For this problem, we are being asked what product is obtained when the following vicinal diol is heated in an acidic solution
In this reaction, we have vicinal diol reacting with acid. This will follow a mechanism called pinacol-pinacolone rearrangement where 1,2-diols are converted to a ketone.
Pinacol-pinacolone rearrangement is subject to carbocation rearrangement since carbocations are produced in the process:
(1) protonation – the –OH group is protonated to give a better leaving group, H2O
(2) carbocation formation – the carbon-H2O bond is broken
(3) rearrangement – carbocation rearranges to form a better carbocation
(4) oxidation of OH – carbocation reforms to C=OH+
(5) deprotonation – protonated C=OH+ will be deprotonated
Step 1. Protonation of -OH:
What product is obtained when the following vicinal diol is heated in an acidic solution?