The question in my worksheet asks me to predict the result of the reaction between benezene and $\ce{(CH3CH2CH2CO)2O}$ in presence of anhydrous $\ce{AlCl3}$.

My attempt:

After complex formation with $\ce{AlCl3}$ we get this carbocation: $\ce{CH3CH2CH2CO+}$ that has two resonance structures.

But, if we consider hydride shift we get $\ce{CH3CH2C^+HC=O}$ which is not only stabilised by resonance but also by the $\text{+I}$ effect of ethyl group.

However, the answer is $\ce{PhCOCH2CH2CH3}$ which isn't formed by the second carbocation with hydride shift .

So I'd like to know if hydride shift is possible in ketonic carbocations or not? And if it is, is the answer wrong?

  • 2
    $\begingroup$ If hydride transfer were to occur, the resultant carbonyl would be stabilizing a cation. A definite NO_NO! Read up on the the Friedel-Crafts reaction. $\endgroup$
    – user55119
    Mar 21, 2018 at 16:09

1 Answer 1


The carbocation doesn't rearrange since oxygen donates it's lone pair and the resulting carbocation is quite stable since the octet of all the atoms is complete. enter image description here


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.