 The another one we have here is condensation polymerization. Okay. So in condensation polymerization, what happens? Like I said, the neutral molecules like H2O, LH3 goes out. So the second reaction we have, look at this reaction. This molecule reacts with glycol, which is HO CH2CH2OH. So what happens in this? When you heat this, H2O molecules goes out. H2O molecules goes out. And these two combine to minus H2O. And the product will be HO, Cdb bond O, a benzene ring, Cdb bond O, O CH2 CH2. Okay. This molecule, the name of this molecule is terfithalic acid. And this one is glycol. The polymer that you get here, we call it as pteriline polyester or daikon. I'll write down the name. But first of all, you see here, these two combines. And in the next step, since we have two different monomers here, so which one we can use in the next step to get the large complex structure, polymer structure, which of these two monomers we should use in the next step? Tell me. If we want complexity and terfithalic. Which one? Acid thing. Actually, you see this end is an acid, right? This end is an acid and this is an alcohol. So actually, we can use any one of these monomers in the next step. The only thing is if you use alcohol here, the reaction takes place to the acid end. If you take acid here, then the reaction takes place to the alcohol end. Got it? Right. So now you see, suppose I am taking this acid in the next step, which is in short, I'll write down pH, COOH and COOH. Then the reaction takes place here, right? Alcohol end. From here to this CH2, the thing will be same. The structure is HO, C double bond O, C double bond O, OCH2, CH2. And then again, H2O goes out. So this connect with an oxygen, C double bond O, then benzene ring, C double bond O, OCH. Take a C double bond O, OCH. Now you see here, in the next step, now we are bound to use what? We are bound to use? Only the alcohol. Because both end we have what? We have acid. So basically, we will go alternate in this way. Okay. First, we can use in the first step, we get this, and then we can use any one of these monomers, alcohol or acid. But if you use alcohol here, next will be acid. If you use acid here, next will be alcohol. And like that will go alternate. Okay. Now the thing is, if this reaction takes place, I'll write down one more step here. The product is this. We get after this reaction, the product is this. We have HO, C double bond O, C double bond O, OCH2, CH2, OCH2, and then we have a ring, C double bond O, OCH2, CH2. This is the product we get after this reaction. Now you tell me here, what is the repeating unit for this monomer, for this volume? Give me a minute, I'm coming. Tell me, find out the repeating unit in this. Yes, tell me. The repeating unit. So is it O, C double bond O, phenyl C double bond O, O, CH2, CH2, O? I think it's only till CH2, CH2. Till CH2, CH2? Oh yeah. That comes from the other thing. Okay. So the repeating unit here is from this C double bond O, we'll take this here, this C double bond O to this oxygen. One change I have to do. This is, this side also the change we have, which is OH here, and this will take this hydrogen, this hydrogen. So repeating unit is this. So this you should know for a given polymer. And what kind of the name of this polymer is, we call it as pteriline, okay, which we also know as, this has polyester because you see COO, R group we have. So it is polyester, okay. And the common name is Dachron also, D-A-C-R-O-N. Okay. So all these names are important. So basically Dachron or polyester or pteriline, is it a copolymer or homopolymer? It's a copolymer. It is a copolymer because two different monomer we are using. That's what you need to keep in mind. Okay. The difference in this condensation and addition polymerization is what? That this reaction we can stop at any step. You won't heat it, reaction won't go in the next step. Okay. So this can be stopped. The reaction is under control. That's what we can say. The reaction is under control. Unlike the addition polymerization, where we have no control on the reaction. So that's the difference we have here. Okay. Some more example we'll see. Can you tell me the formula of adipic acid? Yes. Don't know, sir. Don't know. I have given you this though in carboxylic acid test. Could you repeat which acid? Adipic acid. Just a second. Adipic acid. Don't know. Do you remember this? CH2. COOH. Here we have COOH. And this is N times. So if N is zero, what is the name of the molecule? Because it is COOH, COOH. Because there's no CH2 present in between. When N is zero. When N is one, malonic acid. When N is two, succinic acid. When N is three, glutaric acid. When N is four, it is adipic acid. And when N is five, it is pymalic acid. Okay. So I have given you this. How do you memorize this? Zero to five N. OMSGAP. Do you remember this? Ohm's cap. Yes. So this you must remember. It helps you in, you know, getting the formula of the molecule. So adipic acid and hexamethylene diamine. So adipic acid, the formula is HOOC, CH2. What is the N value for adipic acid? Four. So this is four. COOH. And this combines with hexamethylene diamine. Okay. So hexamethylene diamine is this. CH2, NH2. Here also we have NH2. Hexamethylene, so CH2, six. So second one is this molecule is hexamethylene diamine. Okay. When condensation takes place between the two, H2O molecules goes out. And it forms the product here is HOC double bond O. CH2, four C double bond O. O combines with NH. Should we have O? We don't have O here. Sorry. C double bond O. OH and H forms H2O. And it gives NHCH2, six NH2. Is the compound we get? The repeating unit, if you see, it is from this C double bond O to, I'll write down this way with hydrogen. The repeating unit will be from here to this hydrogen. N times of this gives you the polymers. Okay. So this molecule, this polymer, in general we call it as polyamide. Why polyamide? Because in this we have amide linkage, CO, NH bond. So it is an amide linkage. Okay. So in the polymer like this, we have many amide linkage. That's why we call it as polyamide. Okay. And this commercial name of polyamide, we also call it as nylon. What? Six, six. Sir, does condensation polymerization happen only for copolymers? Not necessary. It is possible with homopolymers also. If you have suppose two molecules of adipic acid, then also it's possible. Okay. But yes, in that case, you'll get a molecule which has a bond of C double bond O, O, C double bond O. Okay. So that is an ester kind of molecule you'll get. But it is possible with homopolymers also, inhomopolymers also. Like two carboxylic acid may combines, no, for the molecules to go out, goes out. So it is possible over there also. Condition will be different. It may stop after a dimer itself, no, sir. Because dimer is also a polymer, no. And why would it stop? Suppose one end we have this end, we have CO, OH open. Okay. Then we can take another same. This end will react. It is open. Now, suppose we have CO, OH, CO as you said also. These two react. You'll get a dimer. This end and this end is open. So now this end will react or this end will react. So like this, it goes. If condition is not there, then it stops, huh? Won't there be any repulsion because it's the same type? If you compare, yes, there will be. But the question, whether it is possible or not, it's possible. Yes, yes. Okay. Thank you. Yeah. Nylon 6, 6 is a commercial name for this. This 6 and 6 stands for the number of carbon atom in the two monomer. Here you see. The number of carbon atom is 6, 4, 5, and 6. So this 6 and 6 represents, right down here, the number of carbon atom present in the monomer. Okay. This polyamides. Nylon 6 to 6 is a polyamide. Okay. It has amide linkage. Hence it is polyamide. CO and H.