Chemical elements
  Carbon
    Isotopes
    Energy
    Production
    Application
    Physical Properties
    Chemical Properties
      Methane
      Ethylene
      Acetylene
      Coal-Gas
      Carbon Tetrafluoride
      Tetrafluoromethane
      Carbon Tetrachloride
      Tetrachloromethane
      Carbon Tetrabromide
      Tetrabromomethane
      Carbon Tetraiodide
      Tetraiodomethane
      Carbon Oxychloride
      Carbonyl Chloride
      Phosgene
      Carbon Oxybromide
      Carbonyl Bromide
      Carbon Suboxide
      Carbon Monoxide
      Carbon Dioxide
      Percarbonic Acid
      Carbamic Acid
      Carbamide
      Urea
      Carbon Disulphide
      Carbonyl Sulphide
      Carbon Oxysulphide
      Thiocarbonyl Chloride
      Thiocarbonic Acid
      Thiocarbamic acid
      Thiourea
      Thiocarbamide
      Perthiocarbonates
      Carbon Monosulphide
      Carbon Subsulphide
      Carbon Sulphidoselenide
      Carbon Sulphidotelluride
      Carbon Nitrides
      Cyanogen
      Dicyanogen
      Hydrocyanic Acid
      Prussic Acid
      Cyanogen Chloride
      Chlorocyanogen
      Cyanogen Bromide
      Bromocyanogen
      Cyanogen Iodide
      Iodocyanogen
      Polymerised Cyanogen Halides
      Cyanamide
      Cyanic Acid
      Cyanuric Acid
      Cyamelide
      Fulminic Acid
      Thiocyanic Acid
      Sulphocyanic Acid
      Isoperthiocyanic Acid
      Cyanogen Sulphide
      Thiocyanic Anhydride
    Diamonds
    Graphite
    Amorphous Carbon
    Coal

Carbon Suboxide, C3O2






Carbon Suboxide, C3O2, is among the products of the distillation of ethyl malonate at 300° C. and a pressure of 12 mm. over a large excess of phosphoric oxide. Other malonic esters and the esters of related acids, as well as malonic acid itself, can similarly be made to yield the suboxide by a reaction which is essentially

CH2(COOH)2 = C3O2 + 2H2O.

The suboxide is freed from ethylene and carbon dioxide, formed at the same time, by allowing the distillate, condensed by liquid air, to boil at atmospheric temperature; the residue is then vaporised, and collected at -60° C. Carbon suboxide is also formed by the interaction of malonyl chloride with silver, lead, or zinc oxide, thus:

CH2(COCl)2 + Ag2O = C3O2 + 2AgCl + H2O.

Silver oxalate or malonate may be employed in place of the oxide. Carbon suboxide is a colourless, mobile, refractive liquid having an odour which resembles that of acraldehyde and mustard oil, and is poisonous. It boils at 7° C. under 761 mm. pressure, and its vapour density corresponds to the formula C3O2. It burns with a bright blue smoky flame, producing carbon dioxide according to the reaction: C3O2 + 2O2 = 3CO2. The liquid oxide slowly changes at atmospheric temperature into a dark red solid of approximately the same composition, whose aqueous solution is eosin-red. This change, which is partly one of decomposition, is rapid at 37° C. and instantaneous at 100° C. The oxide combines with water to form malonic acid, and with hydrogen chloride, ammonia, and aniline to form malonyl chloride, malonamide, and malonanilide respectively. Its discoverers therefore regarded it as the second anhydride of malonic acid, thus:



Michael considers the oxide to be the lactone of β-hydroxy-propriolic acid, and thus to have the constitution ; but this view is not acceptable to Diels and Meyerheim, who adhere to the "dioxoallene" formula, O:C:C:C:O; and Diels and Lalin have shown that the suboxide behaves as a ketene, giving with formic acid the additive compound: .

Berthelot claimed that the term "carbon suboxide" is properly applied to the compounds discovered previously by Brodie and himself, and therefore cannot legitimately be used for the compound C3O2.


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