I am learning the fundamentals of organic chemistry, here is the reaction which got me stumbling me for hours, in the below reaction i could see that the amine group would get converted into diazonium salt, but i am clueless how to proceed further..


The compund A(solution) is given below, it seems like a phenyl group has migrated to the adjacent carbon, i have never seen something like this and it is also not clear for me why a carbonyl group is formed in the middle. Overall I dont understand the reaction...it would be helpful if someone points out what did i miss out in reading that made me unfit to solve this problem. Thank you!


  • $\begingroup$ It is a carbocation rearrangement, common in organic chemistry. Did you heard Pinacol Pinacolone Rearrangement? This is similar to that. $\endgroup$ Commented Jul 7, 2020 at 6:10
  • $\begingroup$ yeah i got it....but i forgot to mention in the question about the product's sterochemistry, hope u would add on it $\endgroup$
    – user91694
    Commented Jul 7, 2020 at 6:24

1 Answer 1


This is similar to pinacol-pinacolone rearrangement. Only difference is in pinacol-pinacolone rearrangement, carbocation forms by dehydration while here, it forms through diazonium reaction. Following is the tentative mechanism of the rearrangement:

pinacol-pinacolone rearrangement

Since reaction progress through carbocation intermediate, the final product is a racemic mixture. $\ce{CH3-C+-CH3}$ (in pinacol) or $\ce{CH3-C+-H}$ (in given compound) can rotate about middle horizontal bond before alkyl or aryl group migration.

  • 2
    $\begingroup$ When phenyl is the migrating group there is also the possibility of an electrophilic aromatic substitution mechanism at the ipso position (i.e. forming a cyclopropane intermediate) followed by deprotonation of the O-H bond and breaking the C-O bond. $\endgroup$
    – PCK
    Commented Jul 7, 2020 at 9:29

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