Ester

An ester is a product of a carboxylic acid and an alcohol joined together by an ester bond. This reaction is known as esterification, where an alcohol and carboxylate acid join in the presence of an acid catalyst forming an ester and the by product is water. Typically, concentrated sulphuric acid is used as the catalyst in esterification in this reaction sulphuric acid is a good example of a homogenous catalyst as it is in the same phase as the reactants (liquid phase). Esters are used in foods and in purfumes and can be also formed from acid anhydrides and broken down by acid and alkaline hydrolysis back into the original carboxylic acid and alcohol.