Transcript for:
Understanding Hybridization, Alkenes, and Benzene

so foreign tk remember it's c686 uh alternating double bonds that's one way to represent it like in cambridge represent uh what happens to hybridization of carbon tk uh you must know that there is a thing called sp3 hybridization where carbon is making four bonds and if it's making four bonds though uh uh sarejo uh uh electrons okay they would be pulled by in different directions by four different atoms single bonds and because of that uh it's going to be i said because of that it's going to be tetrahedral and uh all the bond angles are going to be 109.5 like in benzene uh it is this is the the shape of carbon in benzene uh remember you get questions on this uh so this is how how carbon looks like in benzene okay carbon is bonded to three atoms eight electrons and the fourth electron no one is attracting it tk so that fourth electron unused p orbital it forms a pi bond so this is exactly what happens in benzene you might be asked to draw the structure or describe the structure of benzene look at each of the carbon atoms uh they're all making three single bonds so it's it's trigger uh it's a trigonal planar 120 degrees fahrenheit and there's one electron that's uh the p orbital that is unused initially that's the one that's uh that's involved in pi bonding so high carbon every carbon has one of these p orbitals and they start to overlap with each other and they end up forming this delocalized pi electron cloud and uh so this is the way cambridge expects you to represent benzene uh six carbon atoms it's a planar molecule hexagonal planar 120 degree angles and uh there's going to be a ring of pi electron cloud and all the reactions most of the reactions of benzene are going to be determined by this ring of pi electron cloud uh you have the skeleton formula or again bond energy patagonia data booklet this is how the carbon carbon bond in benzene would look like uh there's going to be a single bond plus there's going to be this delocalized electron cloud but a very partially localized electron cloud if you want to figure out the bond energy now the other thing about this is compared to alkenes alkenes have pretty much the same structure as well so here is an alkene molecule now alkene together you have two carbon atoms and they they're both sp2 hybridized there's a p orbital unused unused p orbital and they end up forming these pi bonds above and below now in the case of alkenes the pi electron cloud is uh has a high charge density because it's very concentrated uh it's all uh it's all concentrated in this middle area over here but in the case of benzene the pi electron cloud is more distributed because if you look at any of the p orbitals uh not only for example if you focus on this red p orbital not only is it overlapping with the carbon on the on the on the top but it's also overlapping with the carbon on the bottom as well so the electron cloud uh is it forms a delocalized electron cloud and the electron density is much lesser as pi electron cloud is distributed over a much wider area uh so the pi so the p orbitals are overlapping with the carbon on the right but they're also overlapping with the carbon on the left so the electrons are more distributed so remember there's a huge difference between the electron density of an alkene compared to a benzene so it's a huge difference now uh we're going to focus on alkenes first here very quickly uh uh what were the reactions of alkenes that you studied in as because that's going to come as i mean you're always going to get questions as comparisons uh with alkenes now alkenes known as unsaturated hydrocarbons uh so they attract electrophiles and alkenes have electrophilic addition reactions uh for example bromination over here when it comes to bromination uh the bromine molecule gets polarized by itself why because uh this double bond has a high electron density and has more polarizing power so the electrons are very concentrated in this in this tiny area over here so they repel the electrons over here uh this bromine becomes partial negative this other one becomes partial positive so the polarization happens on its own and the bromine molecule splits up the negative bromine is going to get repelled the positive bromine is going to get it's going to be attracted so the positive bromine is going to pull all the electrons from the double bond over here and it's going to take those electrons up uh gain those electrons this positive bromine so this carbon would become a carbocation it because the double bond over here the electrons over here have been taken over have been uh are now with bromine over here so in the next step the b minus one which had initially broken off which had initially repelled uh because of the formation of the carbocation it's going to get attracted to it and it would form this molecule over here so so remember alkenes they're going to polarize bromine on their own uh you don't need specific conditions for this it happens in the dark at room temperature then there's a thing called markovnikov's rule you must know which carbocations are stable and which ones are unstable for example if you have if you have an unsymmetric alkene now in an unsymmetric alkene uh the for example if you have an hbr molecule that's getting added in an unsymmetric alkene uh the h is going to go and pull the electrons over here now this h could bond with the with the carbon on the right side and the br could be on the left side or vice versa so two things could happen and let me explain that quickly so the h could bond with the carbon on the right and this carbon would become a carbocation and br negative in the next step would come in and it would get attracted to it or vice versa the h could pull these electrons and when it does that it would take these electrons bond with it the h positive charge would end this carbon would become a carbocation because the age took its electrons and the next step br minus one is going to come in and it's going to get attracted to the carbon on the right so the two possibilities of carbocations that are possible uh but which one is more stable uh remember it's always the carbocation that's bonded with more alkyl chains it's this one this is going to be your stable carbocation and the reason being that the reason it's stable is that alkyl chains have an electron donating