Methylidyne radical

Methylidyne radical
	Systematic name Hydridocarbon[1]
Identifiers
CAS number	3315-37-5
	ChEBI	CHEBI:51382 Y
Beilstein Reference	7801830
Gmelin Reference	24689
Jmol-3D images	{{#if:[CH]|Image 1
SMILES [CH]
InChI InChI=1S/CH/h1H Key: VRLIPUYDFBXWCH-UHFFFAOYSA-N
Properties
Molecular formula	CH3•
Molar mass	13.0186 g mol-1
Appearance	Colourless gas
Solubility in water	Reacts
Thermochemistry
Std enthalpy of formation ΔfHo298	594.13 kJ mol-1
Standard molar entropy So298	183.04 J K-1 mol-1
Related compounds
Related compounds	Methyl (CH3) Methylene (CH2) Carbide (C)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Methylidyne (systematically named λ¹-methane, and hydridocarbon), also called carbyne, is an organic compound with the chemical formula CH (also written as [CH]). It is a metastable gas, and classified as a very strong acid; methylidyne is corrosive.

Methylidyne is the simplest carbyne. It is a highly reactive gas, that is quickly destroyed in ordinary conditions but is abundant in the interstellar medium (and was one of the first molecules to be detected there).^[2]

Nomenclature

The trivial name carbyne is the preferred IUPAC name. The systematic names λ¹-methane, and hydridocarbon, valid IUPAC names, are constructed according to the substitutive and additive nomenclatures, respectively.

In appropriate contexts, methylidyne can be viewed as methane with three hydrogen atoms removed, and as such, methylidyne may be used as a context-specific systematic name, according to substitutive nomenclature. By default, this name pays no regard to the radicality of the methylidyne molecule. In even more specific context, the monoradical ground state is named methylylidene, whereas the triradical excited state is named methanetriyl.

Methylidyne is also used, systematically, to refer to the substituent group (≡CH). It is used, non-systematically, to refer to substituent groups methanetriyl (>CH-), and methylylidene (=CH-). Care should be taken to avoid confusing the names of the groups for the context-specific names for methylidyne given above.

Chemical properties

Methylidyne has a doublet ground state and is thus paramagnetic. It is stable in as a dilute gas, but it polymerises at high concentrations. Ground state methylidyne can be considered to be a monoradical; addition reactions are very fast and exothermic.

Acidity

The λ¹-methyl group (-C) in carbynes such as methylidyne can assimilate a hydroxy center into the molecule by ionization:

CH + OH−
→ CH
2O−

Because of this capture of the hydroxide (OH−
), methylidyne has acidic character. Its hydroxylation product is λ³-methanolate (CH
2O−
). Methylidyne does not form stable aqueous solutions, as is reduces water to elemental hydrogen.

Preparation

Methylidine can be prepared from bromoform.^[3]

Metal clusters

Methylidyne can act as a ligand in metal clusters are known. An example is HCCo
3(CO)
9.^[3]

Fischer-Tropsch intermediate

Methylidyne molecules bound to the catalyst's surface are assumed to occur as intermediates in the Fischer-Tropsch process for conversion of CO to hydrocarbons. A hypothetical sequence is

CO → COH → HC^3• → H₂C^2•

The methylene radical H₂C^2• would then insert itself into an hydrocarbon's backbone, extending it.^[4]

See also

• Methylene group
• Methylene bridge

References