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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.

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18. Reactions of Aromatics:EAS and Beyond

Diazo Retrosynthesis

Ready for some practice on Aromatic synthesis? You probably have done problems similar to this before but now we want to work specifically using diazo replacement reactions

1
concept

Proposing Aromatic Synthesis

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Now we're going to get some practice proposing aromatic synthesis, specifically using die as a replacement reactions. So, as you guys know, a big part of this topic is being able to turn a smaller benzine into a bigger one. Okay? And we must use our knowledge of sequence groups and blocking groups to plan out our synthesis in the correct order. So, guys, you should have already had some practice with this at this point. So I'm gonna leave these up to you completely. Go ahead and try to do this one from scratch with everything you know about Tiozzo on. Then I'll step in and show you guys the answer, so go for it.
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2
example

Synthesize the target molecule

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All right. So we start off with Halloween, and we ended up with I guess M scion. Oh, benzoyl gas it. So a few things going on here? First of all, I need to figure out how to turn a methyl group into a car. Oxalic acid. Hm. Not sure if you guys can help me with that. Also, I need toe add a C N group to the meta position. So at some point, I need to turn this into a meta director. Also, what's the fastest way to add a CNN group? Okay, this isn't the only way to add CNN, but the fast way is gonna be to use dyas because we can't use E Yes, and any other methods gonna take away too long. So Diane's was the way to go. So that means that I should add at some point, I should do a dyas Oh, reaction. But on Lee after this thing is a meta director. So the first reaction I should use is my arm hot potassium permanganate. Okay, so I should do camera four, base heat and acid. Okay. What that's going to give me is a meta director. I'm going to get C o h. Now, from there, I can go ahead. And I could do my dad's association. But I need to first just add something that could even become a dyas. Oh, so that would be a nitro group, right? So I have to do a nutrition. So I'm gonna do h n 03 and sulfuric acid, and that's going to give me a nitro group. Okay. And then from here, just the rest of the reactions take over. So then three, I would do my reduction, which, if you used a different reducing agent, that's exit could be a problem. Actually, that's a good point, guys. This is actually the Onley reducing agent. You're allowed to use S N C L to h 12. The reason is because if you use l. A lithium aluminum hydrated, what's gonna happen? You're going to reduce the car was like acid. Remember that carb oxalic acids react with lithium alone. High dry, right? It's gonna turn it into an alcohol. Or what? If you use, um, catalytic hydrogenation, there's still a chance that it could react. You want to use a chemo selective reduction in this case, which is your Stannis chloride, so I'm gonna put your chemo selective. So you guys remember that? Really? You should get used to using the status chloride, because it's the only one that really select specifically for nitro groups. Okay, so now what that's gonna give me is something like this where I still have my car oxalic acid. But now I have an Anna lean. Now, my next free agent should be my dyas. Oh, okay. That's going to give me a molecule. Looks like this C o h and end to positive. And finally, we're at the end, and I can use my fifth three agent, which is gonna be see you, C n, and it's gonna give me my final product. All right, So the guys, that was a five step synthesis, which is totally normal. That's very common in this section of the text to find 568 steps in theses. But what you'll notice is that it's not that hard, because the pathway once we got to the nitrate in part, it's always gonna be the same reactions over and over. So it's not that bad. Okay, so go ahead and analyze the next question and see if you can come up with the right synthesis.
3
example