effect so on both sides there's a ch3 group so they're going to donate electrons they have an electron to dating effect which is why the positive charge is going to be much lesser and if the positive charge is lesser then the small positive charge is going to allow the east to take your electrons because who was taking away electrons from it it was the h that was initially coming in uh so this carbocation forming this carbocation is a lot easier forming this particular carbocation is more difficult because it's bonded to hydrogens the more hydrogens there's only one carbon chain attached to this one so forming this carbocation is kind of more difficult because the positive charge is a lot greater so if the h was coming in and was trying to steal electrons it would not be able to steal the electrons if this is the carbocation that's formed because it has a higher positive charge and it would not allow the h to take electrons away from it so this is the unstable carbocation more difficult to form okay so remember this and you'll be asked this over and over again uh in a2 as well you'll be asked questions about carbocation stability remember the carbocation which has more alkyl chains that's more stable and that's the more likely one that's going to be formed as anyways you had uh in as you had these alkene reactions bromination hydrogenation in hydrogenation you had adsorption in d adsorption just quickly going over that you had hydration uh pretty much the same mechanism uh phosphoric acid catalyst 60 atmospheric pressure and 300 degree centigrade was the temperature then alkenes would also react with hydrogen halides like hbr and the double bond would go and http would get added to it and then you had a new explanation of alkenes yes it's your hydra which one hydration this is hydration it's phosphoric acid catalyst i'm going to show you the board link as well if you're trying to copy this now now phosphoric acid catalyzes 60 atmosphere pressure 300 degrees centigrade temperature so it's water in the form of steam and uh same thing happens the double bond goes and uh h and o h get added to it tk so did you also follow my channel margaret house rule is always going to be followed for unsymmetric alkenes take it you get there's going to be a major product there about hydrogen atoms tk if hbi is getting added to the double bond then the h would go with the carbon that's already bonded to more hydrogen atoms next is oxidation of alkenes remember there's my oxidation of alkenes which is cold dilute alkaline chemical what happens in mind oxidation then you have a double bond and it's like an addition reaction two oh groups get added to it uh so there's an oh group adding over here and over here uh on the carbons which was which were previously bought making a double bond uh so it is a molecule more complicated molecule double bonds uh so instead of the double bond you're going to have which getting added so that's so that's uh minor oxidation in strong oxidation you have three options the double bond is going to completely break and if the double bond breaks completely uh the molecule splits up and if the double bonded carbon atoms they had two hydrogens next to them then they would turn into carbon dioxide in h2o if there was only one h and one carbon chain then it would turn into a carboxylic acid and if the double bonded carbon atom is surrounded by two carbon chains then it would turn into a into a ketone so pasta you have these examples for example if you're trying to oxidize strong oxidation of this alkene it would break in the middle this carbon one carbon chain one h it would turn into a carboxylic acid so this is exactly what we did it turned into a carboxylic acid the rest of the molecule remains the same uh this carbon it has one hydrogen one carbon chain it would turn into a carboxylic acid as well uh similarly you can have a look at this one uh double bond would break this carbon would turn into a ketone why because two carbon chains uh this other one would turn into a carboxylic acid because there's only one carbon chain attached to it and there is one h so that turns into a carboxylic acid these are the other examples that are done so this is this is all about alkenes now we're going to move towards benzene now remember the major difference in an alkene in a benzene now starting here as the major difference as i've told you that the double bo the pi bond over here in an alkene uh it has very low electron density compared to an alkene so the first reaction is called an electrophilic substitution reaction what happens in an electrophilic substitution reaction is that bromine is going to be polarized in exactly the same way but the polarization is not going to be very strong because the electron density is not very high because this p orbital is not only overlapping with the with the carbon on the top but it's also overlapping with the carbon at the bottom which is why the electrons are more distributed uh which is why the electron density is not high enough polarization is weak so this positive charge is not very strong and if this positive charge is not very strong it's not going to attract the electrons from here it's i mean the attraction for electrons is going to be very very less and the repulsion of these electrons would also be very less so the bond is not really going to break uh because of the weak polarization so you need a catalyst you need a transition metal catalyst like febr3 or alcl3 or albr3 transition metals have a large number of protons which is why they have this tendency to attract electrons so they're going to pull electrons from the other side so benzene would be slightly pushing electrons but on the other side iron would be pulling electrons so the bond over here would get polarized and these electrons are going to get attracted and bond with fe as can be seen over here at the bottom uh the br is going to break and the br positive that's formed what it would do is that this br positive would go and would steal one of the p orbital electrons so you can see this is the carbonium ion that's formed because the br positive is going to take away the electrons from this particular p orbital which was previously overlapping with all the other p orbitals but now it's missing so remember one of the carbon atoms is now sp3 hybridized it's making four bonds whereas the rest are still part of the