it is and then we have our ester link which is over on this side so we our dial which is on this side here so you can see this is a condensation reaction because water is eliminated so this is exactly the same as your a might or ones that we've seen before okay so an example of polyester is terylene and this is used in drinks bottles sheeting clothes for example so it has the acronym PE T so terylene is made for benzene one for dicarboxylic acid and ething one to dial so this is just to give you an idea of what these and what these look like so you can see here your benzene one for dicarboxylic acid so you've seen that before this is reacting with ethan 1 to dial okay and then this obviously forms our terylene products here which is just joining the two together so they might give you in the exam like complicated examples maybe they might give you complicated ones like this and all you have to do is you're just looking for the link an ester link or an amide link take the water out from it and join it together so don't be too startled by examples like this is just showing you how how similar all these reactions are okay so for condensation polymers what we can actually work out the monomer from the polymer chain so the monomer can be determined by finding the repeat unit that we just seen before and we look for either an amide or an ester link depending on what molecule we've got so for example here is a polyester and so we have an ester link that's highlighted there so when we're trying to find the monomer all we do is we break that bond between the carbonyl group and the oxygen there we break that and we out of H or H to either side of the molecule say if it is here so this forms our monomer units and these are the units that we used to make the polymer in the first place so very straightforward okay so condensation polymers these can be hydrolyzed and that means they can be split using water so hydro meaning water lysis meaning to split so this produces the original monomers that we use to form the polymer in the first place and it's just the reverse of polymerization so again it's not - not too difficult here so you can see here's our poly amide a poly amide molecule this is reacting with water because it's hydrolysis and what we do is we form our monomer units back again so in this case it's dicarboxylic acid and dye a mean and so to determine the monomer units produced and remember we break the bond in the middle of the amide and the ester link of the repeat units so we need to identify the repeat unit and then we add OHS and hate to each of the monomer units as we've seen before and remember for polyester we produce dicarboxylic acid dicarboxylic acid in the dial and for poly amide we produce a dicarboxylic acid and a dye a means to just remember that okay so let's look at another type of polymer which are amino acids now amino acids have an amino group which is NH two and they have a carboxyl group which is co8 so you can see here you have a carboxyl group and we have an amino group and so this is a carboxylic and this is an amino acid so amino acids are amphoteric and what this means is that you have acidic and basic property so they can now they can act as both and so amino acids always have an organic sidechain and this is represented by our which is on here with the exception of glycine where R is actually a hydrogen so so that's so that's the only exception there and so amino acids are chiral as you may have seen so they have four different groups around it as you can see this one's got one two three four obviously with the exception of glycine because that would have a hydrogen there and that means it would only have three different groups that's doesn't make it Kyle so what that means is most amino acids though and can rotate a plane polarized light so amino acids are named in two different ways and they have a common name and a systematic name so this is using our upat rules and it's fairly straightforward so step one macht looking for is finding the longest carbon chain so in this example the longest carbon chain is three as you can see here so got one two three okay so don't forget to count that carboxylic acid carbon as well so this is propanoic acid and then step two we just number the carbons so carbon one is in the carboxyl group members who always number from carbon one so you remember from topic 17 in organic chemistry two so when we looked it we looked at naming carboxylic acids to be always named from carbon one in the carboxylic acid is so the carbon in the carboxylic acid is carbon one step three we note the number where the nh-2 group or groups sit and here we can see that the NH the nh-2 group sits on carbon two so we call it a me know when my naming the amino acid okay so step four we name any other groups and that are not NH two in the standard way so for example Oh H we call that hydroxy so we just name it so the name of this is two amino propanoic acid so it's pretty straight forward not too not too difficult to see calling it an amino acid helps to sharpen your mind to say right it must be amino and then acid so mister the amine group then the assets that we named after that okay so we're going to look at am M no acids and behave in them or how they behave as spritzer ions and so it's a little bit of German that's if you do German so you'll know what it's Rhine is and so as bitter wine it's just a molecule with both positive and negative ions so this bitter ions only exists as the amino acids I saw electric point in case we wouldn't look at what the isoelectric point is and so that is just the pH at which the average overall charge is zero so this is dependent on the R group okay so let's have a look so here we've got a zwitterion okay so were two ions effectively so a single charge negative charge and a single positive charge so this bit rind is likely to be formed to this this is fit Ryan when when at a pH at the isoelectric point so both the carboxyl and amino groups are ionized okay so both have got a charge so at low PHS so in acidic solution so if the pH is lower than the isoelectric point so which would be stated so each amino acid has an isoelectric point this should be in a data book of so you'll be provided with that so if it's the pH is lower than that isoelectric point then the C Oh Oh - group this bit here is likely to accept the proton okay so it's going to receive the proton there at low pH because obviously there's loads of H pluses and then likewise at high