Esters are organic compounds that naturally occur in fruits, flowers, essential oils and pheromones. They are commonly used to enhance the taste and aroma of foods. Esters are also used in cosmetics, perfumes and solvents.

Esters are formed by the reaction of a carboxylic acid and an alcohol, a process that will be discussed in more detail later.

The organic family of esters contains the ester linkage ( -COO-) . This functional group resembles the carboxyl group, except that the hydrogen atom of the carboxyl group has been replaced with a hydrocarbon branch. 

Study the line structures below. They represent the esters responsible for the odour of rum and the odour of apple.