benzene structure so it's like it's so it's going to have a positive uh the big gene electron cloud is going to have a positive charge uh why it has a positive charge because uh pr took its electron and in the next step h gives the electron back so the h atom gives the electron back and h leaves h forms a positive ion that positive ion is going to take away the br from over here and it would form hpr and the benzene electron cloud would become complete again but as a result now you have a now you have a bromine substituted previously you had six hydrogens now you have one bromine in its place and the catalyst is regenerated so remember this mechanism uh the way you're going to write this mechanism in your exam is going to be this one this is the drawing that you're going to make uh it exactly explains the one that we just did above so bromine polarizing make sure you draw the curly arrows and the partial positive the partial negative charges clearly these are the intermediates so you have a carbonyl minus an intermediate and and these are your final products now the conditions for the reaction are you can do it with bromine so if you br through a brc are the catalysts or you can do it with chlorine so fcclc and lcl3 are your catalyst that's it so those are the conditions so next is nitration of benzene now nitration of benzene is uh you you have n86 hydrogens one of them gets substituted by energy it's the same mechanism uh the conditions are concentrated nitric acid and concentrates sulfuric acid the temperature is around 55 and n2 substitutes one of the each the mechanism of the reaction is you must remember the step one where the electrophile is created or produced uh so sulfuric acid and nitric acid react with each other and they produce so you have to remember this equation and when the no two plus one electrophile is produced it's going to go and it's going to just it's going to steal one of the p orbitals and so one of the carbon would become sp3 hybridized it's going to be making four bonds and the benzene electron cloud would have one electron missing because one of the p orbitals is gone so it's going to have a positive charge and in the next step the h would give its electrons and uh if you want to complete this that h would take electrons from hso4 minus one which was produced in the first reaction and h2so4 is going to be regenerated remember h2so4 is basically acting as a catalyst because the first step it helps to produce uh no2 plus one and in the next step in the h2so4 is region regenerated so this is the mechanism that you're going to write in your exam benzene benzene becomes positive it has a partial electron cloud now and h then gives its electron and bonds with hso4 -1 to form h2so4 next is you have hydrogenation of benzene now hydrogenation of benzene is uh just nickel plus h2 and 150 that would that the double bonds the pi electron cloud all of them they would become saturated single bond is like an additional reaction for an alkene and it would turn into a cycloalkane that's it uh then we're going to talk about derivative compounds of benzene yeah phenol which is benzene with no h phenylalamine with nh2 uh benzoic acid with carboxylic acid benzaldehyde and so on uh these are these are isotopes from benzene structures that are derivative structures phenols it's a different i mean this one is not benzene it's a different functional group tk so you you won't call it just benzene tk this is phenylamide when you have benzene with uh with a carbon chain highly benzene is known as benzene thicker so different groups attached to benzene now one thing you should remember is uh the groups that are two four six directing groups uh these are groups that have electron donating effect uh the oh nh2 and alkyl chains i mean ch3 has an electron rating effect which is why the electron density would increase on position two and six and also in position number four because all the rest of the electrons are going to get repelled and they would accumulate at position number number four uh so so you have two four six positions which have high electron density and uh because of that the electrophile geometry reactions particularly the electrophiles whether it's no two plus one or br plus one or c l plus one they're going to be attracted to position two four and six so for example if you're doing electrophilic substitution of addings foreign foreign [Music] [Music] foreign okay [Music] same mechanism everything is the same uh but now what would happen is bromine would either get attached to position number two because the electron density would be higher over there or it would get attached to position number four so and similarly uh nitration can that bromine would no two would get attached to position number two or position number four uh so two four six directing groups i said if if benzene has multiple alkyl chains what would happen then okay perspective for example i get up uh the two alkyl chains so according to this perspective two four six positions are uh this one there this is this this is going to be two this is going to be four and this is going to be six so inside positions for attachments like that according to this two four six positions are two is this four is this and six is this it's the same positions the two four six positions are two four and six orange one according to the green methyl group the two four six positions are two four and six so all of them are active all of them are active all of them have high electron density uh so the so the electrophile would get attached to any position whatsoever funeral same 246 directing groups but the thing is that in phenols you have a lone pair on oxygen which overlaps with benzene by electron cloud so you have lone pairs that are overlapping with the genes by electron cloud and because of that the electron density becomes very very high significantly increases electron density and because it significantly increases this is known as a highly activated benzene uh the reactions are going to be very very vigorous the same thing happens with nh2 n has a lone pair the lone pair overlaps with benzene so the electron density on benzene significantly increases so electrophilic substitution becomes a lot easier as benzene becomes activated and because you have high electron density so reaction is the action character no catalyst is needed all the polarization