[Music] in this video we're going to be looking at topic 10 C of the organic chemistry for a s we are looking at alcohols which is part of the hollow general alkanes alcohols and spectra topic so the learning outcomes that we're going to be covering are the nomenclature and how to draw alcohols being able to classify them as primary secondary tertiary looking at specific reactions of alcohols including how to halogen ate them and also how to oxidize them and looking at the techniques of how to prepare a purify and a liquid organic compound and then we'll do some past favorite questions at the end so alcohols are homologous series with the general formula cnh2n plus 1 or H so of course they are not hydrocarbons because we have this hydroxyl group that is being attached to it the formula can sometimes be simplified to R or H where R as any I'll count it for example efile or profile and the O H of course being our hydroxyl group the way that we named these as very similar to our branched alkanes alkenes and our halogen or alkanes the one thing that we must ensure that we do is we identify the location of the hydroxyl group because we can get structural isomers as we can see here that we can have pro pan tool but we can also have pro pan one all and as we'll see as we go through this topic these two things can have different reactions so it's very important that we understand that if we have more than one alcohol group then we use our prefixes so die o with mean two and try o with mean 3 you really have any more than 3 that could possibly come up so we can classify alcohols as primary secondary or tertiary depending on the number of our characters that are attached this is exactly the same with we classify halogen or alkanes so if you've watched that video then you'll remember that we classify primary as if they have one I'll tell grip r1 iron grip attached secondary will have two bar grips attached and tertiary will have three argue loops being attached to the carbon that contains the all H it is very important that we can classify all of our alcohols because as we've said they do react and very different ways so there are four reactions of alcohols that you must be able to identify and these are combustion conversion - hello gional alkanes dehydration to alkenes and oxidation good thing as you are not required to know the mechanisms of these reactions some of these mechanisms may come up when you go into e2 but we don't need to worry about them at a s level so if we start off with the combustion where alcohols as we already know are very very flammable so they can undergo complete combustion with oxygen and similar to the hydrocarbons they are going to form carbon dioxide and water we've actually discussed this already back in topic 4 when we discussed biofuels please make sure that you are able to rate out the complete combustion of F of alcohols such as ethanol so you're gonna have your alkyl group with your which reacting with your oxygen to form your carbon dioxide and your water this can easily be a one or too much question and an exam we can convert our alcohols than to halogen or alkenes and this involves the replacing this hydroxyl group so roh with a halogen and that halogen could be flirting coating bromine or iodine now we are only gonna focus on coding bromine or iodine and the we call these halogenation reactions that each halogen requires a different methods and different reagents you must be able to name all of the conditions and all of the reagents required for each of the reactions so let's start off with coordination there are two different coordinations that we have to know if we have a primary or a secondary alcohol such as propane 100 or propound - then we have to read to the alcohol with phosphorus 5 cordite at room temperature which is less pcl5 here and you can see that we're gonna make our halogen allow Kim plus pocl3 and HCl F as a tertiary alcohol such as the one shown here we will react it with concentrated hydrochloric acid at room temperature can we form a tertiary halogen or alkyne and water as well for illumination the regions are a mixture of potassium bromide and 50% concentrated sulfuric acid and we have to warm this mixture as well so we have two different parts that are reacting and we can then form our HBR so we have our KBR reacting with our sulfuric acid depending on what really takes it doesn't matter and we make our hbr which then reacts with the alcohol to form our brawn our alkyl bromide for i ordination the regions are a mixture of red phosphorus and iodine which are heated under reflux so we have our phosphorus in our iodine forming that's pi/3 + pi/3 then reacts with our alcohol and we form our aldol alkene please make sure that you can write the equations for each of these and you may wish to add these to your organic map to show all of your reactions and check on the YouTube channel for a video to show you how to do that so dehydration's to alkenes as another reaction that we have to know and we do this by hitting the alcohol with concentrated phosphoric acid h3po4 this is very similar to a halogen or an elimination reaction that we've seen in the halogen or alkanes because it removes the o h plus an adjacent hydrogen atom and we will form a double bond now we can have two possible products forming we can have Beauty one in our Beauty to yin just depending on where which say the hydrogen comes from so if I just draw it this molecule we have ch3cho itch ch2 ch3 so this has butan to all so of course we're going to remove this or itch after we remove the O H here on the right hand side we are going to form a butte to in and if we remove the itch from the left hand side we're going to form Butte one in so just be aware that you can have major and minor products but you're not required to go into a lot of detail about these one of the most important parts of this topic is the oxidation of alcohols and s is something that will come up and unit 2 unit 3 as it is also a core practical and you will