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In the following question:

question

First the Cl will eliminate forming a double bond. After that the H+ attacks which has two possibilities, either the oxygen or the double bond. If it attacks the oxygen then the following carbocation will form:

carbocation

which is resonance stabilised, tertiary, allylic carbocation hence highly stable. Now this carbocation attacks the benzene ring to form a 4 membered ring? Why can't this product be major?

Some of the reasons I believe are:

  1. The H+ attacks the double bond as it's more nucleophilic than lone pair of oxygen.
  2. Four membered ring is strained so it's a minor product.

I am not sure which one is true. The answer given in this book is 4th option.

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8
  • $\begingroup$ Of course it's too strained - isn't happening when 6-membered is perfectly fine. $\endgroup$
    – Mithoron
    May 25 at 16:52
  • $\begingroup$ Is it because of this reason only? Also is the oxygen attacked or the double bond attacked majorly? $\endgroup$
    – Jithin
    May 25 at 17:14
  • $\begingroup$ Remember, these processes are reversible. All possible processes happens but ultimately you got most stable product under conditions used (don't forget, 2nd step uses heating). $\endgroup$
    – Mathew Mahindaratne
    May 25 at 17:30
  • $\begingroup$ Consider the possibility that the benzene ring attacks the cation you have drawn in a 1,4 manner $\endgroup$
    – Waylander
    May 25 at 18:06
  • $\begingroup$ @Waylander this was asked in an high school exam. So I am supposed to know what majorly happens from a theoretical perspective. I mainly want to know where does the H+ attack majorly? $\endgroup$
    – Jithin
    May 26 at 7:16

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