Organic Chemistry

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20. Carboxylic Acid Derivatives:NAS

When you hear "saponification"just know that this is a base-catalyzed hydrolysis of an ester. The mechanism and final product are slightly different. Let's take a look. 




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Hey, guys, in this video, I'm going to teach you about the base catalyzed extra high, jealous reaction or better known as the PSA pontification reaction. So, guys, PSA pontification is just a base catalyzed hydraulic assist oven, Esther. Meaning that if I have an Esther and I expose it toe water and base as a catalyst, I'm gonna hide relies that Esther. Okay, Now, we would expect to get a car books like acid. But if all you have is based present, you're actually gonna yield a car box late and I on. And that makes sense because there would be nothing around two protein ate it. Okay, So in the absence of a pro nation step, you actually should end up with an own negative car, Boxley, or what's also called a car box. Late salt. Okay, because there's the full negative charge. Okay, So just you know, that is kind of like, you know that you should be aware of that. You need the pro nation steptoe, get to the car oxalic acid. And now we're just gonna go through the mechanism. I'm not sure if you've heard me say this before, but in general, guys in organic chemistry. A base catalyzed mechanism is always easier that an acid catalyzed mechanism. So this is actually gonna be a very straightforward mechanism. Okay, let's go ahead and assume that I'm gonna be using. Right. I'm using water and base. I'm just gonna use always negative. Okay, that's my base. And in my first step, I'm going to do a nuclear feel like attack because, you know, this is already strong enough to attack that partial positive. I don't need Thio do a pro nation and draw resonance structure to make that carbon active. It's already active because I got a negatively charged nuclear file. So boom and boom, I'm going to get a Tetra Hydro Intermediate. We've seen this before, so I got own negative about O r. I've got Ohh and I've got my carbon. Okay, awesome. So then we're gonna go ahead and we're going to reform the double bond. We're not gonna protein eight because this is nuclear. Feel like a seal substitution. This is an n A s reaction. Right? So we're going to kick out a leaving group now, which one do we kick out? Do we kick out the O. H or the O. R or the our group and I could kick out the are, But that would be retarded. Okay, Sorry. I shouldn't say the r word. Okay, so anyway, h r o r. Um, well, it really depends on the way you want to draw which direction you're trying to go in. Since I'm trying to go towards hydraulic sis, I kick out the O. R. Okay, so that's gonna give me is a molecule. Looks like this. Now it's Ah, Carl. Oxalic acid started thinking. Oh, I did get a carb oxalic acid, But no, because you're gonna have oh, are negative around now and that are negative. Well, D protein ate it. Okay, so then we're just going to get our car box late as a product, okay? Plus alcohol. That's where it ends. That's the end of the mechanism. Now, if you protein ate it afterwards, then fine. You can get a car. Looks like acid, but you need that protein ation step to get there. Okay, So you guys can see super easy mechanism compared to the acid catalyzed version. So let's move on



I hope you guys enjoyed that super easy mechanism:). Ready for the next topic?