can happen with the benzene electron cloud because the electron cloud is very very uh it has a very high density the bromine or bromine surface you get a white precipitate of 2 4 6 tri bromo phenol uh but it's actually gonna you use it as a test for identifying phenols uh because the bromine gets decolorized and you get a white precipitate of 246 tribromophenol and the same happens with chlorine pin nitration of phenols concentrated nitric acid or concentrated sulfuric acid what all three positions it would get attached to that's the next one then you have the opposite versus three five directing groups which is deactivating groups draw electrons if they withdraw electrons the electron density on benzene becomes lesser and it and it actually becomes more it decreases more on two four six positions or relatively three five positions uh the electron density is kind of higher but overall electron c is lesser which is why the reactions are going to happen are not going to happen in the first place and if they happen then bromine would get attached to either position number three or position number five so so remember uh data booklet together three five directing groups are given like no2 uh like uh aldehydes like carboxylic acids these are groups when they are attached to benzene they are electron withdrawing groups and then we can move to alkylation now alkylation is you have uh you take a halogenoalkane a hydrogen alkane you don't need to know the mechanism and halogenoalkane the carbon is partial positive and the cl is partially negative so the partial positive carbon attracts the benzene but over here you need a catalyst like alcl3 now alcl3 would play the same role that the al because of its high charge density which is plus three it would attract the electrons from the other side so it would help in pulling away the electrons from of cl and pulling the cl atom away from this carbon so that this carbon goes and bonds with the benzene so you you have an alkyl chain that gets attached to benzene uh similarly uh so whenever you want to attach an alkyl chain to benzene you do uh alkylation and this is known as friedel crafts alkylation the other one is acceleration acceleration is uh you have a acelfloyd uh assets right again serial bondo and cls the carbon is partial positive you need a catalyst alcl3 which which pulls the electrons away the carbon i said the carbon positive is going to pull the electrons uh from the benzene the carbon with the double bond o is the one that's going to get attached to the benzene and hcl is produced as a result so remember alkylation and acceleration elcl3 is the catalyst uh now the other thing is okay i said these are all the reactions so far just in summary now oxidation of arrhenes uh whenever you have an alkyl chain attached to a benzene uh you add camino for acidified it could be alkaline as well uh reflux you get benzoic acid no matter what the alkyl chain is every time you're going to get a benzoic acid this carbon would turn into carboxylic acid this one would also turn into a carboxylic acid so that's oxidation of arenes we can do comparison of hydrolysis i said what happens in comparison of hydrolysis okay you have three chlorine related compounds benzene alakam khatta morgan he can be done with electrophilic substitution of benzene uh now we're going to do some other uh unrelated topics related to benzene but still slightly different comparison of hydrolysis so you've got three chlorine related compounds that you've studied you've studied uh chlorobenzene you've studied uh halogenoalkanes and you've studied acetylcholines serial bondo and cl uh so you have to compare okay cl hydrolysis is the reaction with oh ions or with water the first one has no hydrolysis uh no reaction with water the second one has some has has a moderate hydrolysis reaction it reacts with naoh aqueous and reflux and the third one has a vigorous reaction rapid reaction with cold water gives off fumes of hcl so this one is pretty strong hydrolysis so we you need to know what the reasons of these hydrolysis reactions are starting with chlorobenzene no hydrolysis why is there no hydrolysis the reason is water is a nucleophile it has lone pairs it gets attracted to a positive thing said it's attracted to to positive charge that's what a nucleophile is uh because it has load base but chlorobenzene has no positive charge uh because it has a pi electron cloud so that's a lot of electrons plus chlorine has a lot of lone pairs and those lone pairs are going to overlap with the with the pi electron cloud from benzene and they that would increase the electron density over here so there's a lot of electrons over here and because there's so many electrons uh the electrons over here are going to repel the electrons in the water molecule which is why uh there's absolutely no attraction which is why they're gonna they're going to repel each other so lone pairs on cl overlap with benzene pi electron cloud which increases the strength of the ccl bond uh so this bond over here kind of strengthens and it repels the water molecules halogenoalkanes now when it comes to halogenoalkanes uh in as you have studied sn1 and sn2 reactions so sn1 is for tertiary halogenoalkanes and sn2 is for primary halogenoalkanes uh so you had if you know in as you have studied three nucleophilic substitution reactions o h minus one there was a there was one with c n minus one and there was one with nh3 uh in all three cases the nucleophile attacks if it's a primary halogenoalkane the nucleophile attacks the carbon positive center uh the ccl bond is polar and this carbon has a very strong partial positive charge because it's pointed to fewer alkyl chains so alkyl chains have electron dating effect or which is why since there is just one of them the positive charge is relatively strong and it attracts the oh minus one the os minus one gets attracted to it and the cl gets repelled and as a result uh that's a transition state and in the next step the cl minus one breaks off now in sn1 what happens is what happens is that the carbon positive is not very strong because it's surrounded by three alkyl chains and they all have electron dating effect uh as so so that results the nucleophile is not going to be attracted this one second alkane the positive is not very strong which is why initially the o h minus 1 is not attracted so in the first step