Propose a synthetic route for the following transformation.

Question

transformation reaction

Accepted Answer

everyone. So here in this practice question, it says, propose a synthetic route for the following transformation. Now this synthesis question is a bit challenging, but here's what we need to understand. What type of functional group am I making as a product? That's right. We're making an ester. Right? We have a carbonyl connected to an oxygen connected to a carbon. So, we're making an ester. We know that esters can be created through reactions of what we learned with carboxylic acid derivatives. Typically, to make an ester, we have a carboxylic acid plus an alcohol by Fischer's Derification. This will help make an ester. So, this will help guide us on what to do. Right? So, somehow, I need to have an alcohol on Benzene and somehow I need to create a carboxylic acid in some way. Alright. So remember, if we think backwards in terms of this and we cut this bond, what we had at one point is we had this alcohol and we had this carboxylic acid. And due to loss of water, they closed to make this cyclic ester. Alright. So this tells me, okay, I need to have this is CH 2. I need to get an o h onto this, but at the same time, I need to have a carboxylic acid here that's ortho to it. Alright. So let's start out with our toluene or methylbenzene. K. Here goes methylbenzene here. Remember it is an ortho para director, so the incoming group would have to go para. If we're looking here we have an alcohol group and a carboxylic acid group that are ortho to each other. We can't do that unless we block the para position. Typically, to block the para position we do sulfonation. So we do s l 3h s l 3 over h two s o four, so sulfonation. That's going to block the pair position. Next, remember we can create a carboxylic acid if we can somehow get a nitrile group onto benzene and then do the process of reactions of nitriles, we could convert that into a carboxylic acid. Right. So what we're gonna do next is we're gonna do nitration. The methyl grouping ortho para director says the nitro group needs to go ortho to it. Next, we're gonna do desulfonation, so h three o plus. That'll remove the sulfonic acid group. So now we have this. Now if we take a look, we need to get an alcohol. We need to get an o h group on top on this carbon here. We can't do it directly. What we need to do next is we need to do n b s. Remember, n b s here will replace 1 benzylic hydrogen with a bromine. And now that we have that, it's a primary alkyl halide, primary benzylic alkyl halide. I can do s s n 2, so n a positive o h minus. This will come in, hit this carbon and kick out the b r. And just like that, we have our alcohol. What we do need to do now is we need to convert this n o two group and change it somehow into a carboxylic acid. Now we can do this by reducing this n o two group next into an n h two, so tin over h c Now I have an NH 2. Next, I can do Sodium Nitrite slash HCl over our Cenmayer reaction which has copper 1 cyanide. Remember, the top one would change my n h two into a diazonium salt and then CUCN would change that diazonium salt into a nitrile group. So now I have my Nitrile group here. And this is what we can do next. We would do H30 plus H30 plus will have 2 desired effects. First, it'll convert my C N group into a carboxylic acid. And then secondly, it can serve as a catalyst to help the alcohol and the carboxylic react together in order to make my ester. And remember, what's gonna happen here is we're gonna lose water. Losing that water is what gives us our final answer at the end. K. So you have this final product up here, and I am a horrible, horrible drawer. There we go. So this would be our final answer. Now, again, we would go we can go straight from here, do h three zero plus, and get to this product here. I'm only showing this middle part here to show you how the heck this thing become this thing. Again, the h three zero plus has two effects. It's changing our Nitrile into carboxylic acid and it's acting as a catalyst to help us do the esterification or esterification reaction where the alcohol and the carboxylic acid will react in order to make my ester at the end. Alright. So again, as you can see, this is a pretty long synthesis but if you can follow along each of the steps, you'll see that it makes sense that this is the best approach to make our desired product. Typically, when it comes to synthesis questions, just look and see what kind of product do you make at the end. What's the functional group? That's a key to understanding the path to take. Making an ester, although it looks different from a typical ester because it's cyclic, we know that a common way to make an ester is through the Fischer esterification process. That tells me, Hey, I need to have an alcohol somehow and I need to have a carboxylic acid as well. Once I can figure that out, they can react together to make my final ester, right? So keep that in mind when looking at different types of synthesis questions.

Struggling with Organic Chemistry?

Propose a synthetic route for the following transformation.

Watch next

Review of Nitriles practice set