Tetracyanomethane

Tetracyanomethane or carbon tetracyanide is an organic compound with the chemical formula C(CN)₄. 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.^[2][3]

Tetracyanomethane

Names
Preferred IUPAC name Methanetetracarbonitrile
Other names carbon tetracyanide; 2,2-dicyanomalononitrile
Identifiers
CAS Number	24331-09-7 Y
3D model (JSmol)	Interactive image
ChemSpider	124462
PubChem CID	141101
UNII	K559RM8NV6 Y
CompTox Dashboard (EPA)	DTXSID70179070
InChI InChI=1S/C5N4/c6-1-5(2-7,3-8)4-9 Key: XKGUKYPCHPHAJL-UHFFFAOYSA-N
SMILES C(#N)C(C#N)(C#N)C#N
Properties
Chemical formula	C(CN)4
Molar mass	116.083 g·mol−1
Appearance	white crystals
Structure
Crystal structure	trigonal
Space group	R3c
Lattice constant	a = 9.062, c = 11.625
Lattice volume (V)	137.8 Å3
Formula units (Z)	6
Molecular shape	tetrahedron
Thermochemistry[1]
Std enthalpy of formation (ΔfH⦵298)	−146.2 kcal/mol
Heat of combustion, higher value (HHV)	−616.4 kcal/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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.^[2] The molecules of tetracyanomethane have a tetrahedral symmetry (43m or T_d). 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.^[3] 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.^[4] At pressures over 7 GPa tetracyanomethane starts to polymerize to form a disorganised covalent network solid. At higher pressure the white colour^[1] yellows and darkens to black. Over 20 GPa the polymerization is total.^[5]

The bulk modulus K₀ = 4.4 and its derivative K₀' = 18.^[5]

Production

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

ClCN + AgC(CN)₃ → C(CN)₄ + AgCl

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

• Cyanoform (Tricyanomethane)
• Tetraethynylmethane