ALEXANDRE-LÉON ÉTARD The Étard reaction and other contributions to chemistry

Abstract

Alexandre-Léon Étard (1852-1919) was a French chemist who studied the chemistry of chrome and its derivatives, in particular the reactions that transformed the salts of chromic oxide from one derivative into another, and the action of chlorochromic acid on organic compounds. He found that the oxidation of organic compounds followed different paths according to the nature of the substance attacked and the substitution groups present. The reaction allowed the formation of ketones or quinones, with the simultaneous release of chlorine or hydrogen chloride (the Étard reaction). This reaction transformed the methyl group attached to an aromatic nucleus into the pertinent aldehyde and allowed the synthesis of aldehydes directly from hydrocarbons. The attack of an aromatic ring yielded quinones. Étard discovered that sulfates were able to intermix to generate complex acids or neutral salts presenting coloration properties quite different from those of the simple salts from which they were derived. Together with Bémont they studied the ferricyanides and synthesized many of new complex salts; He determined the solubility of a large number of inorganic and organic salts and their mixtures as a function of the temperature, carried on the synthesis of many new organic compounds, and together with Gal determined the composition of strychnine by reacting it with a variety of chemicals.