Organic Chemistry

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18. Reactions of Aromatics:EAS and Beyond

Side-Chain Oxidation

We know that the alkyl group directly attached to benzene is known as an alkyl side-chain. Now, regardless of the length of that side-chain, it can be oxidized to benzoic acid using hot KMnO4. What's the kicker? There must be at least one benzylic hydrogen.



Benzylic Oxidation

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in this video, we're going to cover a pretty easy concept called side chain oxidation. So the Al Q group that's attached directly to a benzene is known as the alcohol side chain. Okay, this is a site where special reactions can take place because it's right next to a benzene. Okay. And it turns out that regardless of the length of the alcohol benzene side chain Okay, no matter how long it is, it can always be oxidized just to a Benz OIC acid using hot potassium permanganate or camera four. Okay, so let's look at this reaction really quick. I got the general reaction here we've got in our group can notice that I'm not specifying how long it is. It could be a single saved three, as in Tall Ewing. Or it could be like 100 carbons long and go off the page of your off your screen and onto the wall behind you and around the room. It doesn't matter, guys, how long that our group is hot. Camera four is gonna cleave the entire chain at the Benzel Excite at the Benzel Excite, and it's going to replace it with the car oxalic acid okay, when you have a car was like acid on a benzene ring that specifically called Ben's OIC acid. Right. Cool. Now, one thing that professors might start to get picky about at this point of your course in or go one, we would usually just say came in before and be done with it. Strong oxidizing agent, in order to were typically a little bit more cautious about how we talk about the reaction conditions. So usually it's actually like four things that we right, it's gonna be camera for, then base and heat. And finally, afterwards, you use acidic reaction to basically, you know, to finish off the re agent. Okay, The reaction. Okay, So from now on, when I write came in a four, which will happen more in this course, I'm always gonna be using these regions in this specific order. Okay? And this just has to do with these air the lab conditions that are most favorable to produce an oxidation. Okay, now, there is one exception that you need to know, but it's pretty easy. All it is is this. They're always must be at least one Ben's Ilic hydrogen present for oxygen oxidation. to occur, meaning that it's not enough to just have in our group. I also need to have an h on that. Our group. If I don't have an h, I'm not going to get an oxidation. So you could already start thinking in your mind of what kind of alcohol groups would not give you an H? Well, ones that have lots of carbons in that position. So we're going to do an example with about that. Okay, Now, you might be wondering about the mechanism. Guys, don't worry about the mechanism here. Okay? That's not the point of this chapter. This chapter is not your oxidation reduction chapter. It's your air Metis City chapter. So we're not gonna worry about any mechanism here. And in fact, I never worry about these mechanisms at this point of the course. Okay. Just know to recognize the re agent, know how to draw those four reagents in order. Your professor might be one of those that actually picky about how you draw camera four and then you know what the product is gonna be. So here we are, which is the following alcohol. Benzene would not yield bins. OIC acid in the presence of Hot came in a four. So go ahead and let you guys think about it for a little bit and then I'll come back and answer the question.


Which alkylbenzene would NOT yield benzoic acid, treated with KMnO4

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All right. So we said that regardless of the length of the ark group, it's always gonna turn to a Benz OIC acid. Unless you're missing hydrogen is okay. So essentially three of these have a Benzali hydrogen one does it. A has a hydrogen. See, he has a hydrogen and d actions to hydrogen, but be has none. So be is the answer be would actually display no reaction when reacted with communal four, because it does not have a Benz Ilic hydrogen available toe oxidize. So it's not gonna be able to respond to the oxidizing oxidizing agent. All right. Awesome guy. So, like I said, pretty easy concept. Not much to know. Let's move onto the next one.