PHS if the pH is higher than the isoelectric point then the NH - sorry the nh3 here is likely to lose a proton to form NH 2 which is on this side so that's just a pendant on if the pH is above or below the isoelectric point which of course you'll be given you're not expect to remember them okay so we're going to look at a thin layer chromatography so chromatography is an important method of separating substances out so thin layer chromatography allows us to separate and identify amino acids as they have different m solubilities so this is about trying to identify these amino acids so thin layer chromatography also known as TL see how lovely uses a stationary phase of silica or alumina mounted on a glass or metal plate and a pencil line is drawn and drops of amino acid mixtures are added so you can see others or drops of amino acid so we have a mobile phase which is the phase that moves so this is liquid solvent and then we have our stationary phase this is the bit that doesn't move which is this plate here and so that's bit of silicon dioxide or aluminium oxide and then we put a glass lid on top and that just prevents our solvent from actually evaporating from this so we place the plate in a solvent and the baseline must be above the solvent level if it isn't then we're going to get our substances effect that we dissolve and into the solvents and of course we well obviously we don't want that at all so we leave until the solvent is moved up to near the top of the plates so up towards the top here we remove the plate and mark the solvent front and we allow that to dry and then it works by the amino acid mixture spots effectively they're dissolving in the solvent some of the chemicals in the mixture mean that may not dissolve as much and actually spend more time stuck to the stationary phase but either way what we're going to be left with is a chromatogram of migrated amino acid spots moving up this plate and so we can identify the amino acid positions on the chromatogram because we can measure it and we're going to look at how we calculate our F value on the next slide okay so amino acids can be identified by calculating the RF value from a chromatogram so you've got you kumata gram already established and then we're going to calculate the RF value so the number of spots on the plate tells you how many amino acids make up the mixture okay so amino acids can be identified by calculating the RF value so if we've got four three four spots on there but you've got for me--not acids but that doesn't actually tell us what amino acids there are so we have to do a little bit of maths and this is done by Clayton the RF value and comparing these with a library of knowin RF values so you can see here we've got our chromatogram we've got our solve in front which you've drawn in and we've got the distance traveled by the amino acid and spot which is moved on here you might have a few spots on here but this is just for simplicity purposes I've just put one in there so the RF value is calculated very simply and it's just the distance traveled by the spot which is represented by the red arrow divided by the distance traveled by the solvent which is the purple arrow here so that's up to the solvent front and so the RF values are fixed for each amino acid so they're the same however and if temperature or the solvent or the makeup of the TLC plate changes then we're going to get different RF values so RF values are only true for am certain of a certain amino acids if the conditions are kept the same as you can see so there is a lot of factors that you must keep the same okay so we're going to look at these type of reagents now these are funny reagent these are called grignard reagents now grignard reagents are vital to help with carbon-carbon bond formation which happens all the time in chemistry and without grignard reagents we simply wouldn't be able to do it because these chemicals are really to try and make a carbon-carbon bond needs a lot of energy and it's really difficult to do because they're generally unreactive li alkanes for example so grignard reagents are organo magnesium compounds and they are made by reacting a halogen or alkane or hilo alkane with magnesium in a dry ether so here's an example here so you've got your halogen or alkane reaction with magnesium and this forms your organ or magnesium compound which is here and so we have like a specific example so this is hora same for example reacting with magnesium and this forms our organ or magnesium compound or our grignard reagents so let's have a look at the reaction with carbon dioxide so carboxylic acids can be made by we it's in a grignard reagent with carbon dioxide so we can see it occurs in two steps so we have a dry ether and we bubble carbon dioxide in the grignard reagents and then we add dilute acid to the solution after that okay so let's have a look so here's our grignard reagent here and this has got the alkyl group that we want to that we want to add on we've got our carboxylic acid oh sorry carbon dioxide here we're going to add a driver first then we add the acid afterwards and then what we form is our carboxylic acid which is here so you can see where I've color-coded it here so you know that our group which is here and the carboxylic acids so the carbon dioxide is effectively this bit here and obviously we add the the hydrogen here which has come from the acid and then we form I'll see how our by-product Ritz's on the side there so we have effectively have formed we've got a new CC bond is formed when the are here breaks off the grignard reagent and bonds with the carbon in a carbon dioxide and obviously this in turn then breaks the C double bond o bond so that breaks this bond here and so that was a double bond now that's a single bond to form this group here and obviously the hydrogen then adds on afterwards that's pretty clever because we've just made a carbon-carbon bond and that's really difficult without without this grignard reagent to do that so finally like say the HCL protonates and forms the carboxylic acid so if that was that was the hydrogen adding on there okay so we can also use grignard reagents to do carbon-carbon bond synthesis by a reaction with carbonyl compounds which we've seen already in the previous topic which is topic 17 and so alcohols can be made by reacting grignard reagent with aldehydes and ketones so again happens in two steps so driver bubble the carbon so bubble the the aldehyde or ketone should I say and