Tetracyanomethane Explained

Tetracyanomethane or carbon tetracyanide is an organic compound with the chemical formula . It is a percyanoalkane. It is a molecular carbon nitride. The structure can be considered as methane with all hydrogen atoms replaced by cyanide groups. It was first made by Erwin Mayer in 1969.[1] [2]

Properties

Tetracyanomethane is a solid at room temperature. It decomposes over 160 °C without melting, and although it can be in a dilute vapour, no liquid form is known.[1] The molecules of tetracyanomethane have a tetrahedral symmetry (3m or Td). The molecule has C-C distance of 1.484 Å and C-N distance of 1.161 Å in the gas form. In the solid the C≡N bond shortens to 1.147 Å.[2] The C-C bond has a force constant of 4.86×105 dyn/cm which is slightly greater than the C-Cl bond in carbon tetrachloride, but a fair bit weaker than in the tricyanomethanide ion. At pressures over 7 GPa tetracyanomethane starts to polymerize to form a disorganised covalent network solid. At higher pressure the white colour yellows and darkens to black. Over 20 GPa the polymerization is total.[3]

The bulk modulus K0 = 4.4 and its derivative K0' = 18.[3]

Production

Tetracyanomethane can be made by reacting cyanogen chloride with silver tricyanomethanide.[4]

Reactions

In an acid solution in water tetracyanomethane is hydrolysed to yield tricyanomethanide and ammonium ions along with carbon dioxide. In alkaline solutions tricyanomethanide and cyanate ions are produced.[4]

See also

Notes and References

  1. Mayer . Erwin . Darstellung und Eigenschaften von Tetracyanmethan . Monatshefte für Chemie . 1969 . 100 . 2 . 462–468 . 10.1007/BF00904089. 92450428 .
  2. Britton . D. . The crystal structure of tetracyanomethane, C(CN)4 . Acta Crystallographica Section B. 1 July 1974 . 30 . 7 . 1818–1821 . 10.1107/S0567740874005863. 1974AcCrB..30.1818B .
  3. Keefer . Derek W. . Gou . Huiyang . Wang . Qianqian . Purdy . Andrew . Epshteyn . Albert . Juhl . Stephen J. . Cody . George D. . Badding . John . Strobel . Timothy A. . Tetracyanomethane under Pressure: Extended CN Polymers from Precursors with Built-in sp3 Centers . The Journal of Physical Chemistry A . 12 February 2018 . 122 . 11 . 2858–2863 . 10.1021/acs.jpca.7b10729. 29432685 . 2018JPCA..122.2858K . 1430339 .
  4. Hester . Ronald E. . Lee . Kenneth Michael . Mayer . Erwin . Tetracyanomethane as a pseudo-(carbon tetrahalide) . The Journal of Physical Chemistry . September 1970 . 74 . 18 . 3373–3376 . 10.1021/j100712a011.