Question

Propose a mechanism for each reaction.

(a)

(b)

Short answer

(a)

(b)

Step-by-step solution

Pinacol rearrangement

Pinacol rearrangement transforms the 1, 2-diols into carbonyl compounds comprising a carbon-oxygen double bond. This happens through a 1,2-migration that happens under acyl conditions.

Products formed when the given starting material undergoes oxidation with the given reagents in reaction a

The given reactions form a category of the Pinacol-rearrangement. The first step is the protonation of a hydroxyl group. The next step is the loss of water to form a carbocation. The next step is the methyl migration forming a resonance-stabilized carbocation. The final step is the deprotonation leading to the product.

(a)The mechanism of the reaction can be given as:

Mechanism of reaction a

Products formed when the given starting material undergoes oxidation with the given reagents in reaction b

(b)The mechanism of reaction b can be given as:

Mechanism of reaction b