How would you synthesize the following compounds from benzene? Assume that ortho and para isomer

step 1 All right, here lies another synthesis problem. We could only start from benzene this time, and

How would you synthesize the following compounds from...

Key Concepts

Functional Group Interconversion

Functional group interconversion involves transforming one functional group into another to achieve a target molecule. In aromatic synthesis, initial electrophilic substitutions might introduce a functional group that can later be modified—through oxidation, reduction, or other chemical reactions—to yield the desired compound.

Substituent Directing Effects

Substituent directing effects refer to the way existing functional groups on an aromatic ring influence the position of new electrophilic substitutions. Groups can be activating or deactivating and direct incoming substituents to either the ortho/para positions or the meta position, which is crucial for planning regioselective synthesis paths.

Electrophilic Aromatic Substitution

This is a class of reactions where an electrophile replaces a hydrogen atom on an aromatic ring such as benzene. It forms the basis for many aromatic synthesis processes and is pivotal in introducing new functional groups onto the benzene ring while maintaining aromaticity.

Friedel-Crafts Reactions

Friedel-Crafts reactions, which include alkylation and acylation, are specific types of electrophilic aromatic substitutions. They are commonly used to introduce alkyl or acyl groups onto benzene, acting as key strategies for building more complex aromatic compounds through the formation of carbon-carbon bonds.

Transcript

00:01 All right, here lies another synthesis problem.

00:04 We could only start from benzene this time, and totally we could separate ortho and paracysmers.

00:11 So now we're working with these tri -substituted benzene.

00:15 So by now, if you've done the other 67 questions in this chapter, you might be a little more proficient in trying to figure out these puzzles, right? so recognizing relationships between substituents.

00:31 So starting from benzene, i totally didn't leave myself in the room here.

00:37 Right.

00:37 So just looking at the relationship, it looks like we're going to have to do a bromination, a nitration, and a friedelcraft's alkalation.

00:45 So looking at the relationship with respect to the methyl group, you have an ortho -bromine and a para -nitro group.

00:52 And that's good because ortho and para are the positions that methamphetamine.

00:57 Methyl groups direct the next electrophilic aromatic substitution towards.

01:02 And it looks like we're probably going to have to add the methyl group before we add a nitro group because we can't do frito crafts with a deactivated benzene ring.

01:12 So i think this problem works really well, pretty much three steps.

01:16 You can just add each reagent sequentially if you add the methyl group first.

01:20 So i'm going to go ahead and do methyl chloride and aluminum chloride.

01:27 As my first step to make tonyene.

01:30 Again, you'll probably make p -zylene.

01:32 You'll probably make that dimethyl polysubstuted equivalent, but we're allowed to separate those.

01:39 And now i think nitration is the best way to go because the bromine is meta to the nitro groups.

01:46 Now you're going to have directing power from the methyl group to the ortho position.

01:53 The bromine would want to be ortho to the methyl group and meta to the nitroids.

01:57 Nitro group and that's exactly where the the that's exactly where that bromine is going to be directed to if we nitrate i'm just going to move the arrow over so i have enough room to write a nitro group here and 2 oh right so now we have this nitro taliumene um that we can then do bromination with um i'll use aluminum bromide and right to the the method the meta sorry oh my god i'm so flustered um the methyl group is going to direct ortho the power position's already taken up and then a nitro group is going to direct meta so that's fair game for making that bromonitro talewine this next one's kind of tricky right so you have this it's an isobutal alcohol group on the same ring as a chlorine and a sulfonic acid so if you're going to do some kind of friedel crafts.

03:02 Remember, you can't do that to a deactivated benzene ring.

03:05 So you have to add that alcohol group before you do the sulfination.

03:11 So the way that i did this was, i actually did this problem backwards.

03:18 So i recognize that the sulfonation can't happen first, right? as i just said, you can't do freud crafts.

03:26 And if you add the chlorine first, you'll be able to add the you'll be able to sulfinate at the paraposition because chlorine is an ortho -para -director, but then your regiochemistry for adding the alcohol group is screwed up, plus you can't do frito crafts with a deactivated ring.

03:46 So i felt like you can't add the, you have to add the alcohol group first.

03:53 And then by doing that, if you added the alcohol group as an alcohol group, it's going to be an ortho -paradirector.

04:02 Right.

04:02 So then if you try to do sulfination, that will be in the ortho position.

04:07 But then when you try to add the final chlorine, it's going to be more strongly directed to a metaposition by the sulf, the sulfonic acid, because that's a stronger deactivator than the alcohol group is an activator...

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