Methylidyne Radical - Wikipedia

Methylidyne radical

Names
Preferred IUPAC name Methylidyne[1]
Systematic IUPAC name Hydridocarbonhydridocarbon(•),[2]Hydridocarbon(3•)[3]
Identifiers
CAS Number	3315-37-5
3D model (JSmol)	Interactive image
Beilstein Reference	7801830
ChEBI	CHEBI:51382 Y CHEBI:51383
Gmelin Reference	24689
CompTox Dashboard (EPA)	DTXSID701027113
InChI InChI=1S/CH/h1HKey: VRLIPUYDFBXWCH-UHFFFAOYSA-N
SMILES [CH]
Properties
Chemical formula	CH, CH•, CH3•
Molar mass	13.0186 g mol−1
Appearance	Colourless gas
Solubility in water	Reacts
Thermochemistry
Std molarentropy (S⦵298)	183.04 J K−1 mol−1
Std enthalpy offormation (ΔfH⦵298)	594.13 kJ mol−1
Related compounds
Related compounds	Methyl (CH3)Methylene (CH2)Carbide (C)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Chemical compound

Methylidyne, or (unsubstituted) carbyne, is an organic compound whose molecule consists of a single hydrogen atom bonded to a carbon atom. It is the parent compound of the carbynes, which can be seen as obtained from it by substitution of other functional groups for the hydrogen.

The carbon atom is left with either one or three unpaired electrons (unsatisfied valence bonds), depending on the molecule's excitation state; making it a radical. Accordingly, the chemical formula can be CH• or CH3• (also written as ⫶CH); each dot representing an unpaired electron. The corresponding systematic names are methylidyne or hydridocarbon(•), and methanetriyl or hydridocarbon(3•). However, the formula is often written simply as CH.

Methylidyne 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).[4]

Nomenclature

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The trivial name carbyne is the preferred IUPAC name.

Following the substitutive nomenclature, the molecule is viewed as methane with three hydrogen atoms removed, yielding the systematic name "methylidyne".

Following the additive nomenclature, the molecule is viewed as a hydrogen atom bonded to a carbon atom, yielding the name "hydridocarbon".

By default, these names pay no regard to the excitation state of the molecule. When that attribute is considered, the states with one unpaired electron are named "methylylidene" or "hydridocarbon(•)", whereas the excited states with three unpaired electrons are named "methanetriyl" or "hydridocarbon(3•)".

Bonding

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As an odd-electron species, CH is a radical. The ground state is a doublet (X2Π). The first two excited states are a quartet (with three unpaired electrons) (a4Σ−) and a doublet (A2Δ). The quartet lies at 71 kJ/mol above the ground state.[5]

Reactions of the doublet radical with non-radical species involves insertion or addition:

[CH]•(X2Π) + H2O → H• + CH2O (major) or [CH2(OH)]•

whereas reactions of the quartet radical generally involves only abstraction:

[CH]3•(a4Σ−) + H2O → [CH2] + [HO]•

Methylidyne can bind to metal atoms as tridentate ligand in coordination complexes. An example is methylidynetricobaltnonacarbonyl HCCo3(CO)9.[6]

Occurrence and reactivity

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Fischer–Tropsch intermediate

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Methylidyne-like species are implied intermediates in the Fischer–Tropsch process, the hydrogenation of CO to produce hydrocarbons. Methylidyne entities are assumed to bond to the catalyst's surface. A hypothetical sequence is:[6]

MnCO + ⁠1/2⁠ H2 → MnCOH MnCOH + H2 → MnCH + H2O MnCH + ⁠1/2⁠ H2 → MnCH2

The MnCH intermediate has a tridentate methylidine ligand. The methylene ligand (H2C) is then poised couple to CO or to another methylene, thereby growing the C–C chain.[7]

Amphotericity

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The methylylidyne group can exhibit both Lewis acidic and Lewis basic character.[8] Such behavior is only of theoretical interest since it is not possible to produce methylidyne.

In interstellar space

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In October 2016, astronomers reported that the methylidyne radical ⫶CH, the carbon-hydrogen positive ion :CH+, and the carbon ion ⫶C+ are the result of ultraviolet light from stars, rather than in other ways, such as the result of turbulent events related to supernovas and young stars, as thought earlier.[9]

Preparation

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Methylidyne can be prepared from bromoform.[6]

See also

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• Methylene group
• Methylene bridge