the c minus 1 breaks off on its own and the reason it can break off is because the positive charge is very weak and it's not going to attract the negative cl so the cl would easily break off and you get a very stable carbocation because it's surrounded by carbon chains the positive charge is relatively lesser so it allows the cl minus one to break off and you get a stable carbocation in the next step oh minus one comes in and bonds with this so remember sn1 and sn2 mechanisms now now we're going to come to asylum rights which is stronger hydrolysis now this is one reaction and one mechanism that you have to remember and this one is a new one you don't get this often in your in your past papers as well but uh i mean from now on it's it's going to be a very important mechanism in a2 chemistry so you have i mean most people forget to learn this remember this just this was just added one or two years ago so you don't see this in the past paper but you can get this mechanism now acetyl threads have a very strong carbon which is uh which has a very strong partial positive charge which is why it has a very vigorous reaction so positive carbon in rcocl is bonded to two highly electronegative elements so it has a strong partial positive charge density and it attracts nucleophiles very strongly so it's going to attract the water molecule very very strongly and if it attracts the water molecule strongly uh water with its lone pairs it's going to donate its lone pairs to this positive carbon atom and the double bond over here which you can see over here because of the lone pairs coming in these electrons over here are going to going to be repelled so you're going to get an o minus one charge on top and the water molecule will have a positive charge because it lost its lone pair to this carbon atom next step in the lone pairs come back they form the double bond which is reformed and the cl breaks off so the cl minus one has broken off and then the cl minus one comes in and pulls away one of the h so the h gives the electron and the auxin lone pairs are reformed and that results in the formation of a carboxylic acid so so this is what's happening remember this mechanism uh carbon strongly positive in an acetylene water lone pairs get attracted to it double bond electrons they get repelled so you get o minus one on top and you have a water molecule attached to it to the bottom uh the electrons that were pushed away they get attracted back to form the double bond which you can see over here and the cl because these electrons are coming in these electrons the cl electrons they get repelled and the cl minus one breaks off and while leaving the cl minus one pulls away one of the each as well so one of the h over here is going to be pulled by the cl and oh would be left over here so the carboxylic acid would be found so vigorous hydrolysis remember the reason for the vigorous hydrolysis because you have a very very strong positive carbon atom now next one another thing that you have to remember is the comparison of acids now comparison of acids is uh you have to compare four acids you have to compare alcohols water what is just there as a reference uh you you have phenols and you have carboxylic acids now carboxylic acids are obviously the strongest acids uh phenols are kind of in the middle and alcohols are weakest acid they all have o-h groups white over here which over here and o-h and carboxylic acid they all dissociate but alcohols are the weakest they have the weakest dissociation why because uh we're gonna we're gonna understand the why uh but remember alcohols are extremely weak acids they ionize even less compared to water so the first one is why are alcohols weak acids now the reason alcohols and just let me i said so the reason alcohols are weak acids that alcohols have an alkyl chain attached to them so when when the o h dissociates and h plus one ions are formed and o minus one is formed the alkyl chain has an electron donating effect and because of the electron rating effect the negative charge density increases and if the negative charge density increases it would immediately pull the h plus one back and would not allow it to dissociate so that is what's happening so alkyl chain has this is what you're going to write alkyl chain has electron donating effect which increases charge density on the cst ch2 over minus 19 which makes it very unstable because it has a very strong negative charge density and it would immediately attract the h plus one back again hence it retracts the ace person back and doesn't ionize so less dissociation very less dissociation in the case of alcohols now with now alcohols only have one reaction which is with the very reactive metals group one metals like sodium and it's like a metal plus acid reaction where uh sodium methoxide is formed if it's ethanol uh the h would get displaced and it performed it would form h2 gas uh but it's a very slow reaction and that's that's about it now phenols what's happening in phenols phenols are kind of relatively stronger acids compared to alcohols why because the lone pair when the h leaves and the o minus one is formed the lone pairs over here they start overlapping with benzene benzene electron cloud they mix up with the benzene electron cloud and when that happens the lone pair or the negative charge density over here decreases so lone pair on benzene overlap with benzene's pi electron cloud which decreases charge density on the c6 h5 or minus 1 iron uh so lesser attraction for each plus one so it's going to allow the each person to go to leave because the negative charge is not going to be very concentrated it won't have a very high charge density so it would allow the h plus one to break off phenols are kind of stronger acid so phenols not only have reactions with metals but they also have reaction with bases they don't have reactions with carbonates which are weak bases so apart from the reactions with carbonates phenols can react with bases any which a salt would be formed which in this case would be sodium phenoxide uh in both in the first case with a metal it's going to produce hydrogen gas and with a base it would produce a water molecule tk i suffered carboxylic acids why are carboxylic acids such strong acids so because the reason is that when the h plus one leaves the o minus one charge the negative charge over here it gets pulled or attracted