Esters
ethereal salts formed by the reaction between an acid and an alcohol.
For instance C2H5OH + HCI Alcohol Hydrochloric Acid C2H5Cl + H₂O Ethyl Chloride Water Ethyl Chloride is the hydrochloric acid ester of ethyl alcohol. The change from an alcohol to an ester is never complete, because the reaction is reversible; that is to say, esters are decomposed by water, giving acid and alcohol. When an alcohol and an acid are mixed, therefore, the reaction illustrated above proceeds to a certain point until a balance, or equilibrium, is reached, the final product being a mixture of alcohol, acid, ester, and water. If, however, the water produced is removed, and so prevented from decomposing the ester, the reaction is far more nearly complete, and it is a common practice to employ, a dehydrating agent, such as sulphuric acid, which combines with the water as fast as it is formed.
Esters are usually pleasant-smelling, colorless liquids, and the odor of flowers and fruits is frequently due to their presence. Many artificial flavorings, essences, and perfumes consist of esters. Some of the best known are methyl salicylate (oil of wintergreen) amyl acetate (banana or pear oil) methyl butyrate (pineapple oil) and isoamyl isovalerate (apple oil).
ESTHER (es'ter), a Jewess who became the queen of Ahasuerus, King of Persia, and whose story is told in the book of the Old Testament called by her name. This book is supposed by some to be the composition of Mordecai himself, the uncle of the heroine. The feast of Purim, which commemorates the events narrated, is still observed by the Jews during the month Adar.