This is a question from my textbook:

Why does the alkylation of benzene with 1-chloropropane give (propan-2-yl)benzene and not (propan-1-yl)benzene?

The book shows the reaction with chloromethane and chloroethane, and there is no such ambiguity in the two cases as the obvious products are methylbenzene and ethylbenzene respectively.

Is there a rule which I need to know in order to figure out which substituted benzene of the two would be more stable? Up till now I've only encountered Markovnikov's rule, Kharash/peroxide effect, Zaitsev's rule and Popoff's rule in the book; none of these seem to be applicable in this case.

  • $\begingroup$ Related question without answer $\endgroup$ – Jan Oct 1 '17 at 16:23
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    $\begingroup$ The gist is that 1,2-hydride shift (Wagner-Meerwein rearrangement) can create a more stable secondary carbocation from the primary pseudocation. This process is much more rapid than addition to the aromatic system. As it is half one in the morning, I’ll leave the full answer to someone else. $\endgroup$ – Jan Oct 1 '17 at 16:25
  • $\begingroup$ related chemistry.stackexchange.com/questions/38454/… $\endgroup$ – Mithoron Oct 1 '17 at 17:26

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