BENZOIN

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 deg. c. and boiling at 343-344 deg.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 deg. 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.).