the grignard reagent rather than the carbon dioxide and we add a dilute acid to the solution so you can see here so instead of this so we're not bubbling carbon dioxide that was a that's an arrow all changed and obviously were bubbling through our aldehyde or ketone or carbonyl compound so reacting that with that dry ether then acid and you can see again I've marked it up in red so you can see what's going on so the R is effectively added to the carbon here so that just adds on to there and then the hydrogen from the acid turns it into your alcohol which is here and then obviously we have mg be our CL as our by-product there so your new CC bond is formed when the Arbit breaks off the grignard reagent bonds with the carbon in the carbonyl group and this obviously in turn breaks the C double bond o bond and o bond here to form your alcohol so this is very similar to car carbon dioxide reactions that you've seen already okay so again that's the protonation using the acid okay so here this is where we're basically gonna take that's all the organic chemistry really that you that you need to know all the basic reactions and now what we're gonna do is go through a summary face and we're going to summarize all the functional groups the reaction types and go through some organic synthesis summaries as well and then finally we're going to look at some practical techniques towards the end of the video so it is a very long video as you can as you can see so and functional groups okay so we need to know that following functional groups their properties and their typical reactions so we've come across a lot of functional groups over organic chemistry so this is just a nice summary to look at so alkanes they have a CC single bonds they're unreactive and non-polar bond and type of reactions that they need to undergo a radical substitution so that because they're pretty unreactive so we need to form radicals and alkenes have that double bond I'll put a bit of a joke to you just just a break it up a little bit as opposed why our Jordi's so good at chemistry because the alkyne yeah that would only come from a Geordie wouldn't it anyway so alkenes the properties electron rich double bond so got that double bond in the middle there and it's a nonpolar bonds there's no polarity this typical reactions electrophilic addition so we use an electrophile remember and it adds onto that double bond aromatic compounds so properties delocalized electron ring and they're very very stable as you've seen the reactions are electrophilic substitution and alcohols properties and we've got lone pair on the oxygen that can act as the nucleophile polar CE o H bonds typical reactions astera fication and nucleophilic substitution and also dehydration elimination and you could have Felix substitution reactions as well so the lot to do with alcohols and hero alkanes or halogen or our kids they have a polar CX bond obviously with a halogen attached to it and typical reactions they undergo nucleophilic substitution and undergo elimination reactions as well to form your alkenes nitrile reactions so the properties electron deficient carbon center because you've got that nitrogen pulling the electrons towards itself typical reactions they undergo reduction and hydrolysis reactions as well and a means so CN are group remember so they have a lone pair in the nitrogen can act as a as a base and a nucleophile so it has it has two functions they're also typical reactions nucleophilic substitution and they can also see undergo neutralization reactions because of their basic properties aldehydes and ketones they have the carbonyl group which is polar see if that Delta positive and the carbon there and which is on this but here's he Delta positive carbon a nucleophilic addition oxidation of aldehydes and reductions so these are involved in a lot of reactions as you've seen as you seen before and then carboxylic acids and so they have the carboxyl group the C double bond sorry C double Oh H group which means that it's a carboxylic acid and the properties it's electron deficient with that carbon center in the middle so very similar to carbonyl compounds and typical type C reactions are esterification and neutralization reactions Esther's so Esther's they have that electron-deficient carbon Center still so and that's quite important for Esther reactions such as hydrolysis which is breaking up of the ester using water so hydro meaning water lysis mean it's a break acid anhydride 'z have seen some of them particular making make an aspirin we use the unhide ride so they have an electron deficient carbon center and I'll see that's typical reactions as esterification reactions so in particular like I say making em aspirin am acid chlorides or a surprise is also known as and have an electron deficient carbon center remember so that's right in the middle there and it's it's surrounded by oxygen and chlorine which are very electronegative so these undergo quite a few reactions such as nucleophilic addition elimination reactions condensation and friedel-crafts isolation reactions as well and I think we've heard carboxylic acids let me just check we have so we've had carboxylic acids there okay so we know about that one so I'll get that one removed because I don't know about carboxylic acids twice I just got a bit carried away there think with that one okay so what we need to be able to do and the key thing with inorganic reactions is when you're being given when you're given a lot of molecules and some of these molecules are massive and they've got loads of different functional groups attached to them and the key thing with organic reactions is spot the functional group so it's trying to find the functional group and know the types of reactions that we've seen all the way through because you've now seen all the organic reactions that you need to know for like for a level so it's about trying to spot these functional groups and knowing what type of reactions you can do with them don't worry about the bulk of the molecule you'll need to know a tiny bit so spotting the functional group is actually really important so we're going to look at some examples here and they're quite big molecules that it's done deliberately okay because the whole point is to just we'll look and for the specific functional groups so see if you can spot them as well so here we've got paracetamol so this is obviously a painkiller so see we can try and find the functional groups and this so you can see