References

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1. ^ Henri A. Favre; Warren H. Powell (2014). Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013. Cambridge, England: Royal Society of Chemistry. p. 1054. ISBN 978-0-85404-182-4.
2. ^ "hydridocarbon (CHEBI:51382)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute. IUPAC Name.
3. ^ "hydridocarbon(3•)". Substance page at the Chemical Entities of Biological Interest (ChEBI) website, European Bioinformatics Institute, UK. Accessed on 2019-04-20
4. ^ Encyclopedia of Astrobiology, Volume 1 edited by Ricardo Amils, José Cernicharo Quintanilla, Henderson James Cleaves, William M. Irvine, Daniele Pinti, Michel Viso. 2011, Springer: Heidelberg
5. ^ Brooks, Bernard R.; Schaefer III, Henry F. (1 December 1977). "Reactions of Carbynes. Potential Energy Surfaces for the Doublet and Quartet Methylidyne (CH) Reactions with Molecular Hydrogen". The Journal of Chemical Physics. 67 (11): 5146–5151. Bibcode:1977JChPh..67.5146B. doi:10.1063/1.434743.
6. ^ a b c Nestle, Mara O.; Hallgren, John E.; Seyferth, Dietmar; Dawson, Peter; Robinson, Brian H. (1 January 1980). "μ3-Methylidyne and μ3-Benzylidyne-Tris(Tricarbonylcobalt)". In Busch, Daryle H. (ed.). Inorganic Syntheses, Vol. 20. John Wiley & Sons, Inc. pp. 226–229. doi:10.1002/9780470132517.ch53. ISBN 9780470132517.
7. ^ Herrmann, Wolfgang A. (1982). "Organometallic Aspects of the Fischer-Tropsch Synthesis". Angewandte Chemie International Edition in English. 21 (2): 117–130. doi:10.1002/anie.198201171.
8. ^ Anderson, Stuart M.; McCurdy, K. E.; Kolb, C. E. (February 1989). "The Methylidyne Radical + Carbon Monoxide Reaction: Rate Coefficient for Carbon Atom Exchange at 294 K". The Journal of Physical Chemistry. 93 (3): 1042–1048. doi:10.1021/j100340a007.
9. ^ Landau, Elizabeth (12 October 2016). "Building Blocks of Life's Building Blocks Come From Starlight". Jet Propulsion Laboratory. NASA. Retrieved 13 October 2016.

v t e Molecules detected in outer space
Molecules	Diatomic Aluminium monochloride Aluminium monofluoride Aluminium(II) oxide Argonium Carbon cation Carbon monophosphide Carbon monosulfide Carbon monoxide Cyano radical Diatomic carbon Fluoromethylidynium Helium hydride ion Hydrogen chloride Hydrogen fluoride Hydrogen (molecular) Hydroxyl radical Imidogen Iron(II) oxide Magnesium monohydride Methylidyne radical Nitric oxide Nitrogen (molecular) Oxygen (molecular) Phosphorus monoxide Phosphorus mononitride Potassium chloride Silicon carbide Silicon monoxide Silicon monosulfide Sodium chloride Sodium iodide Sulfanyl Sulfur mononitride Sulfur monoxide Titanium(II) oxide Triatomic Aluminium(I) hydroxide Aluminium isocyanide Amino radical Carbon dioxide Carbonyl sulfide CCP radical Chloronium Diazenylium Dicarbon monoxide Disilicon carbide Ethynyl radical Formyl radical Hydrogen cyanide (HCN) Hydrogen isocyanide (HNC) Hydrogen sulfide Hydroperoxyl Iron cyanide Isoformyl Magnesium cyanide Magnesium isocyanide Methylene Methylidynephosphane N2H+ Nitrous oxide Nitroxyl Ozone Potassium cyanide Sodium cyanide Sodium hydroxide Silicon carbonitride c-Silicon dicarbide SiNC Sulfur dioxide Thioformyl Thioxoethenylidene Titanium dioxide Tricarbon Trihydrogen cation Water Fouratoms Acetylene Ammonia Cyanoethynyl Formaldehyde Fulminic acid HCCN Hydrogen peroxide Hydromagnesium isocyanide Isocyanic acid Isothiocyanic acid Ketenyl Methyl cation Methyl radical Methylene amidogen Propynylidyne Protonated carbon dioxide Protonated hydrogen cyanide Silicon tricarbide Thiocyanic acid Thioformaldehyde Tricarbon monosulfide Tricarbon monoxide Fiveatoms Ammonium ion Butadiynyl Carbodiimide Cyanamide Cyanoacetylene Cyanoformaldehyde Cyanomethyl Cyclopropenylidene Formic acid Isocyanoacetylene Ketene Methane Methoxy radical Methylenimine Propadienylidene Protonated formaldehyde Silane Silicon-carbide cluster Sixatoms Acetonitrile Cyanobutadiynyl radical Cyclopropenone Diacetylene E-Cyanomethanimine Ethylene Formamide HC4N Ketenimine Methanethiol Methanol Methyl isocyanide Pentynylidyne Propynal Protonated cyanoacetylene Sevenatoms Acetaldehyde Acrylonitrile Vinyl cyanide Cyanodiacetylene Ethylene oxide Glycolonitrile Hexatriynyl radical Methyl isocyanate Methylamine Propyne Vinyl alcohol Eightatoms Acetic acid Acrolein Aminoacetonitrile Cyanoallene Ethanimine Glycolaldehyde Hexapentaenylidene Methyl formate Methylcyanoacetylene Nineatoms Acetamide Cyanohexatriyne Dimethyl ether Ethanethiol Ethanol Methyldiacetylene N-Methylformamide Octatetraynyl radical Propene Propionitrile Tenatomsor more Acetone Benzene Benzonitrile Buckminsterfullerene (C60, C60+, fullerene, buckyball) Butyronitrile C70 fullerene Cyanodecapentayne Ethyl formate Ethylene glycol Heptatrienyl radical Methyl acetate Methyl-cyano-diacetylene Methyltriacetylene Propionaldehyde Pyrimidine
Deuteratedmolecules	Ammonia Ammonium ion Formaldehyde Formyl radical Heavy water Hydrogen cyanide Hydrogen deuteride Hydrogen isocyanide N2D+ Propyne Trihydrogen cation
Unconfirmed	Anthracene Dihydroxyacetone Glycine Graphene H2NCO+ Hemolithin Linear C5 Methoxyethane Naphthalene cation Phosphine Pyrene Silylidyne
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