Organic Chemistry

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10. Addition Reactions

Ozonolysis is a form of oxidative cleavage that breaks through alkenes and replaces them with carbonyls on both ends. Just imagine the ozone functioning like tiny atomic scissors, cutting each alkene right in half!



General properties of ozonolysis.

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So now we're going to kind of switch gears and move away from talking about strict addition reactions to talking about oxidation reactions. It turns out that double bonds not only can be added to, but they can also be oxidized. What that means is that Oxygen's could be placed directly on them. Okay, so we're gonna talk about is some different ways to do that. And what I want to talk about right now is those analysis. So those analysis would be categorized as a reaction That is a form of weak, oxidative cleavage. Okay, so what does that mean? Basically, Cleveland just means to cut something. Okay, So this entire time, we're gonna be using, like, our visual scissors to cut things, and we're gonna be cutting things in different pieces, okay? And there is a mechanism for owes analysis. It's very long If you guys need to know it for your professor, believe me, I'll teach it to you. But that's not gonna be on this page this page. I just want to give you a general overview off. What does analysis does? Okay. And what those analysis basically does, is it Slices double bonds in half and what it winds up making is a combination of key tones Aldo hides and formaldehyde. Okay, why does it make each of those things? I'll explain, but think about it this way. Imagine they have a very long carbon chains and there's one double bond in the middle, and you cut it into two. How maney change? Would you expect to have to? All right, that's pretty easy. How does have a ring and have a double bond in one part of it? And then I snippet right there. What would I expect to get it? The end. Two rings, Two chainz? No, I would just expect one chain, right, Because I had, like, a ring, and I cut it in one place. So now I have one chain thes air, just like simple geometry questions that actually get students confused with those analysis. That's exactly the way this works. So here you can see I have a seven carbon chain with two places to cut. I could use scissors here, and I could use scissors here. Okay, now, please. The scissors references just to help you guys visualize what's going on. What once is happening is that if we have a three carbon. I mean, if we have a seven carbon chain, let's say, with two cuts in it, I'm gonna wind up getting three pieces. I'm gonna get one piece of the end. I'm going to get a piece in the middle, and I'm gonna get a piece on the other end. Does that make sense? Well, the number of carbons that are on each end are going to be the number of carbons in the product. So as you can see here along this cut, I'm splitting it off with one carbon at the end. Okay. Here. Between the two cuts, I've got four carbons in the middle. That's what these numbers represent, by the way. 14 and then here it the top. I've got two carbons that are getting chopped off. So what that means is that I'm gonna expect three different products a one carbon products, a four carbon products and to carbon product. All right, now, let's look at the re agents really quick. The re agents are actually really easy for owes analysis, because it's always just gonna be ozone. 03 is ozone. So any time you see that you know this is owes. Analysis. Sometimes different professors use different re agents as the reductive work up. That's what it's called. Some will use ink and acetic acid. Some will use dimethyl sulfide. Okay, it doesn't really matter. Of course, it's important for the mechanism later on. But it's not important for the products. Both, they're gonna yield to the same thing. Okay, so what that means is that what I'm going to get? And this is the easy part. This is how we can make it is how we can use some shortcuts to make it easier. What I want you guys to do is think about it that every time you break a double bond with those analysis, what you're doing is you're adding oxygen's to both sides. So let's say that this was a dull bond that looked like that, and I split it into. What I'm gonna get afterwards is I'm just going to get a carbon deal on one side and a carbon. You, on the other notice that what I'm doing is all I'm really doing is I'm keeping the double bonds there, but I'm adding oxygen's on each end. That's all that's really happened. I'm just adding an oxygen here and oxygen there, and then I'm splitting them apart. And that's exactly what's happening with all of these different cuts. So what? The first stage I added to Oxygen's and look what I got. I got this piece and this piece. Now, where did those hydrogen is come from? Because I know that those were confusing. Well, this carbon here, this double bond always had those two hydrogen. I just wasn't drawing them. Okay, After it gets cut, it's just gonna look like that, Okay? Just you guys know this is called formaldehyde. This is the easiest. This is the simplest. Al died Aldo high. Okay, so the simplest organic alcohol, the simplest al Jehad, is formaldehyde because it just has to ages. Okay, then there was also an age here, So all I did was I drew it over here. And this would also get a carbon Neil, because once again, I'm just adding an O at the end, and I'm splitting it off. Okay, so that's that part, Then noticed that I had one other split over here. This is just it's gonna be the same thing. I'm just gonna put Oh, now notice that this part would become a key tone. Why is that? Because this double bond was already inside of two other carbon chains. There were already two carbon chain surrounding it. There was no h is coming directly off of it, so it has to be a key tone. However, the top part of the double bond had an age coming off of it. So what that means is that it's still gonna have the h and this is gonna be an alga hide. Okay, so you can remember that. Oh, analysis yields ketones. Aldo hides in formaldehyde, but you could just draw it out. And if you draw it out, everything is gonna be correct. Anyway, Even if you didn't remember, that I'll have to do is add those to the double bonds. Okay, Now, basically, ketones and Aldo hides. That would be for molecules with more than one carbon. Formaldehyde is basically just what you get when you have a one carbon chain that breaks off right here. Okay, just so you know, the molecular formula of formaldehyde is C H 20 And you might see it drawn like that as well. So you could see that it's that on the way it was drawn is that maybe you get these two products and then it would say plus C H. +20 and that just means plus formaldehyde. Alright, so I hope that makes sense to you guys. Let's go ahead and practice this with the practice problem, so go ahead and try to do this yourself and then I'll show you guys how to do it and I'll show you an easy way to do it, so it'll make it better for you, so let's go ahead and do it.

The products of ozonolysis are a mixture of ketones, aldehydes and formaldehyde. You get these with:

  1. Ends of alkenes with –R groups on both sides = Ketones
  2. Ends of alkenes with 1 –H  = Aldehydes
  3. Ends of alkenes with 2 –Hs (yielding single carbon fragments) = Formaldehyde  

General Reaction:


Predict the products of the following reaction.