we've got a phenyl group which is that and we've also got an amide group which is there so we've got two functional groups there so we can immediately switch our brains on to a mild reactions and phenol reactions what about adrenaline so have a think so have a look see what functional groups you can see in there well you can see we've got a phenol group again we've got an alcohol group and we've got an amine so we've got three functional groups in that one so we can apply any types of chemistry to them even though it's got two groups on that benzene on that phenol that's still classed as a phenol okay what about this one this is a an active ingredients that ethyl cyanoacrylate is used in superglue to see if we can work out whether functional groups are on this one so this is gonna be over here nitrile and we've got a alkyne aisle as well this is just a double bond and alkyne i've got this which is an ester so you can see what loads of different functional groups in there and about what we can do with them so for example we can do hydrolysis of the ester you know we can do we could turn this amine into no we can't I was gonna say would turn it into well we cannot yeah we can do it aiming into an A might so we can do that so got loads of different reactions here and obviously phenol reacting that with a base to form a salt so we can do loads of things so that's the whole thing is about trying to look for functional groups okay so we're going to look at some reaction types and these can be split into seven main types of reactions so the first one is an addition reaction so addition reaction a double bond is broken and two molecules join to form a single products okay so the functional groups involved are generally alkenes and carbonyl groups here as you can see so these are generally addition reactions substitution reactions this is where a functional group is exchanged for another one and so the functional groups involved are your halogens you've been GHS substituted and alcohols elimination and dehydration reactions so double bond is normally formed with these types of reactions so a functional group is removed and released as part of a smaller molecule so types of functional groups have moved our hydrogen halides for example and water molecules this is an example of elimination reaction condensation reactions so this is when two molecules join and a small molecule is eliminated so the functional groups normally involved with condensation reactions are things like acid chlorides carboxylic acids amides and alcohols so you've seen all these reactions before this is just summarizing all of these hydrolysis is the other one so this is where two smaller molecules are formed by splitting a larger one with water such as breaking polyamides and polyesters and so we get the various different types of functional groups that involved regarding hydrolysis so remember hydro meaning water lysis mean and split oxidation reactions so normally means the gaining of oxygen or the loss of a hydrogen in reactions however theoretically it is the loss of electrons remember oxidation is the loss of electrons so oil-rig and so the functional groups involved are very typical primary alcohols as you can see here you go to primary alcohols go into an aldehyde go into a carboxylic acid or secondary alcohol go into a ketone and the final type of reaction type is our reduction reactions so reduction reactions is the gain of electrons remember so oil-rig and this is basically just the opposite of oxidation so you've got a carboxylic acid go into an aldehyde and a primary alcohol or a ketone going down to a secondary alcohol so there is seven reaction types okay so with this one what we're going to do now is we're going to look at organic synthesis we're going to pull all of them different things together and what you'll be able to do is take the information that you've learned for organic chemistry and put it all together to form a synthetic route because this is vitally important for chemists to be able to use their knowledge to actually make something from it so we need to know your aliphatic organic chemistry reactions so what I'm gonna do here is I'm gonna go through each one of them so I'm going to put up the arrow and it might be a good idea for you to practice this and the key thing is to practice it over time because there's no way you could look at all this and do it within an hour just unless you've got superhuman brain and so what we're gonna do what I thought would do might make a little bit more interactive is to when I go through these I want you to these are all the reactions need to know for Edexcel okay so what I want you to do is to you know if you want to pause the video so I'll release an arrow pause the video so you can get the reaction conditions right the temperatures and the reagents that we use and then unpause the video and then what I'll do is I'll release the the answers on here so see if you can go through see how many you can get and build it up so let's start with the first one so this one here alcohol to a light so pause the video and see if you can work out what's required to turn our culture outside okay well the answer is potassium dichromate sulfuric acid overheating a primary alcohol in a distillation kit to get your aldehyde so what about aldehyde to alcohol so pause it and see if you can work out what the answer is okay well this is sodium borohydride set at a pH for in methanol and water what about aldehyde to carboxylic acid well this one's dichromate so potassium dichromate sulfuric acid and it's all done in the reflux what about alcohols ketone well this one's potassium dichromate but we're in sulfuric acid and heat but we using a secondary alcohol for this one service you perform in a ketone in a reflux kit as well about ketone to alcohol well this one's sodium borohydride in methanol and water so what about alcohol to alkene so this one is concentrated sulfuric acid and for vorak acid and heat so either one of them conch sulfuric or phosphoric and heat so what about alkene to alcohol well this one's steam and phosphoric acid catalyst h3po4 and 60 atmospheres and 300 degrees Celsius so a little alcohol to hear the well kin well this one is user sodium halide so na X sulfuric acid and it's going to be done at 20 degrees Celsius so what about halo alkene to alcohol well this one's going to be warm sodium hydroxide and water and it's going to be done under reflux what about alkane to Hilo alkane