Predict the mechanism for the following reactions. Provide the...

Question

Predict the mechanism for the following reactions. Provide the full mechanism and draw the final product.

Chemical reaction diagram showing elimination mechanism with acetone and a cyclic compound.

Accepted Answer

All right, guys. So what mechanism did you guys get? It should have been e 2. Okay? Why is that? I'll tell you why. We're going to use the flowchart. So the first step was is this negative or neutral? It was negative because I had a sodium. So I had a negative charge right there. Okay? So now my second step was, is this one of my bulky bases? No. It's not. So then my 3rd step was what kind of alkyl halide do I have or a leaving group? Look what I got again. One of those pesky sulfonate esters. All right? And that's gonna be secondary. So I have a secondary leaving group. So that means that I'm gonna have to make one more decision, which is the 4th one. Is this a better is my nucleophile a better base or is it a better nucleophile? So you have to think, is this molecule here on my good bases list? Yes, it is. This was actually the 2nd base on the list. It's an alkynide. Remember that I said that alkynides are strong bases? So what that means is that this is going to be better at doing an elimination than a substitution. So since it's a good base, we're going to consider this e 2. Is that okay so far? Cool. So now that this is e 2, we have to remember everything about the mechanism. Where do we start with E2? Do you guys remember? We have to find beta protons, just like always. Okay? So where is my alpha? My alpha is here. So I have 2 betas. Right? I've got a beta at the top. I'll call it on the green one. I got a beta at the bottom. I'll call it on the blue one. Are they equivalent? Are they the same thing? No. The top one doesn't have a methyl, the bottom one does. So they're obviously different. Okay? Do they both have at least 1 hydrogen? Yeah, they do. The beta at the top, notice that the beta at the top actually has 2. It has a hydrogen in the front and and a hydrogen in the back. And the blue one just has 1, but that's fine. It's a hydrogen in the back. So really, we actually have 3 total hydrogens, but 2 different types of hydrogens. Are you guys following me so far? So here's the big question, how many final products did you guys draw? Did you draw 2? That would be wrong. If you drew 2, that's actually the wrong answer and you got 0 credit on this question and your professor tricked you. Okay? Why is that? Can anyone help me answer that question? I know someone's dying too. It's because of anticoplanar. Remember that I told you guys that every time you hear E2, from before when I told you about E2, you have to remember that anticoplanar is required. That means that your leaving group and your beta hydrogen have to be anti to each other. So how many of these hydrogens, out of the 3 hydrogens I have possible, how many of them are actually anti? This one's on the dash, which means that the little top. So now let's go ahead and draw our mechanism. And at this point, if you got this far, then you're just a rock star and you got the question right. It's just gonna be in you grab this h, then you make a double bond between the alpha and the beta, and you kick out your leaving group, and your final answer should look like this with a dol bond here. That's where the distinction is going to come, the dol bond there and your methyl group there and obviously plus your leaving group. Okay? So anyway, like I told you guys earlier when we were discussing E2, this is one of the hardest types of problems that you guys can get. And that's why you just need to practice it. This is nothing but practice. It's about recognizing this over and over so that by the time you get to your test, it's second nature to look for anticoplanar. Because I know that 90% of you guys forgot to think about that and why you need to practice it. That's why this chapter is hard because you have to practice. Now, one more note I just wanted to make. Notice that in all 6 of these mechanisms, I completely ignored the solvent if there is one. If there was one. Acetone was here. DMF was here. DMSO was here. I completely ignored them. I didn't have them in my decision making process. That's the way I want you guys to think when you're on the test. It's good to know what the solvents are for conceptual purposes, but for these questions, I don't want you thinking about them. Alright? It's just a distraction. It's not going to actually help you get the mechanism at at the end. Alright? So I hope that made sense to you guys. Let me know if this video helped you or if these questions helped you. But Also, let me know if there's anything I could do to explain it better. All right? So let's move on.

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Predict the mechanism for the following reactions. Provide the full mechanism and draw the final product.

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