Curtius Rearrangement

Hey, guys, In this video, we're gonna talk about a really important synthetic pathway called the courteous rearrangement. So this reaction does go by another name. It's also called the reduction of a Seal, as I'd and that name really describe what's going on here in a sealed as I'd is ah, functional group that has a carbon eel in our group and then n three on one side. That's an aside. Okay, well, if you can reduce this molecule and get the carbon oil to come off, we're gonna wind up getting is we're gonna wind up getting a primary. I mean, now, this is going to require a really interesting rearrangement for that to take place. Okay, Now there's only to re agents in this reaction. There's heat on there's water, so you might think that it's a really easy mechanism, but actually, it's really strange because of the fact that things air atoms were rearranging, and we're gonna have a reactive intermediate called a night train that isn't really commonly seen in or go. So we're gonna definitely, you know, make sure to handle that in the mechanism part. So what are the two steps? The first step is heat. He is going to drive the rearrangement of this molecule here into isocyanate. Okay, Now is a science is its own, its own topic with inorganic chemistry. There are a lot of reactions that we can do with is assigning. But for right now, this is just gonna be the middle structure that we use the intermediate structure that we then react with again to get our primary at me. What's our second step? Our second step is addition of water to that isocyanate that's going to result in a D card box. Elation, reaction, and it's gonna liberate to gas is at the end. It's gonna liberate CO two gas, Okay, because D card box elation reactions always liberates co two gas, and we're also gonna liberate into gas from the decomposition of the A C. L aside in the first step. Okay, now I have mentioned a few terms here, for example, D card box elation. That's a mechanism that I teach in a separate video. So if you want to know more about what a D card box elation reaction is, you can always just type it into the clutch search bar, and you'll find that video. Alright, so that being said, let's go ahead and just dive into this mechanism and see what it's all about. So I already showed you guys, what a seal. As it looks like when you draw it out in bond line structure, this is what you're gonna get. Okay, that's the most common way that it's represented. It's, uh, end the one end on one end and with the formal charges accordingly. But guys, this a side has a resonance structure and that residents structure has to be taken to account. That resident structure would be that the negative charge could make a triple bond that making that would already have three bonds on one side. That means I only need one more bond on the other, or I'd be violating the octet. So if I make this bond, I'm gonna break this bond and form a lone pair on that nitrogen. That means that the resident structure on the other side looks something like this. I've got a triple bond here, a negative charge here because I added an extra lone pair and I still have a positive in the middle because it still has four bonds. Nothing changed for that middle nitrogen. Now, what's interesting here, guys, is that usually these residents structures, you know, both exists. They're both averaging into the hybrid. But in the presence of heat, one of these resident structures is going to influence the character of the molecule more than the other. The reason is because we can get a decomposition reaction. Heat is gonna make this decomposed. Okay? And the reason is because this resident structure of the second one looks a whole lot like end to gas and to gas is just n triple bond end, and it composes 78% of the atmosphere. Okay, so if 78% of the atmospheres and two gaps, do you think it's stable or unstable? It's highly stable, guys. I mean, you're breathing it in constantly. It's not reacting with you, is it? Um, they're not too much. Um, there's a very stable entity. And if you could become into gas, you're like in chemical nirvana, right? That's like the best thing you could do. Look at this resonance structure. It's one bond away from being into gas. So in heat where you're gonna get as a decomposition reaction where this these electrons pick up and leave us alone. Pair. And what you wind up getting is now your end with just two lone pairs and nothing else. Bar plus your end to gas. Okay, now this molecule that I drew as a product, it's really an intermediate because it has the right number of valence electrons. Remember that nitrogen wants toe have five. It has five. But this is highly reactive because it's not filling its octet. This nitrogen on Lee has six octet electrons. If you were to count, Lone pair is to lone pairs to bond is too. That's six. We need eight. So this is a very reactive intermediate called a night train. And it turns out, guys, this night train is gonna want to rearrange. This is the Curtis rearrangement part. So we're going to get Is that the our group? The electrons from the our group actually attached to the end, a lone pair comes down and forms a double bond. This is going to give us. So this is just gonna be a rearrangement, okay? And what we wind up getting is or is society as a product? So I'm gonna have Oh, double bond. See? Double bond n with now on our group coming off of it. And this is a molecule called is assigning which, as I alluded to earlier, is actually really important molecule in organic chemistry. There's a lot of different edition reactions we could do to this, but for this mechanism, we're only going to do one. And that's gonna be the addition of water. Okay, so you could end this here if all you did was he added heat to in a so as you get isocyanate and you'd be done. But we want to get a primary. Amine. Essentially, we wanna liberate this part. All we want is the N R component. We don't want the carbon. We don't want the Oh, how can we get rid of that if we add water? So in my second step, I add water. Can you guys predict which Adam the water will be most attracted to in a nuclear filic attack? What do you think? You got it? We're gonna attack the carbon, carbon, carbon guys and we're gonna push the electrons down to the end. Came What this is going to give us is a molecule and it looks like this O h and are, And eventually this is going to get in each okay, because it's gonna form a negative charge. And it's gonna protein eight. Okay, so this is gonna This is called carbonic acid. Okay? Carbon make acid. And what's special about carbonic acid guys is that it is very unstable. It's not a stable molecule, so it can spontaneously dehar Boxley. Now again, for more on the mechanism on D card box elation. Search that topic individually, but we'll just draw it as it relates to this molecule here. This is gonna be our D card box