Question

Draw a stepwise mechanism for the following reaction

Short answer

Acid-catalyzed nucleophilic addition involves conversion of the neutral carbonyl group to a positively charged system. The positively charged oxygen makes the carbon attached to it, more electrophilic and hence prone to nucleophilic attack.

The general mechanism is given below:

Acid-catalyzed nucleophilic addition

Step-by-step solution

Acid-catalyzed nucleophilic addition of aldehydes or ketones

Acid-catalyzed nucleophilic addition involves conversion of the neutral carbonyl group to a positively charged system. The positively charged oxygen makes the carbon attached to it, more electrophilic and hence prone to nucleophilic attack.

The general mechanism is given below:

Acid-catalyzed nucleophilic addition

Mechanism of the given reaction

The given reaction is:

Reaction given

The reaction starts with the protonation of the highly reaction ketone group. As the carbon center of the carbonyl group becomes more electrophilic, the acetal group acts as a nucleophile and attacks at the electrophilic center.

Protonation of oxygen making the carbonyl carbon center more electrophilic

The reaction further proceeds as shown below:

Mechanism of the reaction

Upon further nucleophilic attack at the C=OMe center, the product is obtained, as shown below:

Further nucleophilic attack and formation of product