Now we're going to take a look at the other form of beta dicarbonyl ester reactions, which is malonic ester synthesis. You see this chart, and you're thinking, "Oh my gosh, another set of reagents that I need to memorize," and you're probably getting depressed. But don't. This is the same exact thing as acetoacetic ester. Notice that every single reagent here hasn't changed. Nothing has changed. The only difference is that because I'm starting off with malonic ester, I have an extra OET group over here. What that means is that after I hydrolyze, not just this one turns into carboxylic acid. They both do. That means that the only difference between acetoacetic ester and malonic ester synthesis is that my products have carboxylic acids at the end. That's it. Everything else stays the same. You could literally take everything you learned from acetoacetic acid and, when you see malonic, just draw the same thing as acetoacetic acid and add the carboxylic acid at the end. I'm not even going to go over every reaction here because this is the same as acetoacetic ester. Let's go through this practice problem. Go ahead and try to solve it yourself, and then I'll step in and help.
Malonic Ester Synthesis - Online Tutor, Practice Problems & Exam Prep
General Reactions
Video transcript
Predict the Products
Video transcript
One word of caution here. If you feel like you couldn't get this question right because you're having a hard time interpreting this condensed structure, you probably need to go back and review condensed structures. Just saying because we're pretty late in Orgo 2 and they could show up anywhere. Condensed structures, I do have videos about them. If you need extra help, I got you. But anyway, the way you interpret this was it's a carbon with these 2 esters coming off of it. It would be COOET. That would be like that and like that. And then obviously it's CH₂, so I'm just going to put HH. Again, this is just another way to write malonic ester. The first step was my base. Do you think that this base was a good choice for this ester? Sure. The R group is the same. I don't have to worry about transesterification. The negative is going to grab one of the H's and make an enolate. I'm going to make something that looks like this. Now that enolate is going to be exposed to the following alkyl halide, something like this. Cl carbon carbon Just make sure I'm getting this right. CH₃₂ then CH₂. Yep, that's right. Then we're going to do a backside attack. What that's going to give us is now a malonic ester that is substituted And what's attached now is I have my new bond. Well, I want to use a different color. I have my new bond and then I have the thing that I attached. So 1, 2. I believe that's right. Wait. Making sure I think I'm actually off. Yes. It should actually be that is that and then that is that. Perfect. Just making sure it's not a bad idea to slow it down and make sure that What's important about hydrolysis here is that you're going to hydrolyze What's important about hydrolysis here is that you're going to hydrolyze both of your esters. That means that you're going to get carboxylic acid on one side and carboxylic acid on the other. You can't stop it. Plus your R group. Then finally, we have decarboxylation. You might be wondering how do I know which one to decarboxylate because we said that carboxylic acid can decarboxylate. It doesn't matter which one. You could either take off the green one or you could take off the red one, but you can't take off both. Pick 1, make it go away, the other one stays. Let's just say the red one leaves. That's going to give me a final compound that looks like this. O H carbon. What's that attached to? Carbon, carbon. 1, 2, 3, 1, 2, 3, something like that, plus my CO₂ gas. Notice that once again, I just did an alpha alkylation, but I used malonic ester to do it and notice that I have a carboxylic acid as the end product because I started off with malonic ester. I hope that made sense. It's not as scary as it looks. It's actually really fun. This is actually one of my favorite reactions students like it. That being said, let's move on to the next videos.
Provide the major product for the following reaction
Provide the major product for the following reaction
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