elation. So what we're gonna do, guys? Is that the nitrogen? Let me just let me actually draw this age sticking out, so it's gonna be easier. This nitrogen grabs the h. Okay, make a bond break a bond. We're gonna take the electrons from this single bond and donate them to the bond between the in the sea. And now that that carbon has four bonds the carbon, the carbon or carbon, we're going to use these electrons to make a lone pair on the end. So it's a weird reaction, but guys noticed what you get at the end, where you're gonna get is now a nitrogen within our group with how maney ages to you've got the original h and we've got the new h that we grabbed. What else do we have? Well, we also have a carbon with now a double bond. Oh, and a double bond. Oh, do you guys know what that is? Guys? The product of a D card box elation is always C 02 gas. So we just created two different gasses. One of them is a greenhouse gas. Oh, no. Hurting the environment. Hopefully, it's, you know, we're keeping it in the lab, though. So, guys, So this is really interesting. We've just made co two gas. We've made n two gas here and here, but most importantly, and what your professors were most interested in is that we made a primary amine. Okay, that primary mean also lost a carbon. So there's gonna be an interesting synthetic reaction that we use when we're trying to get in a mean and we're trying to lose a carbon. I'll show you guys why you would want to do in a second. There's a really great reaction to use. It looks complicated, but it's actually used more often than you think in organic chemistry. So that being said, that's the whole mechanism. I hope that made sense. Let's go ahead and look down at this question. Now, this question does draw from our Air Metis City chapter electrical like aromatic substitution. But that being said, if you have covered those chapters already, go ahead and try to remember Brush up on those reactions, see how you could perform this synthesis of making Anna lean. Basically, what I'm trying to do here is I'm trying to make an a lien, and we've never learned in E. A s technique to make aniline before. So I want you to think about how you could use the qwerty ist rearrangement to make an A lien and then we will I'll show you the answer, so go for it.

Alright guys. So maybe you didn't know it, and that's okay. But what I do want to emphasize here is that this pathway that I'm showing you is one of the more important pathways for aromatic synthesis. And it's one of the fastest ways that you could make an elite. Because if you recall, I've never taught you in E a s mechanism for Angeline. So we have to get creative when we want to make it. So the first thing you do is you add in our group. So that was already done for you. We already have in our group there. So if you wanted to add in our group hopefully you could remember some reactions that you could use to add our groups. For example Friedel crafts operation. Okay, But now the our group is there. What could we do? What? We want to turn this into a a seal aside to rearrange. So the first step to doing that would be a carb oxalic acid. Let's go ahead and do a side chain oxidation with communal four. Now, I'm already noticing I'm gonna run out of room on this box because camera before you could write it. But some professors want to see every single re agent, so it's right that out. It's gonna be in base with heat slash over acid. Okay, so que metaphor is the short way to put it. But now I just included all the re agents. So what that's gonna do, guys, is that's going toe ad. I'm not gonna draw every single structure. I'll just draw it one at a time. That's gonna add a carb oxalic acid here. Remember that you always pretty much can oxidize any side chain to a car oxalic acid as long as it has at least one hydrogen on it, Which it did. Perfect. So the second step would be, Let's figure out a way to make this in a sealed aside, we have to put an end three. So the next step would be to use eso seal too. Okay. S O. C. L two is a very common re agent to turn Carlos Ilich acids in tow. Acid chlorides. Okay, so now I've just kind of heightened the reactivity of my carb oxalic acid derivative. This reaction, the next two reactions that you're gonna find come mostly from your carb oxalic acid derivative section off organic chemistry. And if you want to brush up on any of these reactions, feel free to go look through there. If anything, Even if you haven't learned these reactions yet, just know this pathway because this is the way that you're usually going to use a courteous. So now I've got the SL Co two. That's a great leaving that coins a great leaving group so I can react it with n A and three. Okay, what that's going to do is you got n three negative, right? It's just gonna do a nuclear feel like a seal substitution. Now, that's not the correct mechanism. There should be a Tetra Hydro intermediate. I know, but just letting you know that's the abridged mechanism. Eventually the chlorine gets kicked out and I get something that now looks like this. And three. So, guys, now that you have n three, what could we use as our last free agent to form Annaly? Guys, we can use heat and water, so I'm gonna put heat and water. How so? How does that make Annaly? Well, guys, remember what's gonna happen. What's gonna happen is that two of these nitrogen, They're gonna leave. So you're just gonna instead of being end three, it's gonna rearrange just to end right Then you're our group is gonna pick up and attached to the end. Remember, you're gonna get a double bond all that stuff. Eventually you're gonna d card box, like taking the carbon off. So are you gonna have left is the nitrogen attached to the benzene ring, which is an elite. Okay, so this is a very common way to make an a lean in organic chemistry to maybe not so much in the lap but synthetically. You'll see this pathway come up sometimes. Um, just to help you guys out in terms of a shortcut, I'm not sure if you guys have noticed yet. There is one. Which is that if you ever want to predict what the Amine is gonna look like at the end, all you have to do is just look at your Aysal as I take your art group, take your our group and add the n h two to it. That's all I have to do. So in this case, noticed that my our group was a benzene ring. So in this case, All I would do is I would take my benzene ring and I would add an intro to to it. And I would say that's gonna be a product. Okay, now, obviously that mechanistic Lee, that's terrible. But as a shortcut, if you're you know, you're all your exams air time. So you have to be shrewd about how you use your time. This is a great shortcut that you can use. You can just say the courteous rearrangement just adds an N H to tow whatever argued by already had. Okay, awesome guys. So I hope that made sense. I hope you found this video helpful. Let's go ahead and move on to the next video.