Ketene


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ketene

[′kē‚tēn]
(organic chemistry)
C2H2O A colorless, toxic, highly reactive gas, with disagreeable taste; boils at -56°C; soluble in ether and acetone, and decomposes in water and alcohol; used as an acetylating agent in organic synthesis.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Ketene

 

carbomethene, the first member of the ketene series (RR’C=C=0), the unsaturated, highly reactive organic compound CH2=C=0.

Ketene is a gas (boiling point, 41°C; melting point, 134.6°C) and serves as an effective acetylizing agent; acetylation products form upon the reaction of ketene with compounds containing a mobile hydrogen atom (for example, alcohols, thiols, amines, and acids):

ROH + CH2=C= O → ROCOCH3

Ketene combines readily with water to form acetic acid and ketones. For example, dimethyl-β-propiolactone is obtained from ketene and acetone:

Ketene is stable at –80°C. At 0°C it readily undergoes dimerization to form diketene (methylene-β-propiolactone)

from which ketene can be regenerated by pyrolysis at 550°-600°C. Ketene is similar to phosgene in terms of toxicity.

The industrial preparation of ketene involves the pyrolysis of acetic acid in the presence of triethyl phosphate or the pyrolysis of acetone over alumina. The common method of synthesizing ketene and other compounds of the ketene series consists in the separation of halogens from the acid halides of α-halocarboxylic acids:

RR’CX—COX→ RR’C = C = 0 + ZnX2

(X being a halogen atom)

Ketene is easily obtained in the laboratory by the pyrolysis of acetone or acetic anhydride in a special apparatus called a ketene lamp.

Ketene is used in industry for converting acetic acid to anhydride, preparing acetylcellulose, and synthesizing propiolactone.

REFERENCES

Lacey, R. N. “Keten ν organicheskom sinteze.” In the book Uspekhi organicheskoi khimii, vol. 2. Moscow, 1964. Page 204. (Translated from English.)

IA. F. KOMISSAROV

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Internal Sizing II: Alkaline Ketene Dimer Sizes (AKD).
Tomita, "Enantioselective addition of ketene silyl acetals to nitrones catalyzed by chiral titanium complexes.
Cengiz Ketene, Erdoy-an's Arabic interpreter, told Sunday's Zaman that the ceiling of a simultaneous interpretation cabin he was in collapsed during a conference.
These were of interest because Woodward and Hoffmann suggested that the reaction could be viewed as a concerted (2[[pi].sub.s] + 2[[pi].sub.a]) cycloaddition with a transition state characterized by crossed, mutually perpendicular molecular planes of ketene and the alkene.
Natural silk of Margelan masters, famous Rishtan ceramics from Uzbekistan and interesting ceramic items produced by Kyrgyz potters from Bishkek and Osh, diverse felt items from various oblasts of Kyrgyzstan, silver jewelries from Kazakhstan, ketene natural fabrics from Turkmenistan, traditional embroideries from Tajikistan and many other handicraft products are very popular among visitors, organizers say.
Internal sizing is usually done by wet-end fiber modifications, using either nonreactive agents (e.g., rosin) or synthetic agents that chemically react with the cellulose hydroxyl groups to form stable ester linkages (e.g., alkene ketene dimers, alkenyl succinic anhydride).
Polyorthoester (POE) can be created by reacting ketene acetals with diols.
Jose MARTINEZ GAZQUEZ, Observaciones a la traduccion latina del Coran (Qur'an) de Robert de Ketene, in Jacqueline HAMESSE (ed.), Les traducteurs au travail.
The centre manufactured 15kg of a special kind of paper from cotton and ketene to fill the gaps in the pages.
As an example we studied the deposition of micron-sized Alkyl Ketene Dimer (AKD) particles on pulp fibres by cationic polyacrylamide (cPAM), a common flocculent.