18. Reactions of Aromatics:EAS and Beyond
Acylation of Aniline
Since aniline is strongly activated, unwanted reactions can occur. However, we're in luck because we can avoid this issue. Let's see how.
Protection of Aniline Derivatives
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in this video, we're gonna talk about the challenges off doing E s reactions on Anna lean because it's the most activated benzene. So strongly activated rings like Angeline. Remember I told you guys that NH two is the most activating group, Okay, Unfortunately, even though it's activating so it wants to react, it's so active that it opens up the ring toe unwanted reactions. Okay, so let's say that you have your channeling and you're trying to do a nitrate in on it. So you've got your nitric acid. You've got your sulfuric acid. Everything's going great. You're excited for this reaction. You're thinking you're going to get a mix of Pera and Ortho products because remember, that alien is an O. P. Director, so we wouldn't expect much meta director and you're thinking this is gonna be great. Okay, But we've got a problem. This aniline is so active that we're going to get some Polly substitution going on, meaning multiple reactions taking place. We may not get the desired product that we want. Okay, so actually, this is not gonna work. Unfortunately, even though according to everything we've learned so far, there should be a perfect reaction But it turns out like I said, Angeline is just too reactive. We're gonna need to do something called protection. We're gonna need to protect the Anna lean before we can keep reacting with it. So how do we avoid this? Well, what we do is we do something called Ah, see dilation. Okay. Assimilation is a reversible reaction that makes the Angeline less reactive. Still activating, but less reactive so that we could get a single product or the one that we're desire ing the most. Okay, so this is the way that a simulation works. Assimilation takes an acid chloride okay with some kind of base. Okay. Any kind of base, because it's a base catalyzed mechanism. In this case, I'm using parodying. Purity is a very popular base in this chapter. It's aromatic itself, But you could use any other base. Okay? It doesn't have to be Angeline Okay on. And what that's going to do is it's going to react with my Anna lean toe. Add the acetyl group, okay? And the Seattle group is a two carbon, um, a social group, and you're gonna add the acetyl group to my nitrogen. Okay, now, this is a mechanism that at this point, you don't need to fully understand. I'm not gonna fully teach, but you can imagine that it goes something like this. This is like the abbreviated mechanism that are nitrogen would attack the carbon and kick out the chlorine. Okay, now, that's not right. Don't show that to you, Professor. But then again, your professor is not gonna ask for this mechanism at this stage of the course. Okay, so now we've got our assimilated or protected A mean, Okay, now, what did we learn about this group? Well, this nitrogen is still donating. It's still activating because it has a lone pair. But it now has that carbon Neil. That's next to it. That makes it slightly less activating. Instead of being strongly activating, that was just moderately activated. How does that help? Well, because now that it's moderately activated, I can run my reaction on it. So I could then at this point now, I could do my nitric acid over my sulfuric acid and I could get my reaction. So now, at this point, I could get it. Let's say that it adds mostly peril, which it would at this point because of hysterics. It's gonna add mostly Pera. And what you would wind up getting is now a nitrogen. A natural group in that position. Okay, Now, the cool thing about this assimilation guys, is that we don't want to keep the aceto group. We're just doing that so that we can get a moderately activated ring. Now that we've assimilated, we can easily remove it with base base is gonna hide. Relies this thing off. Okay, it's called. I'm gonna actually it that down its hydraulic sis. Okay, it's gonna hide realize that a Seattle group group off and we're gonna wind up getting the Angeline again. But now with my substitue int that I wanted Okay, so it's a little bit annoying, guys. But now, for the rest of this course, anytime you're working with Angeline, you're always gonna have to think protection. You have to protect Angeline before you can react with it. Because what's gonna happen is you're gonna get unwanted reactions. Your professor isn't gonna be happy. Okay, so we're always gonna do this assimilation process. Whenever we were working with Angeline. Alright. So that said we have a problem down here where I want you guys to synthesize this compound. Okay, so go ahead and, um synthesize the target compound using the four re agents. So, as you can see, we have four trying to think about everything we've learned so far. This is a cumulative react curative question based on several things that we've already learned. So go ahead and try to figure out what those four re agents are. And then I'll come back and I'll answer it for you guys.
To avoid this, we can reversibly acetylate (protect) the amino group to make it moderately activating.
Synthesize the target molecule
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Alright, guys. So this is a very typical multi step synthesis problem that you would face in this chapter. Okay? And there's a lot going on. The first thing that we notice is that first of all, none of the substitutes on the first molecule are on the second. So either have to figure out how to remove them or how to transform them. In the case of the Nitro, do we know any ways to transform Natural Group into an amino group? Hell, yeah, we do. Okay, so we'll come back to that in a second, Okay? Now, we also are adding a chlorine. Do we now have the tools to add chlorine toe? A benzene ring? Yep. That's s okay. So you might be wondering, Why does this take four steps? Well, if you're getting an a lien, if you're you're working with aniline, you're gonna have to protect it, right? So let's start off with the beginning. What do you think the first re agent should be like? For example, can I can my first re agent be an E a s chlorination? Should I do that first? No, Guys, you can't, because if you chlorinate right Now you have a meta director. You're gonna wind up getting a chlorine here. Is that what we want? No. We need to transform it to a Opie director first, meaning that I have to reduce it first. Now, you could use any other reducing agents that I've mentioned in the past, so all of them will be correct. I'm gonna use the status chloride. Okay, I told you is that's my personal favorite. So I've got my 10 to chloride. I'm sorry, s N c l two and water. Okay. What that's gonna give me is my annalee, and so I'm just gonna draw it on the side. Okay, so now I've got my Angeline in place. Can I just do a coronation? No, I can't. Before this topic, you would have, and you would have thought you're doing great. But now, because of this topic, we know that you need to asili or protect the amino group before we can keep reacting with it. So we're gonna do is we're gonna add See, I'm sorry. Yes, it's sure. Ch three c o c l over period ing. Okay. And what that's going to give us is now molecule looks like this where my nitrogen has in a Seattle group on it. Okay. Why? No. Awesome. So now that we've got that now I can do my reaction. Now, I can actually do my s reaction. And what's that gonna be? My actual s reaction is all too over f e c l three. So let's go ahead and add that here. Seal too. F e c l three. That's gonna go ahead and give me a I'm just gonna draw it over here, because that's right where my head is. I move that that's going to give me a benzene ring that now looks like this. I've still got my assimilated or my protected nitrogen. But now I've got a chlorine in the pair of position. Why did it add Pera guys? Because that a Seattle group is hysterically bulky. It's definitely gonna favor of the pair. Mostly. Okay. And now, when I want to finally get to my end product, all I have to do is use in a way, which or any type of base to do my hydraulics, iss and regenerate the original aniline. Alright, guys. So this is a very typical type of multi step synthesis that you could be responsible on your foot on your exam or on your online homework, or even just in your textbook homework. Okay, And now that we understand this idea of protecting and leans, it's something that you can't forget. Okay, awesome, guys, let's move on to the next topic.