hi youtube's mr lim here again and this time we're going to be instead of putting together monomers into polymers we're going to be breaking apart polymers and monomers and working out what they are so we're working on how to identify the monomers of condensation polymers both polyesters and polyamines from diagrams of the repeating units okay so um the asymmetrical nature of esters and amide bonds and polyesters and polyamides means that you should be able to tell which parts of the backbone were linked to the carboxylic acid and which parts were linked to the alcohol or amine group okay so this is the ester group where things on this side has the alcohol and things on that side has the carboxylic acid and then here's the amine group where things on this side has the amines and things on that side have the alcohol oh sorry not the alcohol the carboxylic acid okay so that's the asymmetrical nature of them okay um so let's look at polyesters the single bot uh bonded o indicates the break between the monomers okay the side of the carbon with double bonded o is the side with carboxylic acid that's what we said before so that side there is the carboxylic acid this is indicates where the break is right and the side with the o is the alcohol and the side of that side is the carboxylic acid okay all right so yep we said that already okay so remember the polymers can come from one or two monomers you can tell by seeing if the ester groups that all face the same way or if they alternate so what does that mean if the esters all go like this yep they all go like that it means that they've come from one monomer but if you see them look like this so they're going in opposite directions it means that they've come from two monomers okay so see that that one there goes that way that one goes that way that one goes this way that one goes this way so you can see how they are directional so they all go in the same direction then it comes from one monomer if they go from two different directions they go in from from two monomers okay then the alcohols that have two functional groups on them they can be on non-terminal carbons so therefore you have to think about where the side groups are in relation to the actual molecule and then the side chains of the backbone which are those things that aren't between the two functional groups they must be included in your diagrams as well okay so let's try and break apart this thing okay so as we said the o is where it breaks so here here here and here okay those are where it breaks so we should be able to see that okay well this thing goes that way things thing goes that way this thing goes that way this thing goes that way which means it's from two monomers okay and hopefully you'll be able to see that this is one monomer and this is one monomer okay and then it repeats back to this monomer because they have exactly the same and this one is that monomer okay so that should be fairly straightforward okay so the side with the carbon with the double bond is the carboxylic acid end so we're going to draw out the carboxylic acid it has four one two three four carbons so you've got four carbons here are your uh here are your double bonded o's and this is the carboxylic acids here and then you got a couple of hydrogens there okay so that's your first monomer butane diaoic acid all right the other monomer is here that's the alcohol side it's only got two carbons between the two alcohol functional groups and so this is ethan 1 2 dial okay nice and easy one to start let's try another one oh more stuff okay so here's where we're cutting them wherever the o is that's where we're cutting them and you should recognize that that's one monomer that's one monomer oops i should do that a different color that's another monomer okay that's another monomer here that's another monomer that's another monomer okay you should also be able to recognize that these structures here go that way there that way there oops a little bit more that way there that way there and that way there okay so since they're going in alternating directions therefore it's made up of two monomers and we've kind of already established that okay so let's draw these out so this one here of a blue one will be one two three carbons between the two carboxylic acid groups okay and then it's got ch2ch3 okay so there's an ethyl group in between the three chain dioic acid so this is an ethyl propandioic acid do i need to give a number no because there's nowhere else the ethyl group can go also you'll notice that the longest chain here is technically four however because the longest chain does not contain both of the functional groups that uh that's technically not the longest chain so the longest chain is actually only three okay so this is methylpropandioic acid then let's draw out the red iso uh alcohol okay so uh you can tell that it's the alcohol because this one is the carboxylic acid because it has the double bonded os okay so that one's going to be how many carbons between the alcohols one two three okay then on this one here we have a methyl group and on this one here we have a methyl group okay now here because you can make the longest chain like this all right and both functional groups are on the longest chain because then alcohol is not on the terminal carbon that makes this a pentene and it's two four two four pentandil two four pentadial all right so that's uh this particular one here okay let's have a look at this one here so here are the cuts okay and what you might notice immediately is that okay well let's look at the directions of the esters groups and they all go in the same direction and if they all go in the same direction it means it's only one type of monomer so that's the monomer that's the same monomer and that's the same monomer right and it's trying to trick you because it's like oh my god why is that one on top and that one on the bottom right but they are in exactly the same position okay so let's draw this one out how many carbons are there between the alcohol and the carboxylic acid one two three one two three because that's where the breaks are okay between the breaks okay so one two three carbons between the uh carboxylic acid which is on we'll just store it on this side and the alcohol which is on this side all right i can draw a ch3 the methyl group there and then the rest of them just have your hydrogens on it okay so we're looking for the longest chain that has all the functional groups is it just this three no it's not because you can have all because the alcohol is on that side the longest chain is a four the alcohol just isn't on a terminal carbon it's a secondary alcohol so what's that that's a butane uh no it's a hydroxy what number is it on it's on number three so it's a three hydroxy oec acid 3-hydroxybutynoic acid okay let's have a look at another one polyamines this time the n indicates the break between the monomers the side of the double bonded o is the side with the carboxylic acid the side of the uh oops the side without the carbon with the double bond o is the side of the amine blah blah blah okay so remember the polymer can come from one or two monomers uh you can tell by this telling if the amine groups face the same way or if they alternate uh amines don't have to be on terminal carbons and the side chains must be included so let's have a look at this one here so let's see where the cuts are wherever the ends are is where the cuts are okay so that's there that's there that's there that's there let's have a look at the directions of the ester groups or sorry for amide groups that one's going that way that one's going that way that one's going that way that one's going that way that one's going that way that one's going that way okay so they alternate so therefore it's two monomers and maybe you probably saw it already but here's one monomer that's the same monomer that's the same monomer here's that same monomer here's that same monomer okay so let's draw this so now quickly uh three carbons between the carboxylic acid groups and how do i know that's carboxylic acids because that's where the double bonded o's are okay so carboxylic acid here it's a propandioic acid nice and easy this one here oh it's a circle oh i love circles it's a cyclobutane with two amine groups on it okay so this is a one three one three but cyclobutane diamine one three cyclobutane diamine okay um and you've got carbon and you've got hydrogens over there and there okay cool and then last one wherever cuts the cut is here the cut is here the cup is here you look at the direction of the amide groups oh look they're all going in the same direction okay which means it's just made out of one monomer okay that's the monomer that's the monomer that's the monomer actually that's not a monomer because like you know there's no co over there so let's draw one of those it's a benzene ring okay with a amino acid on that side okay it's because here's that benzene ring here's that amino acid so it's the amino acid on one side and on the exact opposite side so that's right around to the other side is the amine group okay so this is a four amino benzoic acid all right four amino benzoic acid because this is the carbon one two three and four okay so one four amino benzoic acid is what this substance is and that's it uh you have a go at some of the questions that i've put up on sector and stuff like that and see how you go