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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.

20. Carboxylic Acid Derivatives:NAS

Decarboxylation Mechanism

Lets say you want to get rid of a carboxylic acid. Is it possible? Yes, but under certain circumstances. Let's see when that is. 

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General Mechanism

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Hey, guys, In this video, we're gonna talk about an extremely important way to get rid of carbon oxalic acids. And that's called Dhi Qar box elation. So, guys, Dhi Qar box elation is gonna be a very important reaction for the rest of origo. So it's really important that you understand how to do it now on the way that it works is that Ah Beta Carbonell carb oxalic acid Can d car Boxley in the presence of heat. Okay, on what this does is it produces C 02 gas as a by product. It evolves. Okay, out of the out of the material. Okay. Now what a beta Carbonell car oxalic acid is is just that you have some kind of carbon eel data to your car. Looks like acid. Okay. When you heat that up, what's gonna wind up happening is that you literally cleave the entire car oxalic acid off, and it becomes co two gas leaving on Lee the Carbonell portion behind. Okay, Obviously we need to get to the mechanism for this because it doesn't really make sense just drawn like that. So let's do the mechanism Now, guys, for this mechanism, it's gonna make a lot more sense if you do one thing. Okay, if you rotate, the bonds were gonna rotate this bond up when I draw it, because it's gonna make a lot more sense of the mechanism. So I'm actually gonna draw my oh, each facing like this and my carbon kneel down. But this is still the same exact molecule. I just rotated it, okay? And you should, too. So when I draw this mechanism, it's actually a series of four arrows, and there's no right place to start or no right place to end it all. It's all concerted, but I like to start from the oxygen grabbing the H because that's kind of like an easy place to remember for me. So I would start with the O grabbing this h. Okay, so it's gonna start off like that. Now, if I make a bond, have to break a bond because you can't have too. So now this single bond is gonna give its electrons and become a pie bond between that carbon and that. Oh, well, now that carbon has four bonds, instead of breaking the bond to the carbon, Neil, though I'm actually just gonna break the single bond to the carbon completely notice what this is going to do is it's gonna release. Might see with two O's on it. Because now there is no single bond connecting it to the alcohol group. Yes, the alcohol group. Finally, once I make that bond, I have to break this bond. And there you go. Those were the four arrows we wind up getting. This is a heat mediated reaction. I wind up getting something. Looks like this are with an O. H with a double bond. And I'm gonna get C Oh, oh, Co two. Okay, so now it makes sense why I get the CO two gas, Okay? And it should even make sense. Why the carcass look as it's gone, what might be a little confusing for you is that I told you that you get ah, carbon Neil from this right. And right now I have an alcohol that doesn't seem to make sense. But guys, you This is something that we're going to talk about a lot more if you haven't talked about it yet. But there's something special about vinyl alcohol's. Does anyone remember what's special about vinyl alcohol's guys. They undergo this completely separate special process called Todd Memorization taught Umer ization. Okay, Now, if you want more information on Todd Memorization, I have an entire video for that. There's an entire section of your textbook dedicated to Todd memorization and Enel chemistry. This is called an anal. Okay, Enel or immolate chemistry is a huge deal. So you know you're going to get there if you haven't yet. Okay. But the whole point being that when you taught, memorize what you do is you switch the locations of a dope on and a hydrogen. So what? This actually comes after Todd memorization is this This is the key toe form. Okay, so you wind up getting the key tone. Just take my word for it. Um, that it taught him arises, and then you're fine. Okay. Awesome. So what I want you guys to do is for the next example. Go ahead and predict what the product would look like. I know it's a big, complicated molecule. Predict it, and then I'll explain what's going on

Mechanism:

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Predict the correct structure

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All right, So before you say anything, we're just going to draw the product, and then we will discuss. So that's the annoying part. Just drawing this whole thing, right? So just bear with me. Follow along, okay? We're getting close. So I've got this chain, and that's it. Okay, notice that when I d. Card Boxley, I'm going to get rid of my car. Looks like acid. Okay, I'm gonna need heat to do that. So, guys, does anyone know what this molecule is? Okay, so this molecules called Tetra Hydro kanna been Oliech acid. Okay. Or T h c A for short. This molecules called Tetra Hydro can of it all. Hmm. I met. I'm gonna grow with that tattoo one time. Most awesome, because it's organic chemistry. Alright, guys. So what is this? THC is the active ingredient in marijuana. Okay, so this is the good stuff, right? So it turns out that what we just did was a dick. Our box elation reaction That actually happens in real life. Obviously not with you, because it's illegal. At least in my state, it's illegal still, but where you are, um, we'll see what state law says. Tetro hydro cannibal Anolik acid de car box lates at about 120 degrees to produce the active form of THC. THC A is an inactive form of the drug. So in order for the drug actually worked actually do what it's supposed to do. It's gonna need to de car box late first, which is why they actually smoke it, right? You smoke it to dick, our box late it to activate it. OK, eso. Anyway, I just thought that that was an interesting application. There's probably the most famous application of D card box elation in the real world, but it happens all the time in all kinds of organic reactions. So good for you to know. I know you're not gonna forget it now, so let's move on to the next video.
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Problem

Provide the mechanism for the following reaction.

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Problem

Which carbonyl group will undergo decarboxylation most readily? 

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