Starting with either benzene or toluene, how would you synthesize the following substances? Assu

step 1 All right. Four more synthesis. This time we're allowed to start from benzene or toluene, and we

Starting with either benzene or toluene, how would you...

Key Concepts

Oxidation Reactions

Oxidation processes are often used to transform alkyl side chains into carboxylic acid groups. This reaction is particularly useful in aromatic synthesis when starting from an alkyl-substituted benzene. The ability to oxidize a methyl group to a benzoic acid group provides a route to incorporate a strongly deactivating and meta-directing group, thereby expanding the synthetic options for further substitution reactions.

Functional Group Protection

Certain functional groups, especially those that are highly reactive or strongly activating (like amino groups), may need to be temporarily masked or protected during reaction steps that require harsh conditions, such as nitration or halogenation. This protection helps to prevent unwanted side reactions or overreaction, ensuring that the desired transformation takes place at the correct position on the aromatic ring.

Reaction Order and Strategic Planning

The sequence in which substituents are introduced into an aromatic ring is critical due to the cumulative effects on reactivity and regioselectivity. Early introduction of strongly activating groups can lead to overreaction, whereas deactivating groups can hinder further substitutions. Strategic planning involves determining the optimal sequence of reactions to achieve the desired substitution pattern, balancing the effects of each functional group and sometimes incorporating steps like protective group strategies or oxidation processes.

Electrophilic Aromatic Substitution

This is a fundamental reaction in aromatic chemistry where an electrophile replaces a hydrogen on an aromatic ring. The reaction typically requires a catalyst (like a Lewis acid) and is dictated by the stability of the arenium ion intermediate. Understanding this mechanism is crucial, as most of the synthetic steps in aromatic substitution involve introducing groups such as nitro, bromo, fluoro, or the conversion of alkyl groups via electrophilic aromatic substitution reactions.

Substituent Directing Effects

Substituents already present on an aromatic ring significantly influence where new substituents are introduced during electrophilic aromatic substitution. Activating groups (such as alkyl groups) are ortho/para directing, while deactivating groups (like nitro or carboxylic acids) are meta directing. Knowledge of these directing effects and the relative strengths of substituents in influencing reactivity and regioselectivity is key to planning multi-step syntheses where precise substitution patterns are required.

Transcript

0:00 All right.

00:01 Four more synthesis.

00:02 This time we're allowed to start from benzene or toluene, and we can separate orthopara isomers.

00:09 That's great.

00:10 So with this first example, you'll look at the substituents, right? so you have a methyl group that's para to a nitro group and ortho to a bromode.

00:19 So that's just fine because if you add the methyl group first, that will direct the nitro group, para, and ortho, but you'll isolate away the orthoismar.

00:30 And then you can add the bromine ortho to the methyl group, meta to the nitro group.

00:37 That's perfect.

00:38 So here, just to save myself some trouble, i'm allowed to start from tallywene.

00:42 So i'm going to start from tallywine.

00:44 And if you don't want to, just do a fridylcraft with methyl chloride and aluminum chloride.

00:49 So first we're going to do nitration.

00:52 And the reason why we're doing nitration first is because that will add to the paraposition.

01:02 And then that will encourage that bromine to go to the meta position, meta to the nitro group, or phil to the methyl group.

01:11 So that's awesome.

01:11 I'll use aluminum tribroma.

01:13 I'm trying to diversify my lewis acids here.

01:15 And that will give us two bromo, four nitro, toluene.

01:20 Great.

01:21 One methyl is what that means.

01:24 I feel like this is a little bit of a softball.

01:28 Try nitrobenzine.

01:29 One, a very explosive compound.

01:34 135 trinitrobenzine.

01:35 So obviously we're going to do a nitration.

01:38 Let's do one nitration and then we'll see where we're at.

01:45 Right.

01:46 So i'll give you that one.

01:48 And then any further chemistry is going to be meta to that nitro group.

01:52 So that's going to give us subsistituents here and here.

01:56 Right.

01:57 So if we do two more nitrations, the ring's going to be deactivated.

02:00 It's going to be harder to do those nitrations, but they're going to be regioselective for those two positions.

02:06 So let's do two equivalents.

02:08 Of nitric acid to equivalence of sulfuric acid.

02:12 And let's get those other two on there.

02:14 So once you add the second one here, this final position is meta to both those first two nitro groups.

02:23 So that's perfect.

02:26 All right.

02:26 This one's kind of fun.

02:30 246 tribromo anelin.

02:34 So do you think we have to add the bromines first or the anilin first? so notice that all of the bromines are.

02:41 Either ortho, they're either ortho or para to that amino group...

Please give Ace some feedback