also come back to it and units 4 & 5 when you get to e2 as well so the oxidation of an alcohol molecule involves the loss of a hydrogen that is attached to a carbon atom and the hydrogen atom that is on the OHA OOP so we have this o H and this hydrogen being lost and we're forming this carbonyl group here so it's very important that we can distinguish between the this is our hydroxyl and this there's a carbonyl group the C double bonded to an O notation it alcohols cannot be oxidized because they don't have this hydrogen atom on the the carbon of the co each group so you can see here that this is actually have our Carroll group so these do not undergo oxidation so we're only going to be focusing on primary and secondary in terms of oxidation so if we start with secondary secondary alcohols can be oxidized to an organic product that is known as a ketone and they have this general formula our C or R and that just means we have any alkyl group a carbonyl and then any alkyl group so the carbonyl group appears and the middle of the chin so an example of this would be propound to are going to throw pan on so propanone being our ketone then we can see that it's a ketone because it ends and this or any and this is the formula or we would have ch3 the carbonyl group and a ch3 and we're gonna form water here know the oxidizing agents you can see is simply written as all M brackets that is because we don't need to know much about the actual oxidizing agents themselves other than the fact that they pervade oxygen so the oxidizing agent that can be used as acidified potassium dichromate and when we get their secondary alcohol going to the ketone we see a color change from orange to green that tells us that an oxidation has taken place primary alcohols are slightly different because they can be oxidized and to different stages so the first stage is to form an aldehyde which has this general formula r2c h o and the second stage is to form a carboxylic acid which is our G or H so if we look at an example of this well we've got proton one of our plane minute reacting with our oxidizing agent and we're going to form this for Pinal so propanol is going to be drawn out as ch3 ch2 C double bonded to the or plus a hydrogen this can then be further oxidized in order to form our propanoic acid then if we write our propanoic acid we have CH 3 CH term C Oh or each and we've got the genital equation down here so we have our primary alcohol reacting with our oxidizing agent to form an aldehyde which can then be further oxidized to form a carboxylic acid so this is a nice summary of each of them and you can see that going forward that is going to be our oxidizing so when we have this or it means the oxidizing agent now you can reverse these reactions and that is what the inches and this is a reducing agent but you do not need to know much about the reducing reaction or the reduction reaction so that is something that is going to be discussed later on and the level usually an e2 so just to go through again we have our primary alcohol being oxidized to an aldehyde which is then further oxidized to a carboxylic acid a secondary alcohol being oxidized to a ketone and has then not toxa dyes any further and a tear shooting alcohol cannot be oxidized at all we can carry out chemical tests and I just to look at these alcohols to see what has been oxidized and what and if we can identify them so there are three different ways that we can look at and these come up and the analysis of unknown substances for practical so please feel free to check that video out as well the first test that we can do is we can warm it with acidified potassium dichromate and we get a color change from an orange to green this tells us that we either have a primary or secondary alcohol because an oxidation is taking place or we have an aldehyde going to a carboxylic acid alternatively we can heat with feelings or Benedict's solution and we get a red precipitate being formed and this is a test for an aldehyde if you have a ketone you will see no color change and we can also react it with tollens reagent and we form a silver matter and again that tells us that we have an aldehyde and if we have a ketone we get no color change we can do a number of different tests to see if we have carbonyls but again we'll revisit and I ate oh these are the three tests that you have to know so if we have potassium dichromate with a color change it's either a primary or a secondary alcohol or an aldehyde or the feelings or the tolerance will give you a positive test for an aldehyde now if we focus on the oxidation of primary alcohols we also have to take into account the fact that there are two methods of prepetition depending on how much oxidation we want after we want fill oxidation and we want to make our carboxylic acid we are going to use best methods which is known as heating under reflux if we want partial oxidation where we're going to form our aldehyde then we're going to use this method which is destination weapon you need to be able to sketch these and label them because it does come up and in an exam and both unit 2 and unity so let's go into just a little bit more detail about each of them so hitting under reflux is when we want to make a carbon carboxylic acid now the alcohol and the oxidizing agent which I'm going to be in a reaction mixture are very volatile because we're going to be heating here when we heat this and they're volatile they're going to escape and of course being able to start to rise up the condenser now the condenser here is going to be wrapped around this chip and the center and it is going to have cold water being put in does collect the vapors and it turns them back into liquids and it actually causes them to go back down into the heating flask so the vapors do not escape and we keep everything in the flask until the oxidation is really carried out we can also add something called anti bumping granules and that just makes sure that we get a nice smooth boiling and we get boiling all