Organic Chemistry

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18. Reactions of Aromatics:EAS and Beyond

EAS:Sequence Groups

Sequence groups are groups that have the ability to alter the sequence of an aromatic synthesis since they have directing effect changes. Let's learn exactly what that means. 


Sequence Groups

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in this video, we're going to discuss the synthetic technique having to do with benzene reactions. That's called sequence groups. So one of the major goals of this chapter is to get you to do organic synthesis. So we're actually gonna be learning how to turn a regular benzine into some much more complicated molecule. Okay? And it has to do with aromatic reactions. In order to accomplish this, you're gonna need to use sequence groups. Okay, sequence groups are defined as groups that have the ability toe alter the sequence of an aromatic synthesis. Okay, due to the fact that they have directing effect changes. Okay, So what I'm looking at is that these air groups that can be easily transformed from one type of director to another. Okay, so these are gonna be groups that in one step in one form, they might be an O p. Director, but then after you transfer, form them, they become a meta director. Why is that important? Because that's gonna allow us to substitute different places of my benzene, depending on which directing effect I choose. So let's look at the first one. I think it will become more clear. So reduction of nitro groups is a major sequence group. Why? Because notice that a nitro group is one of the strongest. What type of director is it? It's a meta director, right? So this is one of the strongest meta directors. We know that nitro groups love toe add towards the meta position, but nitro groups are also very easily reduced. We learned earlier in this chapter that you can use pretty much any reducing agent. But you know, specifically l a lithium alumina hydrate. You could use catalytic hydrogenation. You could use Stannis chloride, and you could even just use iron and HCL. All of these would turn a nitro group into an anally. So what kind of directing of directing group is an anally nor NH two guys we know this is one of the most powerful O P directors. Okay, so this is what we would consider a sequence group because the fact that this transformation will determine where do I add my next group? Where do I add my next re agent? So, for example, if I had reacted another e a s mechanism on the first molecule, I would get a meta substitue in if I added on the second one, I get most likely a pair of substantial in right, So it's definitely gonna be important that we know exactly when we're gonna try to react with the secondary and tertiary re agents. Okay, let's move on to another really important sequence group, and that's a Clements introduction. So Clements introduction is going to turn basically in a social group into an alcohol group. But let's look at the directing effects of that in a sealed group. Has a partial positive at the carbon, so we know that's gonna be a pretty good meta director after we reduce and we turn it into hydrogen. What type of director is in our group? Guys? It's an O. P. Director, so this would be another example of a sequence group. It's a group that you have to think about the sequence of the region's before you actually react them, because if you want a Met a sub situate you direct it as an A seal if you want or Thorpe era, you direct it as an alcohol. Okay, here's the last one that is really one of the most common ones, and that is the side chain oxidation. So remember that we talked about how a side chain of any length a carbon side chain of any length can be can be oxidized by potassium permanganate into Ben's OIC acid. Well, this happens to also be a sequence group, because remember in our group has what kind of directing effects It's Ortho Pera. After I oxidized that side chain, it's now going to become ah, pretty strong meta director. Right? So this would also be a sequence group because I have to determine what to do. Want to add that second re agent depending on whether I wanted Ortho Pere or whether one at meta Now remember, guys, there was an exception with the side chain oxidation, which was that if there are absolutely no h is on that Benzali position, then it won't work. So obviously I'm talking about situations where it would work if it would work. If it would oxidize, then that is a sequence group. Okay, awesome. So this is the information that we're gonna take into our questions about organic synthesis because we're gonna need to know. When do you add that second re agent? Okay, so let's move on to the next topic.

1. Reduction of Nitro Groups


2. Clemmenson Reduction


3. Side-Chain Oxidation