Polycarbonyl

Source: Wikipedia, the free encyclopedia.

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 zigzag of equally-spaced CO groups.[2]

Formation

Poly-CO can be produced at pressures of 5.2 GPa; it is

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

Properties

The polymer is stable above about 80 K. 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 2500 K.[6] The density is 1.65 g/cm3, 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.[4] 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.[4]

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]

Structure

Ideas of the structure include a zigzag 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 zigzags of CO.[4]

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]

References

  1. ^ a b 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. ISSN 0020-7608
    .
  3. ^ 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.
  4. ^ a b c d Bernard, Stephane (Feb 1998). "DECOMPOSITION AND POLYMERIZATION OF SOLID CARBON MONOXIDE UNDER PRESSURE" (PDF). Trieste. Retrieved 30 May 2013.
  5. ^
    ISSN 0449-1947
    .
  6. ^
    S2CID 25779399.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  7. .
  8. .
  9. .

Other reading