this one's going to be halogen and we're going to use UV light that's the radical formation one so what about alkene to he'll walk in well this one's going to be hydrogen halide and it's going to be a 20 degree Celsius so what about here while K into alkyne well this one is TAS iam hydroxide ethanol and reflux services of see an elimination reaction we're removing to form your alkene what about alkene to die halo alkyne die halo alkyne to the same well this one is we're using a halogen and we're going to react that with 20 degrees so that's like bromine water a depolarization of bromine what about alkyne to dial okay this one's gonna be acidified potassium manganate kmno4 which it should be a small fault there at 20 degree Celsius so we'll get that changed and then what about alkene to alkyne so this one should be hydrogen a nickel catalyst and at 150 degree Celsius and then what about alcohol to I order alkane well this is iodine so i2 and again that should be a small to red phosphorus and obviously under reflux and carboxylic acid to alcohol well this one's going to be lithium aluminium hydride and this obviously forms your primary alcohol from your carboxylic acids are using a reducing agent for that one okay so there's a few more here so you can see there's no way you'd be able to know all of these off by heart you know right from the off so you need to give it loads of time you know build it up every week see if you can get 10% of them right that's fine and then see if we can do the following weeks you can get 15% writes and then the following week 20% and just keep on going up them keep practicing okay so let's do the same again so here a while K and this is taken from the previous slide I couldn't fit it on and one and go into a nitrile so this is potassium cyanide ethanol and reflux and what about nitrile two primary amine well this is lithium aluminium hydride or dilute sulfuric acid we can use or we can use a hydrogen nickel platinum catalyst to the high temperature and pressure or we can use sodium ethanol or reflux you can use either one of them okay so what about halo al-kidd two primary amine okay well this is ammonia nh3 and heat so what about nitrile two carboxylic acids that was from the previous slide okay well this one's dilute HCl and reflux so what about here the alkane two carboxylic acids Willis ones using magnesium a dry ether and carbon dioxide in dilute acid so this is your a grignard reagent so what about aldehyde or ketone two hydroxy nitrile well this one's potassium cyanide sulfuric acid and it's a twenty degrees Celsius so all about ASA applied to carboxylic acid okay so this is water and it's a twenty degrees Celsius so then what about a carboxylic acid to a Sall chloride are supplied well this one were using socl2 to get that reaction out and then what about aldehyde or ketone to form your ester so this is going to be concentrated sulfuric acid and alcohol heat and catalyst so effectively to to form your ester there and then ester to carboxylic acid so this is going to be dilute sulfuric acid water reflux and catalyst or we can use dilute sodium hydroxide and reflux so what about Esther to alcohol this one's going to be dilute acid or alkali and this is going to be done under reflux so what about alcohol to Esther well this one's going to be a carboxylic acid acid catalyst heat or a tile chloride depending on what you would like to use there and then what about acyl chlorides - primary amine this is going to be ammonia and it's going to be at 20 degrees Celsius okay so we're going to look at so they're all the aliphatic ones that you need to know and we're now going to look at your aromatic ones so I'm just going to go through these ones just so just so you know the reactions of them of course so we're gonna start with benzene so benzene to form nitro benzene is nitration so we're going to use comp sulfuric acid and nitric acid at under fifty five to get mono nitration remember if you go over fifty five degrees you're gonna get loads of nitrogen and reduction will give us a phenol ear mean so this is using coke konk HCL tin and reflux and we add sodium hydroxide and that will give us obviously a reduction reaction and then isolation so this is one of your friedel-crafts reactions so using an acid chloride and aluminum chloride halogen carrier as catalyst and we're gonna do it in reflux under anhydrous two conditions to form our female ketone so benzene again so to form a hero benzene this is holid halogen ation so all we do is we add halogens or x22 aluminium chloride catalyst and under warm conditions and so it I'll kill benzene so alkylations or halo alkane again we're going to use a halogen carrier alcl3 catalyst and alga be done the reflux looking at phenol reactions so phenol form and sodium phenoxide is using sodium hydroxide at 20 degrees Celsius and phenol to form two four six try bromo phenol we're gonna use bromine water which is BR two and twenty degrees Celsius and we'll get multiple multiple substitution there okay so organic compounds these can be identified using molecular and empirical formula so we're going to look at identifying some of these substances this is a little bit of maths involved in this section here so the actual number of atoms is so the actual number of atoms in a molecule or an element is the molecular formula so for example we're going to look at example for ethane is c2h6 so this actually tells you how many atoms are in there so the empirical formula and is the simplest whole number ratio of atoms in a compound and it's given for example and for ethan and the empirical formula is ch3 so we're just given the simplest ratio of carbon to hydrogen within the empirical formula so the empirical formula is the simplest whole number ratio of elements in a compound remember so we're gonna have a look at an example of how we can calculate empirical formula so a compound contains twenty three point three percent magnesium 30 point seven percent sulfur forty six percent oxygen and what is the empirical formula for this compound so you can see here the first thing we need to do is write out the elements involved so we've got a magnesium we've got a sulfur and we've got an oxygen because this is what we've been told at the top and so then what we're going to do is write out the percentages as masses so you can see we've been given the percentages of twenty three point three thirty point seven and forty six percent or would you take the same numbers and