KETENES, in chemistry, a class of organic compounds con taining the carbonyl group, CO, combined with either methylene, or its homologues, RCH and where R may be either an alkyl or an aryl radical (see CHEMISTRY, Organic; for other carbonyl compounds see ALDEHYDES and KETONES).
Ketene, the prototype of the series, is a colourless gas at ordinary temperature, having a penetrating odour. It has been condensed to a liquid and even solidified (melting point —151° C, boiling point —56° C). It was discovered in 1907 by N. T. M. Wilsmore among the gaseous products formed when a platinum wire is heated electrically under the surface of acetic anhydride, and was subsequently obtained by H. Staudinger (1908) by the action of zinc on bromoacetyl bromide. The latter chemist and 0. Kupfer also obtained ketene by passing carbon monoxide and diazomethane, through a quartz tube at 400-500° C.
Ketene is a remarkably active chemical substance and its production on a commercial scale would facilitate the production of many important organic chemicals (H. Dreyfus, Eng. Pat. 262,364; D. A. Nightingale, U.S.P., 1,602,699). It reacts with hydrogen chloride, ammonia and aniline, yielding respectively acetyl chloride, acetamide and acetanilide. It acetylates hydroxy
lated compounds by direct addition, the primary alcohols being most readily attacked, the tertiary alcohols and phenols least readily. When kept for some time, ketene polymerizes to a liquid dimeride boiling at 126-127° C, which combines with water to form acetoacetic acid and with aniline to yield acetoacetanilide, which is technically important as an intermediate in colour making. At 600° C, ketene decomposes into carbon monoxide and ethylene.
The homologues of ketene are divisible into two classes : (a) aldoketenes, (b) ketoketenes. The aldo-group includes ketene itself, its monoalkyl derivatives RHC:CO and carbon suboxide (see CARBON COMPOUNDS). They are colourless, do not undergo autoxidation and are polymerized by pyridine. The keto-group consists of the dialkyl and diaryl ketenes, These deriva tives are coloured, undergo autoxidation and form additive com pounds with tertiary bases, e.g., pyridine, quinoline and acridine.
See H. Staudinger, Die Ketene (Stuttgart, 1912) ; M. Sommelet, "Les Cetenes," Les Actualites de Chimie Contemporaine (Paris, 1922).
(G. T. M.)