Ketene

enUK

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.

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

单词	ketene
释义	ketene enUK ke·tene K0043300 (kē′tēn′)n. A pungent, toxic, colorless gas, C₂H₂O, used chiefly as an acetylation agent. ketene (ˈkiːtiːn; ˈkɛt-) n (Elements & Compounds) a colourless irritating toxic gas used as an acetylating agent in organic synthesis. Formula: CH2:CO. Also called: ethonone ke•tene (ˈki tin) n. a colorless poisonous gas, C₂H₂O, used chiefly in the manufacture of acetic anhydride and aspirin. [< German Keten (1905); see ketone, -ene] Ketene enUK 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. 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 ketene enUK ke·tene (kē'tēn), 1. a highly reactive acetylating agent, used in chemical syntheses. 2. Any substituted ketene.
随便看	index-organized table index out of bounds index paper index participation units index patient index plane index plate index point index pointer index portable document format index prism index prohibitorius index prohibitorum index (publishing) index rate index ratio index reference number index register index registers index rerum index (search engine) index search system index (semeiotic) index (semiotics) index sequential file description

ketene

ke·tene

ketene

ke•tene

Ketene

ketene

Ketene

REFERENCES

ketene

ke·tene