just put G at the end of it so we're just converting them as grams and then we divide these by the relative atomic masses to get the number of moles so the relative atomic mass of magnesium is twenty four point three of sulphur it's 32 point one and of oxygen is 16 and obviously we get the number of moles that's written down there we then divide all of these by the smallest numbers to get by the smallest number of moles so for example here we had naught point nine six s that was smallest so we divide all of them by a naught point nine six and we get our ratio of one two one two three and obviously from that we can then deduce our empirical formula as mg so3 so that's the simplest whole number ratio here now you can see to work out the molecular formula from this all we do is we work out the molecular the M R of the empirical formula and we divide by the M R of the molecular formula and we should get a number and we use that number to multiply all the atoms in the empirical formula to get your molecular formula so for example if we divided the number and we got two then we just multiply all of the atoms in the empirical formula by two so it would be mg 2 and s 2 or 6 as an example let's say sometimes you empirical formula can actually be the molecular formula as well so for example if we work out the relative molecular mass of this and divided by the world from molecular mass of the actual mass of the compound the molecular formula and we get 1 then it means we multiply everything by 1 we're just left the same formula so yeah so that's how you work that out so empirical formula can also be used to work can also be worked out from combustion analysis as well of burning an organic compound completely so let's look at an example so hydrocarbon combusts completely to make naught point 8 far an L naught point 8 4 5 grams of carbon dioxide and nought point 1 7 3 grams of water so what is the empirical formula of the hydrocarbon so here we go the first thing we need to do is we need to write down our headings which is water and carbon dioxide as our headings because these are the combustion products and then we write the masses of each molecule underneath so because we've got no point 8 4 5 of carbon dioxide and naught point 1 7 3 grams of water we then divide these by relative molecular masses to get the number of moles so the relative molecular mass of carbon dioxide is 44 and the relative molecular mass of water is 18 so we get the total number of moles for each naught point naught 1 9 and naught point naught naught naught 96 so one mole of carbon dioxide has 1 mole of carbon atoms so the original hydrocarbon must have naught point naught 1 9 moles of carbon atoms so it must've because this is the only source this is only where it comes from and so one mole of water has 2 moles of hydrogen so remember okay so original hydrocarbon must have had naught point naught naught 96 times by 2 which is not for naught 192 moles of hydrogen atoms so remember the carbon in the carbon dioxide and the hydrogen h2 L can only come from the hydrocarbon ok so then once we've got that information we then now divide and the number of carbon and hydrogen atoms by the smallest number of moles so you can see yeah that's not point naught 1 9 so we're gonna do not put naught 1 9 divided by 0.01 9 gives us 1 and then that's 1 so then we can work out an empirical formula here as C H okay so combustion analysis and can also be given as volumes by using molar ratio of gas volumes and we can work out the molecular mass of an unknown substance so let's have a look so we've got 25 centimeters cubed of an unknown hydrocarbon X was burnt completely with 125 centimeters cubed of o2 and 75 centimeters cubed of co2 was produced so here we're going to calculate the molecular formula of hydrocarbon X so we're going to use the volumes given to create our molar ratio equation so we got the volumes here so we're going to put 25 X + 125 o 2 equals 75 or producer 75 co2 and NH 2 X we don't know what this value is so let's you just put the volumes in there the next thing we need to simplify that because they're far too big obviously simplify the equation by dividing by the smallest number in this case it's 25 and that gets us something a little bit more manageable so we've got X 5 or - 3 co 2 and NH 2 L so then now we so we see we can have or we have five moles of oxygen producing three moles of carbon dioxide and n moles of water and any oxygen produced that is not accounted for in co2 has to be in the water okay so that's the only other place it could go so n in that case is going to be 5 times 2 okay which is the amount of oxygen here minus the amount of oxygen in here and that will tell us what's left here so the answer is 4 so now we have the following equation which is X 5 or 2/3 co2 + 4 H 12 so we can see the last step here so the carbon in co2 which we can see is 3 okay so yes we've got 3 carbons and the hydrogen H 2 O so we'll have 8 of them because it's 4 H 12 can only come from the hydrocarbon so we can now work out the formula of X so C 3 H 8 and it's as simple as that okay a little bit of algebra there but remember the first thing you need to do is add all of you your masses in there and put them in front simplify it work out and you know see the number of moles of water and then we use the hydrogens and oxygens and hydrogen's and carbons that we know from our products to work out the molecular formula of our reactant okay so this is the last part the last parts of this video looks at practical techniques so ways in which you can make things measure things purify things and test things so we're gonna start with reflux first so reflux is a technique and we've seen this already in organic chemistry all of this is used in organic chemistry so reflux is a technique you use when you want to heat a volatile liquid so reflux allows us to heat something really strongly without losing it into the atmosphere and effectively it works by heating a volatile compound in here it evaporates at the column and then condenses back down and we use this lie big condenser to do it the library condenser she has water going in here and then water coming out here we've got its surrounding this inner tube in the middle there and effectively this condenses back down into the round fob bottom flask and that allows it to react further and so as we're using flammable liquids heating has always done either via water bath or heating mantle because what we don't want to do is