11. Radical Reactions
Free Radical Polymerization
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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 going to go ahead and in this case, we use peroxide usually. That's the one that the industry uses, so we would get 2 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 I'm just going to show you guys right here. Three arrows once again. I'm going to get this going out into the middle of nowhere. Then I'm going to 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 O R. K. And I would get well, there's no more double bond anymore. It's just a single bond with a radical. Okay? So that's my first step. Well, now how is that gonna propagate? Well, that's gonna attach to 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 1, 2, 3. And this is the whole idea behind polymerization. It's going to keep doing the same thing over and over. So what I wind up getting here now is I'm going to draw the blue part just the way it was before, but watch. I'm going to twist it a little bit. So now this goes here and that CH 3 that I had basically there that's like not participating in blue, I'm going to move that one up. Okay? So that means that now what is that attached to? Well, there's a new single bond. I'm going to make that black. That represents the new single bond that was made by the radical reaction. And that's going to be attached to a new 3 carbon subunit that now has a radical there. Okay? And this is going to keep on going and going and going. So what you see is that now we have our general formula starting to pop up. This is going to be the repeating subunit is going to look like this. Okay? Where basically I have this thing that just keeps going over and over and over again. Okay? So what about the termination step? I know you're curious about that. We're just going to put here NA. Why? Because that's the whole point of polymerization is that there is no termination step. It just doesn't terminate. It just keeps on going forever until you run out of alkenes. Okay? And what you wind up getting is these really, really, really long polymers that have unusual properties like being elastic and never biodegrading and stuff like that. Being terrible for the earth and killing animals. So what I want you guys to do now that sounded like really jaded. What I want you guys to do now is just figure out what the general subunit would look like if we were to polymerize this molecule. The best way to do that would just be to kind of draw the first parts of the mechanism and see if you guys can figure out what that repeating subunit is going to look like there. That's called the general formula of the polymer would be in those brackets. So I'm going to give you guys some time to do it. Go ahead and use you don't have to draw the whole mechanism, but use O R I 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 subunit and then I'll give you guys the answer.
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