Question

Propose a mechanism for the acid-catalyzed hydrolysis of cyclohexanone dimethyl acetal.

Short answer

Dilute aqueous acid can be used for the hydrolysis of cyclohexanone dimethyl acetal. The mechanism is shown below.

Step-by-step solution

Acetals

The compound in whichtwo alkoxy groups are attached with the same carbon atom is termed as acetal. Aldehyde and ketones react with alcohols to form hemiacetal and acetal. The reaction occurs in the presence of acids.

Mechanism of the reaction

The acid-catalyzed hydrolysis of cyclohexanone dimethyl acetal occurs in five steps. In the first step, the protonation of acetal occurs. In the second step, the lone pair present on the second oxygen atom shifts beween the carbon and oxygen and removal of methanol occurs. In the third step, water molecules attack the carbonyl carbon and pi-bond electrons move to the oxygen atom.

In the fourth step, the transfer of proton and the removal of methanol molecule occurs. In the last step, the deprotonation takes place and cyclohexanone is obtained as the major product.