use a naked flame near anything that could catch fire the rise you really do have a bit of a problem on your hands if you do that okay so let's look at enormous distillation so distillation is used when we want to separate substances with different boiling points so this is ideal for example for extracting an aldehyde so gently heating the mixture will result in the compounds separating out in order of boiling point and knowing the boiling point of the chemical you are you want to separate will allow you to decide how you are going to separate your compound okay so if your compound is a lower boiling point then your starting mixture then you heat to the temperature of the boiling point of your compound you want to separate and we collect that in our vessel because obviously that's the first one that's going to boil first that's going to come out of this and this flask here condense against the condenser here turned back into a liquid and we can collect it back in the vessel at the end so if your compound has a higher boiling point then you're starting than the start mixture then you heat to the temperature the boiling point of your compound you want to separate and your compound will remain in that flask so obviously we evaporate off the one that we don't want that goes into the separate flask on the right and the ones that we do want will remain in the fast because as a higher boiling point and so distillation like say is useful we'll want to extract a chemical before it reacts any further so for example oxidizing primary alcohols to an aldehyde and we want to extract that aldehyde straight away so if we just leave it in there to out further it will oxidize further to a carboxylic acid so distillation is good for that okay so steam distillation so steam distillation is used when we want to separate substances with high boiling points or the ones that decompose when they're heated so for example if a product is immiscible with water and then steam distillation is used to separate compounds that couldn't be done under standard distillation so you can see the steam this is the first bit is produced and is pushed through an impure sample so it's pushed through here as you can see and the steam lowers the boiling point of the immiscible product so that's to put the can't mix and allows for it to be still out of the mixture before it actually decomposes so that's pretty clever and the second and so the second thing is that this method is also used as useful for substances we want to separate at high boiling point as the steam reduces this so if and this is lower then it means we are able to separate them as normal so if the substance this is the second second party of the day of the apparatus so if the substance we're trying to collect is less volatile than the Constituent substances were trying to separate from in the words that's in here then the desired product will evaporate out the flask with the steam so that will come out of here and down in here with the steam which comes out at the bottom and then and this is obviously conduct condensed and collected in the separate flask at the bottom there now the key thing here is now we have a mixture of steam and our volatile compound this there's obviously mixed in here so we can separate this by using the separating funnel so if the product is partially miscible then we may have to use solvent extraction and we're going to look at that now about how to do that so in other words if the solvent here is actually mixes a little bit with the water then we need to do a separate technique it's not quite as simple as just stamp decanting it from there so separation purification so separation techniques are used to remove impurities that are dissolved in waters that could be as a result of that previous technique that we'd seen there so separation so this is a useful method when we add the products from the distillation what we seen before into a separating funnel shown on the left here and we add water to dissolve soluble impurities and create an aqueous solution so we add water in here that dissolves to solve the soluble impurities in here so that that's poured out through there and then after allowing the solution to settle we get two layers that form we get a top layer which is your impure products that's what you're wanting and the bottom layers the aqueous layer containing them soluble impurities and we drain that off or should we drain that off down here and I've got to remember to remove the stopper because if you have the stopper on there it won't absolutely come out here so remember to remove the stopper and then drain that off and then we now need to purify our sample through two further steps so we need to wash it and we need to dry it so this is our sample here cuz it may slum impurities in there so and so we're going to remove impurities by washing first so there are or there may be some unwanted impurities still in that solution so we need to remove these by washing the product with another liquid so this is what we call washing so if for example we had a carboxylic acid as an impurity we add sodium hydrogen carbonate to this solution obviously this would react with that to form your salt and carbon dioxide gas the salt would dissolve in that eight crisps layer that we've just added and that would leave our purified organic compound in the top layer so so that's that would be an ideal way of removing say carboxylic acid impurity and we can also remove water as an impurity by draw so we take that impure product from the separating funnel and we add it to the round bottom flask so for example we can add anhydrous calcium chloride this is a dehydrating agent remove and it will remove the aqueous substances that may be still remaining in your sample we invert the fasiq a few times and we leave it for 20 to 30 minutes to allow it to separate back out again and then what we can do is we can filter this we can use fluted filter paper to increase the surface area to filter that solid drying agent out of your substance and just to try and get that so all these techniques are about purifying your sample that you've just made - removing these impurities so filtration so we're gonna look at two types gravity filtration is used to separate solids from liquids so this method is used if you wish to keep the liquid part of our substance so we dispose of the solids so very simple we just place a bit of filtered filter a fluted filter paper which is just Constantine it