April 17, 2024, 08:18:19 PM
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Topic: Predicting products of reaction titled “chlorination of disubstituted benzene”  (Read 751 times)

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Offline justswimmingly

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As part of my pre lab assignment I have to write the products/intermediates of the reactions we will be doing. For the first one, 4-bromoacetanilide is dissolved in concentrated HCl and glacial acetic acid, then cooled, and a sodium chlorate solution is added to that. As far as I can tell the purpose of this is to produce Cl2 which reacts with the 4-bromoacetanilide to form 4-bromo-2-chloroacetanilide. This makes sense to me since the title of the experiment is “chlorination of a disubstituted benzene”.

But I’m not clear on the result of the next reaction, where the product from the previous reaction is added to ethanol and concentrated HCl, heated, mixed with hot water, cooled, and then sodium hydroxide is added. So far, the reactions I’ve found in my textbook that seem to apply to this reaction are acid catalyzed and base catalyzed hydrolysis of amides. My guess is that this would produce 4-bromo-2-chloroanilinium chloride, which would react with the NaOH to produce 4-bromo-2-chloroaniline.

However, I don’t feel confident because the title of the lab makes it seem like the point is just to chlorinate the benzene, and the book states that the goal is to see how competition between the two substituents on the original compound plays out. I don’t see how the second reaction as I understand it would aid in that goal, so I’m thinking I might be totally off.

Offline rolnor

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I think you are correct, you hydrolyze the amide

Offline Babcock_Hall

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What amount of time does the reaction with ethanol and hydrochloric acid run?

Offline rolnor

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Yes, maybe just a purification step

Offline justswimmingly

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That step runs for 1 hour, then an additional 10 minutes after the water is added.

Offline rolnor

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I dont think thats enough to hydrolyze the amide

Offline Babcock_Hall

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I agree.  Is it possible that this step decomposes a side product?

Offline rolnor

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Yes, thats probably the case, hard to say what byproduct

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