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Organic Chemistry

Learn the toughest concepts covered in Organic Chemistry with step-by-step video tutorials and practice problems by world-class tutors.

21. Enolate Chemistry:Reactions at the Alpha-Carbon

Tautomers of Dicarbonyl Compounds


Tautomers of Dicarbonyls

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Hey, guys, in this video, I want to discuss the specific ta tumors of die carbon compounds. So, guys, I've already introduced the fact that taught Immers happened to carbon eels, whether you like it or not. Okay, this is just a natural process that occurs in equilibrium. Now. Just because it happens doesn't mean that it happens a very appreciable amounts. Okay. In fact, most carbon compounds are gonna favor the Keto totem. Er, why? Thermal dynamics, guys, it's just more stable. The Keto Tanamor is more stable than a vinyl alcohol. Okay, but beta die. Carbon eels are special, Okay? Because beta die. Carbon eels are shaped in such a way that they're actually gonna favor the n old Tanamor. How do we explain that? Let's look at the betas are carbon you'll for a second? First of all, it's defined beta die carbon deal that you have one carbon eel and another one beta to the one that you currently have. Okay, now we remember that the Alfa Carbon of a carbon eel has a Peca of around 20. Okay, so these air Pekka is that we're talking about here. Does anyone want to take a stab at what the Pekka is between a beta die, Carbonell. What's the what's the Peca of this hydrogen here? Notice that now it has to carbon nails on both sides. Guys, this is gonna be a ridiculous peek. A of 10. Okay, dependent. 9 11 13 around that area. Okay, how do you explain that? That's a crazy city. That's like za siddiq as ammonia. That's as acidic as N H four. Positive with a positive charge. How do you get something that acidic Justin Out came guys, Because the stability of the Enel Tanamor. Okay, look at what the ultimate is gonna look like The eagle Tanamor. First of all, you're gonna have to talk numbers that are possible. And what you're gonna get, first of all, is a bunch of overlapping resonance. Um, Adams, that can resonate. This is called conjugation. Conjugation makes molecules stable. Right? Awesome. So conjugation is going to stabilize these guys. On top of that, we've even got hydrogen bonding because the Enel is gonna be able to the Enel from one side is gonna be able to hydrogen bond with the Keto from the other. This is the Enel side, and this is the Keto side, it's gonna be able to hide hydrogen bond with itself. So what winds up happening is that if you take away a proton from the beta die Carbondale, the methylene carbon in the middle, it's actually gonna get 75% Enel equilibrium, depending on what our groups are. Obviously. I mean, if these are groups are different things, the number will change a little bit. I'm just letting you know this is an extremely favored taught memorization. Okay, So baited by carbon compounds are exceptionally acidic due to the high stability of the conjugate base. Okay, now, one thing to keep in mind is that since this is gonna happen so frequently, if you happen to have a Cairo center at the Alfa Carbon So let's say that this had been a Cairo center. It's not now because I got to Asians. But if it was a Carl center, that Karl Center will always be Rasim ized. Okay, What the heck does that mean? It just means that you can't isolate one in anti humor. You're gonna wind up getting a mixture of both 50 50. Why? Because when you form the Enel, you're gonna lose your stereo chemistry, you're gonna turn tribunal plainer. You're gonna lose the wedge and dash, um, structure. And then when you add, you could either add the proton from the front or from the back. So you're going to get a rationalization off any Alfa carbon. That's pretty much as a rule. You're gonna Rasim eyes all of your Alfa carbons. Okay, Awesome guys. So this being said baited A carbon nails are very important for organic synthesis because they're so good at doing Todd memorization. So let's do this problem here. I want you guys to look at the problem and evaluate which of these bands of carbon eels is gonna be the most acidic one of all. Think about the one that conform the most ta tumors. Okay, so do that. And then I'll answer

Acidic Ketones

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all right. So I'm actually just gonna go through these. Pekka is one by one. So my first compound compound A let's say, Well, it doesn't have anything special about it, guys, it has alphas. Good. But these are just normal alfa carbons, so I would expect them to have a peek a about each. Okay, so that's not gonna be the best. Be almost the same exact thing is a Okay, there's really no difference, because I just have carbon deals with Alfa Carbons on both sides. So it's the same thing. Okay, See, See a special CIA's abate anti carbon eel. So I would expect that the hydrogen between those is going to be extraordinary. Lee acidic. It's gonna have a peek A of about 10 case right now. That's my winner. But let's keep going. De anything special about d Actually, D just got worse because notice that everything is an Alfa, okay, but nothing has is in between two carbons perfectly between two. It has like a space, So this one is going to go back to being what the same thing is a Okay, then finally e, what's going on here? Well, guys, I actually have one. Hydrogen, one single hydrogen, that is Alfa 23 carbon heels. Guys, this is gonna be crazy. Acidic. This might have a peek a as low as 6 to 7. Okay, there's going to be the winner for sure. This is the most acidic guys because it conformed ta tumors with all of those carbon yells. All of those conform Enel's. This thing is gonna be going wild. Ta tumors everywhere. Okay, so the answer is e. So obviously E would be a really good molecule, um, to do in an in a late reaction or reaction that requires Todd memorization. Great. So let's keep going.