Tetracyanomethane or carbon tetracyanide is a
percyanoalkane molecular
carbon nitride
In organic chemistry, carbon nitrides are compounds consisting only of carbon and nitrogen atoms.
Covalent network compounds
* Beta carbon nitride - a solid with a formula β-, which is predicted to be harder than diamond.
* Graphitic carbon ...
with formula C(CN)
4. The structure can be considered as
methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...
with all hydrogen atoms replaced by
cyanide
Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms.
In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...
groups. It was first made by
Erwin Mayer in 1969.
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.
[
The molecules of tetracyanomethane have a ]tetrahedral
In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all the o ...
symmetry (3''m'' 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.[ 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
Carbon tetrachloride, also known by many other names (such as tetrachloromethane, also IUPAC nomenclature of inorganic chemistry, recognised by the IUPAC, carbon tet in the cleaning industry, Halon-104 in firefighting, and Refrigerant-10 in HVAC ...
, 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 colour yellows and darkens to black. Over 20 GPa the polymerization is total.][
]
Production
Tetracyanomethane can be made by reacting cyanogen chloride
Cyanogen chloride is a highly toxic chemical compound with the formula CNCl. This linear, triatomic pseudohalogen is an easily condensed colorless gas. More commonly encountered in the laboratory is the related compound cyanogen bromide, a room-tem ...
with silver tricyanomethanide.
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
Cyanate is an anion with the structural formula , usually written . It also refers to any salt containing it, such as ammonium cyanate.
It is an isomer of the much less stable fulminate anion .William R. Martin and David W. Ball (2019): "Small ...
ions are produced.[
]
See also
* Tricyanomethane (cyanoform)
References
{{Cyanides, state=collapsed
Nitriles