1911 Encyclopædia Britannica/Benzoin (ketone-alcohol)

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BENZOIN, C6H5CHOH·CO·C6H5, a ketone-alcohol, which may be prepared by boiling an alcoholic solution of benzaldehyde with potassium cyanide; by reducing benzil (C6H5CO·CO·C6H5) with zinc and acetic acid; or by the oxidation of hydrobenzoin (C6H5-CHOH-CHOH-C6H5). It is a colourless, crystalline solid, readily soluble in alcohol and ether, melting at 137° C. and boiling at 343-344° C. On passing the vapour of benzoin over heated lead oxide, it is converted into benzil and benzophenone. Owing to the readiness with which it is oxidized, it acts as a reducing agent, giving a red precipitate of cuprous oxide with Fehling’s solution in the cold. Chlorine and nitric acid oxidize it to benzil; chromic acid mixture and potassium permanganate, to benzoic acid and benzaldehyde. On heating with zinc dust, desoxy-benzoin (C6H5CO·CH2·C6H5) is obtained; sodium amalgam converts it into hydrobenzoin; and fuming hydriodic acid at 130° C. gives dibenzyl (C6H5CH2·CH2·C6H5). By fusion with alkali it is converted into benzil; and with an alcoholic solution of benzaldehyde in presence of ammonia it forms amarine (triphenyl dihydro-glyoxaline). In the presence of sulphuric acid it condenses with nitriles to oxazoles (q.v.).