Benzaldehyde

BENZALDEHYDE, Benzaldehyd, C₆H₆CHO (benzoyl aldehyde), a colorless or yellowish, strongly refractive liquid with a characteristic odor; dissolves in approximately 300 parts water, mixes in all proportions with alcohol and ether; boiling point 179-182°; specific gravity at 20° 1.046-1.050. Obtained by oxidation of toluene (for example, with manganese dioxide in the presence of sulfuric acid or by air when passing toluene vapor mixed with air through catalysts), as well as during the decomposition of amygdalin - a glucoside of bitter almonds, which is why benzaldehyde retained its old name - "essential oil of bitter almonds". Pure benzaldehyde introduced per os is non-toxic (Schimmel, Kohn); introduction of large doses under the skin of rabbits and frogs causes convulsions (Kobert); the toxicity of unrefined benzaldehyde obtained from amygdalin is due to the presence of HCN. It is used in medicine for preparing benzaldehyde-cyanohydrin, as well as as a corrector of taste and odor for fish oil emulsions; in addition, benzaldehyde is also used in perfumery and is an ingredient in some liqueurs and vodkas. Benzaldehyde-cyanohydrin, C₆H₅.CH(OH)CN (the nitrile of mandelic acid), the active principle of water of bitter almonds and the main constituent of essential oil of bitter almonds; obtained during the decomposition of amygdalin or synthetically by the action of HCN on benzaldehyde; a yellow, oily, water-insoluble liquid with the odor of benzaldehyde and HCN, soluble in alcohol and ether. Specific gravity 1.124, melting point -10°; decomposes at 170° into benzaldehyde and HCN. The toxic effect of benzaldehyde-cyanohydrin is due to the instability of the compound: C₆H₅.CH(OH)CN → C₆H₅CHO + HCN; according to Wirth, in the organism there are also conditions that promote the complete cleavage of the molecule. Benzaldehyde-cyanohydrin is absorbed through the skin: poisonings have been observed in humans when applied to the scalp (M. de Keitzer). Used for preparing water of bitter almonds (German Pharmacopoeia, VI).