This allows us to push the reaction one way or the other by controlling concentrations, particularly of water. If we remove water from the reaction mixture, more ester is formed because carboxylic acid and alcohol react to replace the water we have removed. The resulting formation of ester is called Fischer esterification. If we add water to the reaction mixture, equilibrium is restored by the production of more carboxylic acid and alcohol. This is called acid catalyzed ester hydrolysis.
Esters can also react with amines or ammonia to form amides.
This reaction doesn't involve acid catalysis, so the first step is nucleophilic attack at the carbonyl carbon. Proton transfer follows and loss of the alcohol portion of the ester. This gives us two ways to make amides, this one from esters and the earlier one from acyl chlorides. Here's a third and very direct way to make amides, by heating carboxylic acids and amines together. Next time , we'll look at reactions of esters with Grignard reagents and with lithium aluminum hydride, and then find out how we can make synthetic use of the acidity of the hydrogen on the carbon alpha to the ester carbonyl group.