Esters are a class of chemical compounds and functional groups. Esters consist of an inorganic or organic acid in which at least one -OH group is replaced by an -O-alkyl group. Some acids that are commonly esterified are carboxylic acids, phosphoric acid, sulfuric acid, nitric acid, and boric acid. Volatile esters, particularly carboxylate esters, often have a pleasant smell and are found in perfumes, essential oils, and pheromones, and give...