the way through our entire mixture if we have the desolation with a dashing setup then we use this in order to detect to get an aldehyde so again we're gonna have to have some heat and what we do is we heat the oxidized make sure so this would be your potassium dichromate or whichever oxidizing agent you wish to use and we slowly add the alcohol from this funnel here and you can see that it can drop through down into the oxidizing mixture now as the aldehyde forms it has got a much lower boiling point than the alcohol that is used to make it so the aldehydes boiling point there's slower than the alcohol boiling point so what that means is it's going to automatically turn into a vapor it is going to pass through the condenser here time into a liquid and be collected and this flask and the receiver and this is your aldehyde mixture and include it the only thing you should have left and your oxidizing mixture because your any oxidizing agent that's left over and any alcohol that has not reacted now when we make any sort of organic liquid we always have to purify it because we want to make sure that we are getting rid of any impurities and we have a pure product so it's not going to have any sort of issues if we want to use it in the pharmaceutical industry or for various different reasons so we use different methods in order to separate and intend the product from a reaction mixture and depending on whether the intended mixture as a gas a liquid or a solid will determine what different techniques that we use now you've met some of these before and these were again come back up and topic 20 of organic synthesis at nature and that will can go into more detail there but let's cover the key ones that we have to know now so simple distillation you met back in GCSE this is to obtain a liquid product that has a lower boiling point than others and the reaction mixture and it should be by at least 25 degrees Celsius so F for example we had a mixture of ethanol and water ethanol has a boiling point of 78 and water has a boiling point of 100 so we can actually separate out the ethanol from the water using distillation where we simply heat the reaction mixture and the vapor is pass through the condenser and are collected and to a flask and as long as the temperature remains steady that means that we're making the same product during our destination if the temperature changes and we see a spike then we're making a new product and we would have to then change out our REM bottom flask we can also use fractional distillation where you have seen fractional distillation and a larger scale when you've been talking about separating crude oil but we can do it in our laboratory and are very much of a smaller scale most of it is very similar to simple distillation the addition that we have though as this fractionating column which is this column right here which is filled with glass beads or broken glass now these act as surfaces in order for the vapor to condense and be reevaluated as more hot vapor passes through the column and what that basically does is it allows for better separation so we get constant condensing and evaporation happening within the column and the more it condenses and the more it evaporates the better it is going to be to separate and then by the time the vapors get up to the condenser again they pass through and they go into the round bottom flask to be collected now if we have an organic product where we want to remove using a solvent or we can do this thing called solvent extraction where we use a separating funnel and again that comes up and the core practicals so the solvent that we want the to mix with our substances should be immiscible with the solvent containing the product okay and the desired product should be more soluble and the added solvent so basically what we'll have is we'll have a liquid that contains our desired product we're going to add on a solvent that will allow us to take the liquid from the initial and go into this a new one and what happens is we place unto the separating funnel so we have our initial liquid placed onto the separating funnel with a new solvent as then agitated and the pressure is released by putting that taking the stopper out and then what we should see is we should get two layers there typically the organic layer is on top and the equates at the bottom but it can depend on what solvent that is that you're using so they may flip around but what matters is that you know which solvent it has that you want so you can then open the tap and alone the mixture to drain and then cause the tap once this level here comes down to there and then you discard that layer if you do not need the bottom one and then you take load the rest of it to go and to dream and to a different flask we would then undergo destination in order to get the exact organic product that we want after we have an organic solid then we can use a drying technique and this is very very simple where we simply just leave it in a warm place or relieve it and something called a desiccator which is this diagram here then we use a suitable drying agent and the purpose of that giant agent is to remove any water from the organic solid or even an organic liquid ethnicity so the most common drying agents are unhide rest metal salts such as calcium chloride and it absorbs the water as a water of crystallization and we can then remove the drying agent F necessity by decanting or filtration F as a liquid or effort we have an organic liquid sorry F we have an organic solid then we can simply just remove it from the desiccator lastly we can test the purity of our solid by testing the melting point or if it's a liquid we can look at the boiling point then the biggest thing where fest is that if you have any Puritans you will see a range of values for your melting or boiling point ideally we want to just see one small range once one specific value and we can then compare these with the known values for pure compounds now the problem is that with this methods