by the other auxin because there's another auxin right next door so there's a highly electronegative auxin atom right next door and that oxygen atom attracts it attracts the lone pair so the electrons they get distributed between the two oxygen atoms so oxidant c double bond o has an electron withdrawing effect which decreases charge density on the ch3co minus 1 iron so the negative charge is not very very concentrated and that makes it stable and there's going to be less attraction for h plus one ions so carboxylic acids dissociate more and they have all acid reactions which can be seen over here they can be they can react with metals like calcium to form calcium ethanoid uh they can react with bases for example no h plus methylic acid uh the oh would be lost and na plus one would take its place to form sodium methylate uh they can react with carbonates as well to form salt water and carbon dioxide and they can also react with ammonia so they can have all acid reactions tk so the summary is that what's a strong acid a strong acid is any asset that has a has a lot of electron withdrawing groups attached next to the uh and vice versa because if you have electron withdrawing groups attached next to the oh like over here the electron withdrawing groups are going to pull the negative charge density away from the o minus one which is why the negative charge density is going to be lesser and the ace plus one is not going to be attracted to the negative charge so that's the summary if you have more electron withdrawing groups so you can have comp you can now we can do more comparisons like this based on this comparison of strengths of alcohols as acids so for example you have three alcohols uh now the alcohol if you're trying to compare these two this one has a bigger alkaline chain so more electron donating effect so the negative charge is going to be very strong which is why it's going to attract these person very strongly and it would not dissociate or would not let the h plus one go away uh similarly if you can add a withdrawing group like cl you can add a cl uh the cl is going to withdraw the electrons because because it's electronegative and that would decrease the negative charge on uh on o uh and which is why the ace plus one can can be allowed to leave it won't dissociate so remember if you have more alkyl chains or you have bigger alkyl chains it's going to form a weaker acid um so you can see a phenol over here a phenol with alkyl chains that's going to be a weaker acid compared to a normal phenol because these alkyl chains are going to push electron density and the electron density over here would increase so it would attract these person back again instead of letting it go instead of dissociating remember would be the acid uh similarly you can have electron withdrawing groups uh so for example if you have cl uh the cl is going to withdraw electrons and the negative charge over here would become lesser and it would become a stronger acid because it would dissociate more it would not attract h plus one ions so that's the summary electron donating groups close to it that's a weaker acid electron withdrawing growth close to which that would result in a stronger stronger acid yield summary reaction scheme remember alcohols only react with na phenols react with nan naoh carboxylic acids react with nanoh and n2 co3 all of them now similarly you can compare do a comparison of bases basis is going to be exactly the opposite now all bases are nitrogen compounds uh you have amites you have phenylamine you have ammonia you have alkylamine this is the most basic this is the least basic everything depends on this lone pair over here okay uh for example alkyl mines why are alkali mines the strongest bases why because they have an electron donating carbon chain electron density on the lone pair increases so it would attract the ace plus one very strongly uh so if you have if you have more alkyl chains like over here you have more alkyl chains or more electron rating groups it's going to be a stronger base i said what about phenylamide in phenol mine what happens is that the lone pair mixes or overlaps with the pi electron cloud on benzene so the lone pair is not really available or its charge density is very less so it would not attract h one that strongly so it's a weak base uh the attraction for s plus one is going to be much lesser as amites on the other hand they are not basic at all why because the lone pairs go completely missing you have a very highly electronegative auction which pulls the lone pairs and the lone pairs they eventually end up mixing with the double bond over here so they're simply not there uh and so there wouldn't be any attraction for each plus one so highly electronic negative oxygen withdraws lone pair and lone pairs they start to overlap with the pi electron cloud in serial bond o and they're simply not available to attract h plus or nine so if there's an h person roaming around it would not get attracted to the lone pair over here because i said so it won't get attracted to the loan pay and uh because the loan pair is not there tk the loan is completely pulled to and mixes with the double bond over here so this is alkyl chain alkyl uh so this is a composite of bases nitrogen bases now we're going to move to organic nitrogen compounds uh so starting with how do you form these nitrogen compounds for example if you want to form an alkaline what you do is uh you take a nitrile and you reduce it how do you reduce it you have lil h4 that's a reducing agent or you could use nickel plus h2 so these are your reducing agents you can reduce them and the triple bond would go and hydrogens would get added and it would form an amine similarly phenylalamine what you could do is you can take a nitrobenzene and you can reduce it with tin plus concentrated hcl uh if you do that the o would be gone and the h would take its place uh so that's that's your reduction here just a second if if i'm missing something need that's it now acetolates the formation of acid rates uh isochlorides are formed when you have a carboxic acid and you reacted with pcl5 or pcl3 plus heat or so cl2 plus heat and that results in the formation of acetoid that the oh would be gone and the cl would take its place that's a pilchar reaction and you have reactions with esters or ester formation uh ester is this group serial bond one o in