Synthesize the target molecule

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Alright, guys. So I think this one might have been a little too hard for you, considering that you just learn how to use Diaz a replacement reactions. But I just want to show you an example of more advanced synthesis that requires pretty much all the different directing effects we've talked about. Okay. Before I begin, let's look at a few interesting things here. First of all, notice that I need to add a chlorine in this position here. Okay? Which is tricky because my end product has a meta director here. This is Metta Director, right. So I'm probably gonna wanna add the chlorine before I turn this into a meta director. Right now, this is currently an O. P. Director, right? So I'm probably gonna wanna add the chlorine before I turn it into a car. Looks like acid. Cool. Awesome. What else? Notice that I also have to add and ohh. Here. Okay. After annoy each year. But this chlorine is metta to it. Okay, so I probably want to have some kind of meta director here before I add that chlorine. Because once that alcohol is there, it's gonna switch it to an O. P. director. All right, so these are just some things to consider. Also noticed that I was able to turn a method into carb oxalic acid, but not a Turk Bugle group. Does that make sense? Yeah. That part actually is pretty easy. Remember that tribunal groups are gonna be immune to Canada. Four, because they don't have any hydrogen socks days. All right, so let's go for it. Our very first step guys is gonna be to put a meta director in this position, okay? And thankfully, I have Ortho pair directors on both sides, so it's pretty easy. I can use h two and H h and 03 and sulfuric acid so I can use the night rations. Okay, I'm gonna try to follow along every step of the way. I'll show you guys what I'm doing. So what I'm going to get here is I'm going to get a nitro and my mother, Okay? Now, at this point, um, I totally could add the chlorine now if I wanted to write because I have a meta director that's gonna push my chlorine to form here. So why don't we try that? Why don't we do the chlorination now, So I'm gonna add f e. Oops. Seal too. Over F E seal three. That's going to give me a molecule. Looks like this. And to And I have a chlorine here. Okay, notice that all of my subsistence were synergistic. So that's perfect. Okay, cool. So, what else? Okay, so now I've got that chlorine in place. I eventually got to turn that nitro group into an alcohol. Do I know how to turn Nitro into a female? It's a lot of steps, but yeah, you have to go through the die as a pathway. Okay, Awesome. Now, on top of that, I need toe end up with a nitro. So I should probably start turning this into, um ah, fennel. And then at that nitro. Later, when I have a North A para director. So we could go ahead and do the next step, which is Let's reduce this nitro. Now, what reducing agent would you guys recommend? If you wanna reduce this, I'm trying to reduce the night Charles nitro so I can get to an Anna lean so that I can do a dyas Oh, replacement reaction. So I definitely should use Stannis chloride. Okay, I definitely need to Santa Clara, because that chlorine could actually be reduced by a strong reducing agent toe hydrogen. So I'm gonna go ahead and you Stannis chloride that's going to give me a molecule. Looks like this. Okay? And then I'm going to make it a dyas. Oh, so I'm gonna use my nitrous acid, and that's gonna make it C l um, Now, this is gonna be end to positive to a beautiful and muscle cool. Okay, so now I'm there's no reason that I can't turn it into the final, especially because the funeral is gonna be an O. P. Director. So it's actually gonna be in my best interest to turn into a female. So the re agents to turn it into a phenol are I mean, technically, I could just use water, right? So I could just use water water with a dyas. Oh, group is going to replace. Let's see if I could fit all this in the screen and turn it into a fetal. Okay, Awesome. So, guys now notice that I still need to add a natural group, okay? And the nitro group would be synergistic to adhere if I was using If I'm looking at this and this group, okay, but these two groups disagree. Okay. Is there anything I can do to get mortgage apps to agree to that location? Actually, yeah. What I could do now is I could do Oops. I could do my reduction, my oxidation step to turn this metal into a meta director so I'll have at least one more synergistic. Um, group. So what I'm gonna do is I'm gonna do six cam. It'll four beasts heats and Assad. Okay. And what that's gonna give me is it's gonna give me a molecule. Looks like this. Chlorine. Ohh! And now C o h. Okay. And now, finally, I'm ready to do my night creation, okay? Because I have pretty much all synergistic groups, except for one. So I'm gonna get a high yield. And I would just use my Sophie Eric, my my nutrition again. So that's going to give me I'm all kill. Looks like this. Okay, guys. So that one was seven steps. Kind of intense. Okay, seven steps is definitely too intense for the level that we were at right now. Okay? Definitely. This should have been like the 10th question that you saw our eighth question. Not the second. But I wanted to show you guys an easy one and a hard one. Just that you guys would see kind of the ways that E A S and Dyas will play together, and you have to use them together. Okay, um, now, keep in mind that some professors actually do ask for seven steps in theses. It just depends on who your professor is and how hard they test. Okay, but hopefully that made sense. Um, let's move on to the next topic.
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