Free Radical Polymerization

when radicals are exposed toe all canes in excess, they could do something really weird. And what that is is they could do something called prelim arise ation. Prelim is ation is where you basically have a chain reaction that never stops. It never has a termination step because it keeps propagating forever. Okay, so what you wind up getting is thes hydrocarbon chains. That could be 10,000, 20,000, hundreds of thousands of units long, okay? And that's actually what plastic is. A lot of synthetic materials come from prelim arise ation. So what I wanted to go over right now is just the general mechanism for these prelim ization reactions. And it is radical. Inter mediated. So basically, like I said, radical polarization reactions use Al Keene's okay in access to extend the propagation step. And this is the way that industries use petroleum petroleum just from underground. They use it and they convert it into plastic through this method. Okay, and all this is just a big chain reaction that just keeps on going. And that's how you get stuff like tires and shopping bag or whatever. You know, all these different things that are made out of weird plastics, All these synthetic materials, it's it's basically petroleum, just linking up in cross linking. So basically, here's a really common, um, byproduct of petroleum propylene on. Believe me, like they wind up, they mind tons of this stuff. They drill it and you get tons that stuff from underground if you do a prelim arise ation reaction using some kind of radical. Okay, so I'm just gonna put here a radical initiator like, oh, are negative. I mean, not negative radical. We wind up getting is a polymer, and the general formula for a polymer is basically end is just the number of units, okay. And we don't really know how many units that are so and is just going to stay like that. Okay. What? It means that you have these repeating sub units that just keep going on forever. Okay, In this case, this repeating sub unit would have basically two carbons and then another carbon here. Okay? The way that works is that the two carbons in between are always the ones that are made out of the double bond. Okay, so in this case, that would represent these two right here. Okay, this extra ch three at the top. What's that got to do with? Well, that's the ch through right here. Okay. All the other h is that air around are the other ages that air sticking out of this thing. So there's an H, h and H, and these three inches are the three ages right there. Okay. And this just keeps extending and extending. And actually, polypropylene is used to make, like, astro turf and rug and car tires and ropes and stuff. Okay, so it's kind of cool how it actually has a real life application.

Let's just get into the mechanism, though, because I know that's what you're interested in. So the general mechanism is of course, we need an initiation step. So we're gonna go ahead, and in this case, we use peroxide. Usually that's the one that the industry uses. So we would get to equivalents of my peroxide radical. Okay. And that's going to react with my double bond. Okay, Now, in this case, the radical is going to react directly with the double bond because the double bond is a good source of electrons. So what I wind up getting is just going to show you guys right here, three arrows. Once again, I'm going to get, um, this going out into the middle of nowhere. Then I'm gonna get the double bond attacking. Now, I just have to ask myself, where would the radical the extra radical be most stable on the primary Carbon, The red one or on the secondary? Carbon, the blue one. The answer is secondary. So my radical would go ahead and jump there. What I would get for this first step is I would get now. Oh, are okay. And I would get Well, there's no more double bond anymore. She's a single bond with a radical. Okay, so that's my first step. Well, now, how is that going to propagate? Well, that's gonna attach toe another radical, so I mean to another double bond. So what winds up happening is that now this is going to do the same thing again? I'm going to get 123 This is the whole idea behind polyamory ization. It's gonna keep doing the same thing over and over. So what I wind up getting here now is I'm gonna draw the blue part just the way it was before, but watch, I'm gonna twist it a little bit. So now this goes here and that sage three that I had basically there. That's, like, not participating in blue. I'm gonna move that one up. Okay, so that means that now, what is that attached to? Well, that there's a new single bond. I'm gonna make that black. That represents the new single one that was made by the radical reaction, and that's gonna be attached to a new to a new three carbon sub unit that now has a radical there. Okay. And this is going to keep on going and going. Going. So what you see is that now we have our general formula starting a prop up. This is gonna be the repeating sub unit is gonna look like this. Okay, We're basically I have this thing that just keeps going over and over and over again. Okay, so what about determination? Step? You're curious about that? We're just gonna put here n a Why? Because that's the whole point of polarization is that there is no termination step. It just doesn't terminate. It just keeps on going forever until you run out of Al Queens. Okay, on what you end up getting is thes really, really, really long polymers. You have unusual properties, like being elastic and never bio degrading and stuff like that being terrible for the earth and killing animals. So what I want you guys to do now that that sounded like, really jaded. But what I want you guys to do now is just figure out what the General sub Unit would look like if we were to prelim arise this molecule. Okay. And the best way to do that would just be thio kind of draw. The first parts of the mechanism and see if you guys can figure out what that repeating sub unit is gonna look like. There, that's called the general formula of the flow of the polymer would be in those brackets. So I'm gonna give you guys some time to do it. Go ahead and use. You have to draw the whole mechanism. But use O R E. Keep saying negative. Use the O. R. Radical to start the reaction and then kind of just continue it and see if you can get that repeating sub unit and then I'll give you guys the answer.

So let's just draw this from the beginning. What I would have is that my I just draw a little bit closer. I would get three arrows. 123 in this case, noticed that both carbons were exactly the same in terms of their substitue INTs. So it didn't matter where he put the radical. Okay, so now what I'm gonna do is I'm gonna draw something. It looks like this I'm gonna have Oh, are with a single bond with a single bond. And the radical would be over on this side because on the opposite side to wherever the O. R. Attached to you. And those are the two carbons. Basically, this is, let's say this is carbon one, and this is carbon to This is carbon one. And this is carbon too. It's not just let's figure out what goes on each of these, and it looks like it's chlorine. So one is going to get a chlorine. She was gonna get a chlorine. Okay, Now I have that radical there. Let's react it again. It's not gonna react it with another Al Keen. So I'm gonna get this this and that and what that's gonna give me is now. I have the same exact thing is before CEO CEO, But now that's attached to what? Well, that's gonna have a new bond. And that new bond is going to be a touched with two carbon chain with C l and SEAL. Are we starting to see a repeating sub unit? Yes. So what that means is that my repeating sub unit would look like this. So it just basically just one just one equivalent of this. So it would be that I Let's say I take my this, this portion of it right here, Okay? And I say that I have a seal at the top and a seal at the bottom. But I also have an H at the top, and I also have in each of the bottom, okay. And then I would just go ahead and draw the lions going out of it. And that just means that there's other stuff attached to it. Okay. And that's really it. We're done. That's all you needed to dio. Okay, um and then you just keep adding these subunits and this would make its own polymer. That has its own unique synthetic qualities. Alright, so I hope that made sense. It's not a terrible mechanism, but it's just something interesting that radicals do, and it is obviously something that might be fair game for your exam.