Where will halogenation take place?

Asked May 11 '20 at 12:09

Active May 11 '21 at 12:03

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In the following halogenation reaction:

At which position will halogenation take place?

It is obvious that the halogenation will take place at a 3° Carbon atom (the rates of halogenation for 3°,2°,1° atoms follow the ratio 1600:82:1 or thereabouts). The question is which 3° atom? I labeled the atoms as shown:

I believe that halogenation will take place at A because the cyclopropyl ring can stabilize the free radical formed at A better than the 6-membered ring. A similar question that deals with carbocations is here, which shows the stability of the cyclopropylmethyl carbocation. Can a similar logic also be applied to free radicals? Please confirm.

asked May 11 '20 at 12:09

Aniruddha Deb

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What do you know about the stability of cyclopropyl radicals? – Waylander May 11 '20 at 12:24
@Waylander they are more stable than 3° radicals – Aniruddha Deb May 11 '20 at 13:03
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And they ring open – Waylander May 11 '20 at 13:15
@Waylander I did not know that. – Aniruddha Deb May 11 '20 at 13:18
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I'll try to answer this on my own using the first page of this as reference: https://pubs.rsc.org/en/content/articlelanding/1993/cs/cs9932200347/unauth#!divAbstract – Aniruddha Deb May 11 '20 at 13:19
Cyclopropyl methyl radical is different from cyclopropyl radical. Why one C-H bond and not the other? Do bond angles play some role? – user55119 Sep 13 '20 at 11:58

Where will halogenation take place?

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