the middle of the chain carboxylic acid and alcohols they combine to form ester and water molecules uh to form them the conditions are concentrated sulfuric acid and reflux it's a condensation reaction and you can break the ester down by heating your diet with dilute acid or dilute alkali and reflux so both ways you can form it and you can break it's the reversible reaction so how do you how do you form esters uh the first thing is you must know how to draw the structural formula so you've got a carboxylic acid like over here you have a propanoic acid and you have a you have a pro an ethanol molecule now remember why is in ester forming because the oxygen lone pairs it gets strongly attracted to the double bond o carbon which is partial positive so there's strong attraction between the two and the h and o s they get repelled and they end up forming water molecules so you're going to remove the h and oh in the middle and you're going to link them up and how do you name esters s's are named in two parts one side is eth two carbon atoms the other side is prop three carbon atoms so f and prop the singular side is called while so it's going to be called ethyl and the double bond oversight is going to be called uh 08 propanoate so that's how you're going to name them so so a bunch of esters remember the functional groups have to be drawn in front of each other so that over here you have a propane to all molecule and you have a butanoic acid so the o h and h are lost and the two are going to link up at this point the gas can be shown over here that's now hydrolysis of esters uh you can break it up uh if you have an ester just break it turn this into carboxylic acid turn this back into into an alcohol so and also remember in alkaline hydrolysis you always get a salt of carboxylic acid not the carboxylic acid because the carboxylic acid formed it ends up reacting with the alkali i said uh now acetylides are very good at forming esters as well uh if you bring in an acetyl chloride the carbon is positive and the o is has lone pairs the carbon is more positive in this case so the reaction is a lot more vigorous and you get the ester in the same way but instead you have an hcl molecule that's being produced now also remember academics as well as amides women this is a polyamide i'm going to just quickly do amites first also remember acetoids are used to make amides uh so you have an asteroid with a positive carbon atom and you have a lone pair on in and they get attracted and the end result is you get enemite is formed so i said now phenols coming back to ss remember phenols they only make esters they don't if you have a phenol which is like an alcohol but not exactly like an alcohol and you have a carboxylic acid carboxylic acid are not going to react with phenols the reason being that the lone pair is not available or its electron density is very low so it's not going to get attracted to the carbon that is positive so instead what happens is there's a positive carbon atom uh you need an acetylene because the positive carbon atom is stronger and because it's stronger the lone pairs are going to get attracted to this particular carbon atom and you need alkaline conditions you need naoh for this so remember phenols they will only make esters with with acid chlorides as a coming to azodize uh remember azure eyes are very very stable colored dyes used in paints so you've got you've got a phenylemine that's the first thing that's the first raw material that's used and uh nno2 and hcl is used temperatures kept less than 10 and you get a very unstable ion which is known as a dysonium ion n triple bond n plus one also written as h5 n2 plus sometimes cl minus 1 is written next to it now it's a very unstable line remember that and it has to be kept below 10 degrees centigrade it decomposes very quickly if you if you add water and the temperature increases above 10 it quickly decomposes to form to form a phenol now what's the purpose of the digenemine that does only mine reacts with an activated benzene so you need an activated benzene it it either has to be a phenol or a phenylamide so it's either going to have oh or nh2 why do you call it actuated because the lone pairs on os or nh2 are going to mix with benzene electron cloud and the electron density would be higher and if the electron density is higher there's going to be more attraction for the n triple one n plus one so these two are going to get attracted and they would form this azo group which is n double bond in in the middle um and you need alkene conditions for this any which is used so that that will result in the formation of an azo dye so always remember you form a diazoni mine and then you react it with an accurate benzene so this is how you figure out uh the reagents for azotize uh this is the azo group if you want to find out the region uh remember the entrepreneur n plus one was with the with the benzene that was inactive uh so you would be asked to identify the reagents or the reactants for azuritized or formation of azurites so remember that uh if you want to go in the reverse and you want to find the reagents it's going to be a diagonal mine and a phenol or an or a phenylamide but you have to break it at this point why because this is the accurate benzene the n triple bond n plus one came from the other benzene so n one n plus one goes to this carbon atom or this benzene so let's move to polymerization now first one polyesters uh polyesters are made from diodes and dicarboxylic acids or you can use diesel droids so h and os are lost asian whites are lost aceno h are lost and that results in the formation of an ester link the which is lost and the ace is lost and they would join up to form an ester link now examples are uh like you have you have a diol uh for example over here you have ethane one two diode and you had a carboxylic acid the oh was lost here and the h was lost and it kept on happening and as a result you've got you got this long chain hydrocarbon now there were some comments about the properties of polymers like crosslinking and branching so remember polymer chains are all entangled together like at the microscopic level uh these tiny strands are all linked up like for example your hair is a polymer so it's basically lots of tiny tiny strands very microscopic nanostrands all entangled with each other now if the chain is non-polar then it's going to