Organic Chemistry

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21. Enolate Chemistry:Reactions at the Alpha-Carbon

Acid-Catalyzed Alpha-Halogentation



Acid Catalyzed

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Hey, guys, In this video, I want to talk about specific Electra Filic Alfa substitution called Alfa Halogen Nations. So it turns out that Alfa halogen nation can proceed through an acid catalyzed and a base catalyzed mechanism. I'm gonna show you both, but it's important to know that they actually yield different products because of what the intermediates look like. Okay, so the acid catalyzed mechanism is always gonna yield mono halogen nation. Okay, let me show you what this mechanism looks like. So for an acid catalyzed mechanism, this is gonna proceed through the Enel totem. Er. Okay, so we're gonna be trying to make the Enel totem. Er, the way it works is let's say you're using just h 30 plus. Okay. And you, protein E. Okay, What you're gonna wind up getting is something. Looks like this. Okay, I'll just try it like this. Okay. Double bond. Oops, that's terrible. So another one. There we go. Okay. And then we can make the Enel. The Enel would be with the conjugate base. Right? So you take off the Alfa Carbon or the alpha proton with water. My conjugate. I would do this This on this So then I get my anal totem. Er cool. Okay, so this in all is now a pretty good nuclear file, so I can use it to attack my diatonic halogen in a similar way. Not really the same way, but similar to another nuclear file. Okay, so you would go ahead, grab one of the exes, kick off one of the exes, and what you wind up getting is a molecule. Looks like this O h. With now a new X here. Okay. Oh, also, I'm sorry the mechanism would do this. You would also bring down the electrons to reform the double bond. So you would get is something like this. Okay, so that would be kind of the intermediate. Okay, Eventually, this gets deep protein ated using water and you get back to your keto form. Okay, so that's what we call our Alfa hallucination. Notice that we add an X to the Alfa position, but we only at one time now you might be wondering, Johnny, why would you? Only at once. What is it? Not that again? Well, it turns out that having the X there to pull electrons away from the alpha carbon is gonna make it less likely to Macon Enel next time because the enemy is gonna require a positive charge on that carbon. And I'm not on that carbon, but on those on those carbons and by pulling away extra electrons, you make it less likely to form an anal. So it only reacts once. Close so far, awesome.

Provide the major product for the following reaction.