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Topic: Addition to conjugated alkene  (Read 1873 times)

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Offline shon1802

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Addition to conjugated alkene
« on: December 02, 2016, 08:45:10 AM »
Hi,
I need to write the products of the reaction in which 1 mol Br2 is added to 2,3-dimethylpenta-1,3-diene (see attachment).
There are two double bonds there, and I don't know which bond is more reactive - no carbocations are formed so I can't use Markovnikov's rule. Any ideas?

Offline sjb

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Re: Addition to conjugated alkene
« Reply #1 on: December 02, 2016, 10:52:07 AM »
What sort of reaction is this? Nucleophilic, electrophilic, pericyclic etc?

Offline Enthalpy

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Re: Addition to conjugated alkene
« Reply #2 on: December 02, 2016, 12:54:07 PM »
Is it possible to distinguish the conjugated bonds as if they were independent? In several reports I've seen, the double bond of the product remained where a single bond is conventionally drawn at the reactant, that is, between both conventional double bonds.

Offline spirochete

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Re: Addition to conjugated alkene
« Reply #3 on: December 02, 2016, 02:29:38 PM »
Look in your book for the section on "addition to conjugated dienes". There will be a discussion of 1,2 vs. 1,4 products. With conjugated dienes, it does seem reasonable to propose a carbocation based on the products that sometimes form. This is contrast to regular alkenes, where a halonium ion is always formed.

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