Question

Explain pinacol-pinacolone rearrangement.

Answer 1

Hint : In order to answer this question, first we will explain the given pinacol-pinacolone rearrangement, and then we will explain pinacol and pinacolone separately. And atlast we will explain why pinacol rearrangement is important in organic chemistry.

Complete Step By Step Answer:
Pinacolone rearrangement is a crucial step in the conversion of $1,2{\text{ }}diols$ into carbonyl compounds with a carbon-oxygen double bond in organic chemistry. This is accomplished through a $1,2$ - migration that occurs under acyl circumstances.
As previously mentioned, the pinacol pinacolone rearrangement occurs via a $1,2 - rearrangement$ . Two neighbouring atoms are shifted in this rearrangement. This reaction is the outcome of German chemist William Rudolph Fittig's work, which was originally documented in 1860.
Pinacol is a chemical that has two hydroxyl groups, one on each vicinal carbon atom. It's a white organic substance that's solid.
Pinacolone's IUPAC name is $3,3 -$ dimethyl - $2 -$ butanone. Pinacolone is an essential ketone. It smells like peppermint or camphor and looks to be a colourless liquid.
Pinacol-Pinacolone Rearrangement Mechanism:
Four phases are involved in the Pinacol-Pinacolone rearrangement mechanism. Each of these steps is described in detail below:
Step-1: The hydroxide group of the pinacol is protonated by the acid since the reaction is carried out in an acidic media.
Step-2: The water has been removed from the compound, leaving a carbocation behind. This carbocation is tertiary, which means it is stable.
Step-3: In a rearrangement of the molecule, the methyl group moves to the positively charged carbon.
Step-4: The oxygen atom that is doubly linked to the carbon is now deprotonated, resulting in the pinacolone that is required.

Note :
Pinacolone rearrangement is a crucial step in the conversion of $1,2{\text{ }}diols$ into carbonyl compounds with a carbon-oxygen double bond in organic chemistry. This is accomplished through a $1,2 -$ migration that occurs under acyl circumstances.