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KETENES

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Originally appearing in Volume V15, Page 762 of the 1911 Encyclopedia Britannica.
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KETENES , in See also:

chemistry, a See also:group of organic compounds which may be considered as See also:internal anhydrides of acetic See also:acid and its substitution derivatives. Two classes may be distinguished: the aldo-ketenes, including ketene itself, together with its mono-alkyl derivatives and See also: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 See also:pyridine or See also:quinoline, and are inert towards compounds containing the groupings C:N and C:0. The ketoketenes are coloured compounds, which undergo autoxidation readily, See also:form ketene bases on the addition of pyridine and quinoline, and yield addition compounds with substances containing the C:N and C:0 groupings. The ketenes are usually obtained by the See also:action of See also:zinc on ethereal or See also:ethyl acetate solutions of halogen substituted acid chlorides or bromides. They are characterized by their additive reactions: combining with See also:water to form acids, with See also:alcohols to form See also:esters, and with See also:primary See also:amines to form amides. Ketene, See also:CH2:CO, was discovered by N. T. M. Wilsmore (Jour: Chem. See also:Soc., 1907, vol. 91, p.

1938) among the gaseous products formed when a platinuth See also:

wire is electrically heated under the See also:surface of acetic anhydride. It is also obtained by the action of zinc on bromacetyl bromide (H. Staudinger, Ber. 1908, 41, p. 594). At See also:ordinary temperatures it is a See also:gas, but it may be condensed to a liquid and finally solidified, the solid melting at -151° C. It is characterized by its penetrating See also:smell. On See also:standing for some See also:time a See also: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 See also:compound (Ber., 19o9, 42, p. 4908). It is soluble in water, the See also:solution showing an acid reaction, owing to the formation of aceto-acetic acid, and with alkalis it yields acetates.

It differs from the See also:

simple ketenes in that it is apparently unacted upon by phenols and alcohols. Dimethyl ketene, (See also:CH3)2C :CO, obtained by the action of zinc on a-brom-isobutyryl bromide, is a yellowish coloured liquid. At ordinary temperatures it rapidly polymerizes (probably to a tetramethylcylobutanedione). It boils at 34° C. (75o mm.) (Staudinger, Ber. 1905, 38, p. 1735; 1908, 41, p. 2208). See also:Oxygen rapidly converts it into a See also:white explosive solid. Diethyl ketene, (See also:C2H3)2C :CO, is formed on See also:heating diethylmalonic an-hydride (Staudinger, ibid.). See also:Diphenyl ketene, (C,H6)2C :CO, obtained by the action of zinc on diphenyl-chloracetyl chloride, is an See also:orange-red liquid which boils at 146° C. (12 mm.).

It does not polymerize. See also:

Magnesium phenyl bromide gives triphenyl vinyl See also:alcohol.

End of Article: KETENES

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