into the funnel we dampen it just to create a bit of a seal we pour the reaction mixture into the funnel and we do that slowly because we don't want obviously to overflow out of the funnel and then gravity will just pull the liquid through into the vessel below and obviously our solid and will remain in the in the filter paper and we can purify that liquid that we've collected obviously and we can dispose of the solid in the filter paper appropriately and the other way of filtration is using something called vacuum filtration and this is useful for separating liquids from solids so we use a book and a funnel and filter paper and we connected up to a vacuum system normally you just plug it into a tap you have a contraption which creates a negative pressure so it helps the vacuum is used to help separate the liquid and solid components thoroughly we use a filter paper here so we use a disk instead and we just dampen it slightly in the Buchner funnel to create that seal and we pour the reaction mixture into the Bhakra funnel and with the vacuum line on and the vacuum creates that reduced in the flask it pulls the liquid through and the solid will be left in the in the book no funnel at the top okay so fairly straightforward you would have seen this before and obviously the solids that we've collected in the top there we can re crystallize that and to purify it further okay so let's look at recrystallization so recrystallization is a method used to purify solids and the solvent has to be chosen very very carefully so all we do is we add just enough hot solvent to allow the impure solids to dissolve and so this will mean that you have a saturated solution of your impure product it's very important you just add just enough solvent to allow that to dissolve so you allow that solution to cool down slowly and what we'll see is crystals just starting to form as it as it cools down and your impurities will actually remain dissolved in the solution as there's a smaller quantity of them so they'll remain dissolved and it takes a lot longer for them to crystallize out so the crystals you're forming will be actually your product that you want and so we filter to get your solid purified crystals we wash them with very cold solvent to dry them off because we don't want them to dissolve so you must use Omega and ice cold solvents but we've got to use our solvent carefully though to choose it carefully so we want our impure solid to dissolve fully in hot solvents but we want it to be virtually insoluble in a cold solvent we don't want our solid to just dissolve so if your substance won't dissolve in the hot solvents then obviously you can't you can't filter it and obviously that's not a good idea you want your solid product okay so let's look at the we've made our solid products and now we want to know how pure it is and we can use and boiling points to measure the purity of something so measuring the boiling point of your substance can help to detect impurities in there so we can determine the boiling point of a liquid for example by using a distillation setup on the left so this is how we're going to determine the purity of a liquid if we're collecting a liquid so if we gently heat the sample we can measure the temperature at which it distills using the thermometer in the equipment and so this is the boiling point and then what we can do is compare the boiling point from this against the data book value to see how see how it compares and basically if your sample does contain impurities then your boiling point is higher than what's recorded in the data book so your sample and boils over a range of temperatures is another one so if you have a sharp temper boiling point if it boils at a very specific temperature that's fine if it's boiling over a range temperature range of temperatures then clearly that's not that's not going to be much good and because you contain you may have impurities in there so there's two ways so you if the boiling point is higher than what's recorded in data book then you have impurities and if the boiling point is not excuse me if the boiling point is not sharp then then obviously it will have impurities there as well so what we've got to be careful of is that various organic compounds have the same boiling point so it's not an exact science here and so we need to use other and other analytical techniques such as mass spectrometry to spot any impurities as well in our sample okay so the purity of a compound and they say can be determined by measuring the melting points so this is for solids in particular so all we do is we add a sample of the solid product into a capillary tube which is just a really fine tube you may have used them in school or college and you seal the end of the glass tube and the Bunsen flame and then you gently tap the solid product into the capillary tube very very fine tube and we put it into a heating elements of a melting point apparatus that looks like this and then what we do is we slowly increase the temperature of the substance until that starts to melt and there is a temperature range from when the solid just starts to melt to when it fully melts and we can see that by looking into the viewfinder here and we get a magnified view of the solid in the tiny little tube to see how that melting and see it melting as it goes through and then what we can do is compare the melting point against the data book values okay and then basically if your substance contains impurities the melting point will be lower and if the temperature and the temperature range will be larger as well so we're looking for this is ideal if we want to test the purity of the solid that we've produced and that is it okay this is a massive massive video okay so but you can take bits and pieces from it you can obviously clearly it's designed so you can either have a full summary of topic 18 or you can jump to different parts of the video to get the bits that you need but I do have whiteboard videos that look into that as well like I say there's a full range of videos for Edexcel on a little chemistry YouTube channel that offer free have a good look there all I ask is you hit the subscribe button and just to show you support that'd be fantastic and also the slides that you see here they are available I've still got a little bit and sorted out on them as well but they are available if you just click on the link in the description box if you had to purchase them there they're great value but that's it okay bye bye