Final answer:
Transesterification requires a base to deprotonate the alcohol and facilitate the exchange of ester groups between the ester and alcohol.
Step-by-step explanation:
Transesterification is a chemical reaction that involves the exchange of ester groups between an ester and an alcohol. In this reaction, a base is typically used to deprotonate the alcohol and generate alkoxide ions. These alkoxide ions then attack the ester, leading to the formation of a new ester and an alcohol.