This article summarizes the main reactions of esters with associated practice problems. We covered the mechanism and other details about each reaction, so if you need to go over them, click on the corresponding links.
Let’s start with the hydrolysis of esters.
Esters can be hydrolyzed to carboxylic acid by acid-base catalysis. The base-catalyzed hydrolysis, also called saponification, has the advantage of being irreversible.
Esters can be converted into primary, secondary, and tertiary amides by an aminolysis reaction with ammonia, primary amine, and a secondary amine, respectively:
Esters can be reduced to alcohols or aldehydes using LiAlH4 and DIBAL, respectively:
Reacting esters with excess Grignard reagent produces tertiary alcohols:
Below is the summary of ester reactions that you can use to work on the practice problems:
To summarize, esters are carbonyl compounds and, like all carboxylic acid derivatives, their most characteristic feature is the nucleophilic addition-elimination reaction, also known as nucleophilic acyl substitution. These reactions include reduction with different reducing agents such as LiAlH4 and DIBAL-H, acid- and base-catalyzed hydrolysis, transesterification, reactions with Grignard and organolithium reagents, and the aminolysis leading to amides.
A special and very important class of esters are lactones, which are cyclic esters. Because of their ring structure, lactones often undergo interesting ring-opening reactions, and the reactivity strongly depends on the ring size and strain. Lactones are widely encountered in natural products, polymers, pharmaceuticals, and biological systems, making their chemistry especially important in organic synthesis.
In the following comprehensive set of practice problems, we will cover many important and interesting reactions of esters, including those of lactones, and apply the concepts discussed throughout this chapter to real synthetic transformations and reaction mechanisms.
