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Polycarbonyl, (also known as polymeric-CO, p-CO or poly-CO) is a solid metastable and explosive polymer of carbon monoxide.[1] The polymer is produced by exposing carbon monoxide to high pressures. The structure of the solid appears amorphous, but may include a zig zag of equally spaced CO groups.[2]


Poly-CO can be produced at pressures of 5.2 GPa. Polymerisation is catalysed by blue light at slightly lower pressures in the δ-phase of solid CO.[3] Another white phase can be made at higher temperatures at 6 or 7 GPa.[1] Poly-CO appears to be a yellow to dark red amorphous phase.[4] Whereas the white phase appears to be crystalline.[1]

R. J. Mills discovered this solid, which was first produced in a tungsten carbide anvil in 1947. Originally this was thought to be polymeric carbon suboxide, but the formation does not yield any gas byproduct such as carbon dioxide.[5] The yield of the solid can be up to 95%.[6]


The polymer is stable above about 80K. Below this temperature the ε form of solid molecular CO is formed instead. When the pressure is released the polymer remains stable at atmospheric pressure. The solid dissolves in water, alcohol and acetone.[5] When exposed to the atmosphere it is hygroscopic, becomes gluey, and changes colour, becoming darker.[6] The reaction with water produces carboxylic groups.[7][8]

The solid stores a high energy. It can decompose explosively forming glassy carbon and carbon dioxide.[6] The energy density stored can be up to 8 kJ/g. During the decomposition the temperature can be 2500K.[6] The density is 1.65 gcm−3, however most of the solid produced is porous, so the true density is likely to be higher.[6]

Infrared spectroscopy shows bands at 650, 1210, 1440, 1650 and 1760 cm−1. The 1760 band is likely to be due to the -C-(C=O)-C- structure.[3] The 1600 is due to vibration of a C=C double bond.[6]

The solid is electrically insulating with an electronic gap energy of 1.9 eV.[3]

Nuclear magnetic resonance for the material made from 13CO shows sharp resonance at 223 ppm due to ester or lactone attached carbon, and 151 ppm due to C=C double bonds. There is also broad resonance at 109 and 189 ppm. Over time of a few days, the 223 ppm peak reduces and all the other features increase in strength.[6]


Ideas of the structure include a zig zag chain of CO pointing in opposite directions, or five atom rings connected by CO and C-C bonds. The rings are lactones of tetronic acid: -C:-(C=O)-(C-O-)-(C=O)-O-. Interconnections between the rings are zig zags of CO.[3]

Other ideas of the structure of the solid, include graphitic carbon with carbon dioxide under pressure, and a polymer with this C3O2 monomer: -(C=O)-O-(C-)=C<. Yet other ideas are that the solid is the same as the polymer of carbon suboxide with oxalic anhydride.[9]


  1. 1.0 1.1 1.2 Rademacher, N.; L. Bayarjargal; W. Morgenroth; B. Winkler; J. Ciezak-Jenkins (2011). "Preparation and characterization of solid carbon monoxide at high pressure in the diamond anvil cell" (PDF). Retrieved 30 May 2013. 
  2. Podeszwa, Rafał; Rodney J. Bartlett (2003). "Crystal orbital study of polycarbonyl". International Journal of Quantum Chemistry. 95 (4–5): 638–642. ISSN 0020-7608. doi:10.1002/qua.10655. 
  3. 3.0 3.1 3.2 3.3 Bernard, Stephane (Feb 1998). "DECOMPOSITION AND POLYMERIZATION OF SOLID CARBON MONOXIDE UNDER PRESSURE" (PDF). Trieste. Retrieved 30 May 2013. 
  4. Rademacher, Nadine; Lkhamsuren Bayarjargal; Wolfgang Morgenroth; Jennifer Ciezak-Jenkins; Sasha Batyrev; Björn Winkler. "High Pressure Investigations of Liquid and Polymerized CO up to 20 GPa Using Pair Distribution Function Analysis" (PDF). Retrieved 30 May 2013. 
  5. 5.0 5.1 Mills, R. L.; D. Schiferl; A. I. Katz; B. W. Olinger (1984). "NEW PHASES AND CHEMICAL REACTIONS IN SOLID CO UNDER PRESSURE" (PDF). Le Journal de Physique Colloques. 45 (C8): C8–187–C8–190. ISSN 0449-1947. doi:10.1051/jphyscol:1984833. 
  6. 6.0 6.1 6.2 6.3 6.4 6.5 6.6 Lipp, Magnus J.; William J. Evans, Bruce J. Baer, Choong-Shik Yoo; Baer, Bruce J.; Yoo, Choong-Shik (2005). "High-energy-density extended CO solid" (PDF). Nature Materials. 4 (3): 211–215. Bibcode:2005NatMa...4..211L. ISSN 1476-1122. PMID 15711555. doi:10.1038/nmat1321. 
  7. Ceppatelli, Matteo; Anton Serdyukov; Roberto Bini; Hans J. Jodl (2009). "Pressure Induced Reactivity of Solid CO by FTIR Studies". The Journal of Physical Chemistry B. 113 (19): 6652–6660. ISSN 1520-6106. PMID 19368397. doi:10.1021/jp900586a. 
  8. Katz, Allen I.; David Schiferl; Robert L. Mills (1984). "New phases and chemical reactions in solid carbon monoxide under pressure". The Journal of Physical Chemistry. 88 (15): 3176–3179. ISSN 0022-3654. doi:10.1021/j150659a007. 
  9. Lipp, M.; W. J. Evans; V. Garcia-Baonza; H. E. Lorenzana (1998). "Carbon Monoxide: Spectroscopic Characterization of the High–Pressure Polymerized Phase". Journal of Low Temperature Physics. 111 (3/4): 247–256. Bibcode:1998JLTP..111..247L. ISSN 0022-2291. doi:10.1023/A:1022267115640. 

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