is that different organic compounds can sometimes have the same melting or boiling point so if your time to determine between two substances that may have the same boiling point this method would not work so you may need to use some additional analysis such as mass spec or infrared and we'll discuss and pretend later on and another video so let's have a look at some passed favorite questions for alcohols well these are from the January 2019 paper and the first one is a multiple choice so we want to figure out which one has the tear in it alcohol is a 2-methylbutane 2:02 methyl butyl mono pent on to our pen Tampa to Rio now the best way to do this is just to draw them out so let's start off with join ear which has two methyl butyl - OH so we can see here that we have there OAH clip attacked attached to a carbon that is not attached to any other hydrogen so this is going to be tear but let's just double check our others just to be a hundred percent sure so if we have to me felt Boonton - oh we're going to have something that looks like this and we can see that this is going to be a primary alcohol because our all each group is attached to a carbon that only has one alkyl group if we have pen time - OH that gives us five carbons with foliage and we can see that we have our all H clip being attached to a carbon that is attached to two alkyl groups so this would be a secondary and D is pent on three all then again we have our own each clip attached to a carbon that is attached to two alkyl groups so paint on three O would also be a secondary alcohol which leaves us with the answer of ear so question 19 then this paper is looking at the structure properties and reactions of the alcohols ethanol and butan - all so ethanol mixes with water and all proportions but blue turn - all has a limited solubility and water part one asks us to name all the intermolecular forces that are present and these alcohols well of course they all contain electrons so they are all going to have London forces they also have that permanent dipole permanent dipole due to the presence of the Oh H grip and because it also has that hydrogen attached to an oxygen that can make way for hydrogen bonding so we have all three being attacked how all three and two molecular forces being present here you get two marks for getting three of them and one mark if you get any two and he reference anything to do with covalent bonds then your are going to be losing marks there so please make sure we understand is the intermolecular forces and then for two marks for part two explain why Bhutan 2o has a limited solubility and water well we need to think about the main forces that are going to have an effect here now we know that permanent dipole permanent dipole forces typically tend to cancel each other out so there tend not to be the strongest force overall so really we're going to be focusing on London forces and hydrogen bonding so butan - OH does form hydrogen bonds with the water apologies for that but the the problem with that is that the whilst it does form the hydrogen bonds it does also have London forces and the London forces and butan - oh are the predominant force and that just means that because they are the predominant force they are going to or they are the stronger force depending on how you want to place it we are going to have much more of an effect and these actually limit the solubility so the longer the hydrocarbon chain that is attached to the OAH grip the more predominant the London forces are they afford the list the soil the solubility that's why death UNAM which only has two carbons then it's hydrocarbon chain can't be soluble but butanol which has four is not going to be soluble Part C is looking for the structure so is looking for heating both of the alcohols under reflux with acidified potassium dichromate and then we after refluxing we get an organic product being formed then notice that were being specific that we're heating under reflux and we're heating both the ethanol which has the structure and also the butan - OH which has the structure so part one is asking for an organic product that is formed from ethanol and a chemical test to show the functional group this present well because we're heating under reflux we're going to be doing a complete oxidation which means that we're going to be making a carboxylic acid and in particular we are looking to make ethanoic acid any chemical test that we can use for ethanoic acid well there are various different tests that we can use we can be looking at how it reacts to form an ester we could also be looking for a neutralization reaction but the most common one is to simply add a metal such as magnesium and we should see effervescence if we also want to have something else for effervescence which should also say that we can add sodium carbonate and we get effervescence as well so we want to then give the structure for the organic compound that is formed from butan to O so butan to all we can see as secondary alcohol so we are going to be forming a ketone and because it just says structure it doesn't matter how you want to see it but I'm sorry how you want to draw it so I'm gonna draw it the fill structural formula so I have my four carbons and where my which was isn't there going to be a carbonyl group and then I just add then the remainder of my hydrogen's and it doesn't ask it for it but to make you aware this as butanone so you can see them that we've got the marks kings and order for you to check the answers for each of these and you can go back and try them again if you want and you can find lots of other passed paper questions on alcohols through different websites or you can check the individual unit to pass papers I hope this video has been helpful and if you do have any questions please do not hesitate to ask them in the comments and if there's anything else that you need in terms of topics that you want to revise please please please let me know and I hope to see you back on the the channel soon [Music]