Synthesis of banana oil

Many esters can be synthesized simply by mixing together a carboxylic acid and an alcohol, along with a catalytic amount of sulfuric acid.  A popular reaction in undergraduate organic lab courses is the preparation of isopentyl acetate (also called ‘banana oil’ because it is a flavor component in bananas) from acetic acid and isopentyl alcohol.

Notice the double arrows in the above figure: because esters and carboxylic acids are of approximately the same stability, this esterification reaction is highly reversible.

The main role of the acid catalyst in this reaction is to protonate the carboxylic acid, thus making the carbonyl carbon more electrophilic.

Many other fragrant esters can be synthesized in similar reactions.  A few examples of esters found in foods are given below.