KETENES

ketenes, in chemistry, a group of organic compounds which may be considered as internal anhydrides of acetic acid and its substitution derivatives. two classes may be distinguished: the aldo-ketenes, including ketene itself, together with its mono-alkyl derivatives and carbon suboxide, and the keto-ketenes which comprise the dialkyl ketenes. the aldo-ketenes are colourless compounds which are not capable of autoxidation, are polymerized by pyridine or quinoline, and are inert towards compounds containing the groupings c:n and c:o. the keto-ketenes are coloured compounds, which undergo autoxidation readily, form ketene bases on the addition of pyridine and quinoline, and yield addition compounds with substances containing the c:n and c:o groupings. the ketenes are usually obtained by the action of zinc on ethereal or ethyl acetate solutions of halogen substituted acid chlorides or bromides. they are characterized by their additive reactions: combining with water to form acids, with alcohols to form esters, and with primary amines to form amides. _ketene_, ch2:co, was discovered by n. t. m. wilsmore (_jour. chem. soc._, 1907, vol. 91, p. 1938) among the gaseous products formed when a platinum wire is electrically heated under the surface of acetic anhydride. it is also obtained by the action of zinc on bromacetyl bromide (h. staudinger, _ber._ 1908, 41, p. 594). at ordinary temperatures it is a gas, but it may be condensed to a liquid and finally solidified, the solid melting at -151° c. it is characterized by its penetrating smell. on standing for some time a brown-coloured liquid is obtained, from which a colourless liquid boiling at 126-127° c., has been isolated (wilsmore, ibid., 1908, 93, p. 946). although originally described as acetylketen, it has proved to be a cyclic compound (ber., 1909, 42, p. 4908). it is soluble in water, the solution showing an acid reaction, owing to the formation of aceto-acetic acid, and with alkalis it yields acetates. it differs from the simple ketenes in that it is apparently unacted upon by phenols and alcohols. _dimethyl ketene_, (ch3)2c:co1 obtained by the action of zinc on [alpha]-brom-isobutyryl bromide, is a yellowish coloured liquid. at ordinary temperatures it rapidly polymerizes (probably to a tetramethylcylobutanedione). it boils at 34° c (750 mm.) (staudinger, ber. 1905, 38, p. 1735; 1908, 41, p. 2208). oxygen rapidly converts it into a white explosive solid. _diethyl ketene_, (c2h5)2c:co, is formed on heating diethylmalonic anhydride (staudinger, ibid.). _diphenyl ketene_, (c6h5)2c:co, obtained by the action of zinc on diphenyl-chloracetyl chloride, is an orange-red liquid which boils at 146° c. (12 mm.). it does not polymerize. magnesium phenyl bromide gives triphenyl vinyl alcohol.