have van der waals forces and uh it would be relatively weak or soft so you have a lot of polymers like plastic packs that can be stretched easily reason being that the chains can easily slide off that's why they can be easily stretched out so they the chains can sort of come out or they can get disentangled very easily because they're not attracting each other but if the chains are polar then it's going to be a strong polymer you would not be able to like your hair is very strong it's very hard to actually stretch it so you've got polar chains polar chains uh that have dipoles in them they're going to be very strong because the chains would be attracting each other very very strongly now hydrogen bonds is the one that's the strongest so so if the chain or the strand is making hydrogen bonds then then it would be very very strong but at the same time it would also be water attracting like sponges tk sponges for dish cleaning they're all water interacting uh your nappy baby nappies they're all water attracting so if you have a lot of o-h groups in a in a chain then it's going to be it's going to be attracting water very very strongly so remember how the properties would be affected by having non-polar or polar chains here are their side chains side chains can affect the way your polymer polymer behaves because if a polymer has a lot of side chains or branching then the branches can get stuck with each other and the entanglement would be much much harder so if you if you have more branches then the polymer chain would be more entangled and the strands would be more entangled with each other which would result in a stronger polymer then there's a thing called cross-linking which is that two chains can sort of join up like for example they can form an ionic bond like you had a carboxylic acid and you had an amine on the other side what could happen is that the carboxylic acid would lose its plus one and the amine would gain an h plus one and they would end up forming an ionic bond or there's a carboxylic acid on one side and alcohol on the other side and they could join up and to form to form an ester link so all sorts of cross-linking is possible different groups on one chain can bond with different groups on the other chains yes or no yes sir conducting we also think if you have alternating double bonds like double bond another double bond another double bond in the chain what would happen is that all the double bonds can mix up like the red ones overlapping the red ones over here are overlapping so why don't they start overlapping with each other so you get a delocalized electron cloud and that results in a conducting formation of a conducting polymer now polyamides are now what happens in polyamides you have you've got amino acids which are given in your data booklet amino acids have this tendency to form vitamins which is that they're capable of accepting gastroesolines because they have an acidic group at the same time they have a basic they have an acidic group at the same time they have a basic group as well that is that the base can accept each person and the acid could let go of these blossom lines so zwitterion is something that's formed when both things happen the acid loses h one and the base gains h plus one i said so that's his veterinarian it's it's an iron it's a molecule having no overall charge but has regions of positive and negative charges there's a thing called isoelectric point because i told you that uh it's not necessarily that the carboxylic acid wants to lose its h plus one uh so for example the nh2 and the carboxylic acid they might have different strengths like this one is a strong base so it would accept ace person very very strongly but this one is a weak acid it's not letting go of the ace plus anions so what can happen is that you can increase the quantity of oh science you can make the solution basic if you make the solution basic the carboxylic acid would be forced to lose its aspersonines so so this vitamin is formed in a basic environment tk so it depends it varies from different amino acids to different amino acids every each one has a different isoelectric point at which it is written in a glyphosate uh in proteins you have a you have the primary structure which is the amino acids all so all these amino acids that are given in the data booklet so they're given in the data booklet and they can be uh copied from there amino acids are written by the three-letter abbreviation which is lys for lysine vl for valine they link up the h and o h are removed and you get mi linkages in the middle second structure is once the initial strand is made the strand could coil up in a sheet like structure that's called a beta pleated sheet or it could coil up in a in a spring-like structure known as a alpha helix um why do they coil up because every every amide has hydrogen bonding because there's a cedar bondo and nh group in the strand and this o lone pairs can get attracted to the h positive from the lowest strand which results in strong hydrogen bonds and which is why which is why you get this coiling uh the positive and the negative they attract each other which is why you get this coiling in the first place i said then you have the tertiary structure then once you have the primary secondary structure the r groups can interact with each other every amino acid has these groups that are attached to it so aspartic acid has carboxylic acid lysine has nh2 they can react together to form deformatic bonds so all sorts of interactions are possible in this uh in this tertiary stage so iodic bonds covalent bonds hydrogen bonds van der waals forces every type of attraction is possible so our group of one molecule can get attracted to the r group of the other molecules so at the end of the day this is how the molecule would look like that would be strands coiled up alpha helix bw sheets uh and those pw cheese are again further coiled up and the r groups are interacting with each other tk so that's it up here you have addition polymers which is uh alkenes and you have oxidation of carboxylic acids two of them you must know that carboxylic acid is methanoic acid gets oxidized by tolerance of fillings and you have ethane dioic acid or oxalic acid that gets oxidized by chemonophore so oxidation of carboxylic acids just two of them the list is mostly yes [Music] foreign i said no boardings devices love this