A simple polyamide can be made from ethylenediamine and oxalic acid (Table 17.1). Draw the polymer formed when three units of ethylenediamine reacts with two units of oxalic acid.

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Hi, everyone. Welcome back. Here's our next problem. A simple polyamide nylon 66 can be made from the condensation polymerization of hexane 16 diamine and adip acid illustrate the polymer that emerges when hexane 160 diamine reacts with the acid. We have four different answer choices here, four different line structures of polymers. So we'll go through these more thoroughly and talk about them after we think about what reaction we're expecting to take place. So we're generating a polyamide with a condensation polymerization. The base reaction we're looking at here is the reaction of a carboxylic acid with an amine super juice and amid less water. That's why it's a condensation. You're eliminating a water molecule. So we recall our carboxylic acid general form would be an R group bound to a carbon molecule that's in a carbon group. So C double bonded to an O and then with the S that's he has a single bond to an oh group. And then our amine would be in the form of H NR two prime. Keeping in mind that this sort of general format looks like a secondary. I mean, I mean, it could be a primary, I mean, as well where you'd have two hydrogens, instead of a second R group, you'd have a ni a hydrogen and just one R group. And then that would produce an amid, which would be in the format of R with the carbon ca carbon bonded to it. And then instead of the, oh, you've eliminated the, oh from your carboxylic acid, you've eliminated the hydrogen from your amine. That's what generates your water molecule. And you've produced this amid. So we have your r carbonel group and then you have your nr two prime plus water, of course. So what happens? Of course, in polymerization is that we have a molecule that's a dic carboxylic acid. So it's got carboxylic acid groups at both ends with a diamine amine groups at both ends. So you can have this condensation reaction between the end of your dic carboxylic acid, your beginning of your diamine at the end of the diamine that amine group can react with the beginning of another dic carboxylic acid and you make this chain. So let's think about the specific molecules in our case that are reacting in this polymerization. So in our case, our dic carboxylic acid is APIC acid. This is a six carbon chain with carboxyl groups at both ends. So we'll start with our first carboxylic acid group. So we have h oh bonded to that carbonel group. And then we have our four internal carbons since our functional group itself, each of those has a carbon in it to make a six carbon chain, we need four ch two groups. So in parentheses, ch two subscript four and then that will be bonded to another carbonel group which will then have a bond to, oh so six carbon chain, carboxylic acid groups on both ends. That's our aic A and then our diamine, in this case is hexane 16 diamine. So we have a main groups on both ends and then six carbon chain in the middle. So we'd have, again, this is a primary meme. So it has two hydrogens on the nitrogen. So H two N bonded two, a six carbon chain. So CH two in parentheses, subscript six and then NH two. So that's our diamine there. So now let's think about what the result will be when these react. Well, again, if we imagine the two first molecules coming together, we eliminate the oh group and we eliminate one from the end of the epic acid and one of the hydrogens from our amine and our structure, we'll have, we'll start with our first molecule here of epic acid ho carbon group, ch 244 of those units, another carbonel group now that carbon carbon will be bonded to the nitrogen, which still has one hydrogen left and then it has its six carbon chain, ch two subscript six. Now we started in toward diamine molecule. So it will finish up with another nitrogen. But this end nitrogen will be reacting with the next molecule of dic carboxylic acid. So it will now just be NH and it will form a bond with a carbon carbon. Now, we're into another molecule of our adip acid. So now we have our ch two subscript four and then so forth, we reach the end of the screen. But again, it will just continue on another carboxylic acid group just repeating the unit that we have right here. So to help us remember as a polymer at the left side of what I've written where I had my first molecule of my carbolic acid. I'm going to erase that. Oh To imagine the polymer structure just have a line for the bond from the carbon carbon and put a bracket there showing that's the going to be this repeating unit. So now let's compare the structure that I've determined for a polymer with the answer choices to see which of these matches what we know will be the product. Well, in choice A, we see we started the polymer added nitrogen. So we have NH and then we have a benzene ring. So in choice A, we actually have the wrong dic carboxylic acid. AIC acid does not have a benzene ring. So choice A can be eliminated. And this is an example of where common names, even though they're less unwieldy and can be easier to say can be confusing because if we mix up which common name belongs to which acid we might come up with this structure. Whereas with the IOP names as bulky as they are, we at least know what groups we should have in our molecule. But choice A is incorrect. Let's move on to. Choice B. Choice B starts with NH, but then that nitrogen is bonded to another NH group. Well, when we make our structure, we never have a nitrogen bonded directly to another nitrogen. It has a carbon group on one end. And then it's our group on the other. So this cannot be correct since we wouldn't expect any NN bonds. So choice B is incorrect. Now, let's look at choice C starts with a nitrogen bonded to a carbon carbon. So that's correct. We'd expect that. And then we see we've got a string of ch two groups. Well, how many we have will tell us which molecule we've moved into here. So we have here, 1234 carbons. So this is the inside of the dic carboxylic acid which has four ch two groups. So we see we're at the end of the amine and the beginning of the carboxylic acid. So if we want to see where this corresponds to in our structure, we'll look for where we have nitrogen, then carbon and then four ch two groups. And that's at the end of the structure we've drawn. So the second nitrogen from our, originally from our diamine going to put a red bracket in front of that and then you see the idea of a carbon carbon and then our ch two subscript four. So right, where we're running off the page is where sort of in the middle of where our answer choice draws that structure. So we know, yes, then we'd expect another carbon carbon bonded to the beginning of another one of those diamine molecules. And we see NH So choice C is our correct answer here. We can just be extra. Sure. By checking on choice D, choice D starts with the nitrogen molecule but there's no other hydrogen on this one. So that's incorrect. Then it has a carbon carbon and that's bonded to a carbon with an oh group. We should not have any oh group. Well as the missing hydrogen on that first nitrogen, there should not be any oh groups left in our product. So choice D is incorrect. We'll cross that out and we are confirmed that choice C is indeed our correct answer. This is the structure of nylon 66 as this polymer caused from the condensation polymerization of hexane 16 diamine and adip acid. See you in the next video.

A simple polyamide can be made from ethylenediamine and oxalic acid (Table 17.1). Draw the polymer formed when three units of ethylenediamine reacts with two units of oxalic acid.

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Key Concepts

Polyamide Formation

Condensation Reaction

Structural Representation of Polymers