KETENES

This article appears in Volume V15, Page 762 of the Encyclopedia Britannica.

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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

PYRIDINE

quinoline

QUINOLINE (Benzopyridine), C9H7N

, and are inert towards compounds containing the groupings C:N and C:0. The ketoketenes are coloured compounds, which undergo autoxidation readily, form ketene bases on the addition of

pyridine

PYRIDINE

and

quinoline

QUINOLINE (Benzopyridine), C9H7N

, and yield addition compounds with substances containing the C:N and C:0 groupings. The ketenes are usually obtained by the action of zinc on ethereal or

ethyl

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 platinuth 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

ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

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

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., 19o9, 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 :CO, obtained by the action of zinc on a-brom-isobutyryl bromide, is a yellowish coloured liquid. At

ordinary

ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

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). Oxygen rapidly converts it into a

white

explosive solid. Diethyl ketene, (C2H3)2C :CO, is formed on

heating

HEATING

diethylmalonic an-hydride (Staudinger, ibid.).

Diphenyl

DIPHENYL (phenyl benzene), C6H5

ketene, (C,H6)2C :CO, obtained by the action of zinc on

diphenyl

DIPHENYL (phenyl benzene), C6H5

-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.

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