All esters; either naturally abundant or synthesized, have a common chemical structure since they are derivatives of their corresponding carboxylic acids as shown below:
Figure 1. Common Chemical Structure of Esters
Esters can be mainly prepared through esterification reaction; where carboxylic acids react with alcohols to form esters and water. Esterification reactions are catalyzed by the presence of concentrated acids to force the reaction forward preventing it from going backward. The general mechanism of the esterification reaction is displayed in the following scheme.
Figure 2. Schematic Diagram for the Mechanism of Esterification Reaction
The main role of acid in Fischer esterification reaction is acting as a catalyst since it is a dehydrating agent. It withdraws the water that is produced as a by-product of the reaction. Consequently, this forces the reaction to go forwards and prevents it from going backward.
Esters are characterized by possessing sweet odors. In addition, they are considered as the fundamental organic compounds that impart the sweet odor and taste of most fruits such as banana (isopentyl acetate), apple (methyl butyrate), and cherry (benzyl butyrate), etc.
