what is an ester

An ester is a chemical compound derived from an acid (organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group (−OH) of that acid is replaced by an organyl group/Esters/Properties_of_Esters). Esters are usually derived from carboxylic acids, which contain the -COOH group, and in an ester, the hydrogen in this group is replaced by a hydrocarbon group of some kind/Esters/Properties_of_Esters). Esters can be formed by a chemical reaction called esterification, which involves two reactants (typically an alcohol and an acid) forming an ester as the reaction product/Esters/Properties_of_Esters). Esters are common in organic chemistry and biological materials and often have a pleasant characteristic, fruity odor, which leads to their extensive use in the fragrance and flavor industry. Esters are also widespread in nature and are responsible for the aroma of many fruits, including apples, durians, pears, bananas, pineapples, and strawberries. Several billion kilograms of polyesters are produced industrially annually, important products being polyethylene terephthalate, acrylate esters, and cellulose acetate.