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Topic: Friedel-Crafts Alkylation Question  (Read 8110 times)

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Offline Anooshir

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Friedel-Crafts Alkylation Question
« on: July 17, 2006, 12:44:27 AM »
Friedel-Crafts alkylation of an activated benzene molecule (1,4-dimethoxybenzene) occurs with a tertiary alcohol (t-butyl alcohol) in the presence of sulfuric acid as the Lewis acid catalyst to form 1,4-di-t-butyl-2,5-dimethoxybenzene.  The question is:  Suggest two other compounds that might be used in place of t-butyl alcohol to form 1,4-di-t-butyl-2,5-dimethoxybenzene.  I am having a lot of trouble with this question and am totally stumped; I would greatly appreciate any assistance in answering this question.  Thank you.

Offline AWK

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Re: Friedel-Crafts Alkylation Question
« Reply #1 on: July 17, 2006, 04:47:47 AM »
What about isobutene (2-methylpropene)?
AWK

Offline Dan

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Re: Friedel-Crafts Alkylation Question
« Reply #2 on: July 17, 2006, 07:03:55 AM »
You just need a source of the t butyl cation - so you could change the leaving group...
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Offline Yggdrasil

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Re: Friedel-Crafts Alkylation Question
« Reply #3 on: July 17, 2006, 12:42:05 PM »
Basically the question wants you to know/realize that in F-C alkylations, the reaction between your Lewis acid and your alkyl donor produces a carbocation and that these carbocations will undergo intramolecular rearrangements before reacting with your aromatic molecule.  So, AWK's suggestion is a good one (although Dan's is much simpler).

Offline AWK

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Re: Friedel-Crafts Alkylation Question
« Reply #4 on: July 18, 2006, 07:36:53 AM »
Using isobutene and H2SO4, t-butyl hydrogen sulfate is obtained - hence the leaving group is HSO4- - this is a special case of Dan suggestion
AWK

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