Methenium

In organic chemistry, methenium (also called methylium, carbenium,[2] methyl cation, or protonated methylene) is a cation with the formula CH+
3. It can be viewed as a methylene radical (:CH
2) with an added proton (H+
), or as a methyl radical (•CH
3) with one electron removed. It is a carbocation and an enium ion, making it the simplest of the carbenium ions.[3]

Not to be confused with methanium.
Methenium
Names
Preferred IUPAC name
Methylium[1]
Other names
Methyl cation; Carbanylium
Identifiers
3D model (JSmol)
1839325
ChEBI
ChemSpider
48893
UNII
  • InChI=1S/CH3/h1H3/q+1
    Key: JUHDUIDUEUEQND-UHFFFAOYSA-N
  • [CH3+]
Properties
CH3+
Molar mass 15.034 g·mol−1
Related compounds
borane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Structure

Experiments and calculations generally agree that the methenium ion is planar, with threefold symmetry.[3] The carbon atom is a prototypical (and exact) example of sp2 hybridization.

Preparation and reactions

For mass spectrometry studies at low pressure, methenium can be obtained by ultraviolet photoionization of methyl radical,[3] or by collisions of monatomic cations such as C+
 and Kr+
 with neutral methane.[4] In such conditions, it will react with acetonitrile CH
3CN to form the ion (CH
3)
2CN+
.[5]

Upon capture of a low-energy electron (less than 1 eV), it will spontaneously dissociate.[6]

It is seldom encountered as an intermediate in the condensed phase. It is proposed as a reactive intermediate that forms upon protonation or hydride abstraction of methane with FSO3H-SbF5. The methenium ion is very reactive, even towards alkanes.[7]

Detection
Main article: List of interstellar and circumstellar molecules

Origins of life

In June 2023, astronomers detected, for the first time outside the Solar System, methyl cation, CH3+ (and/or carbon cation, C+), the known basic ingredients of life, in interstellar space.[8][9]

See also

References
  1. International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 1089. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
  2. "Ions, Free Radicals, and Radical-Ion", Nomenclature of Organic Compounds, Advances in Chemistry, vol. 126, AMERICAN CHEMICAL SOCIETY, June 1974, pp. 216–224, doi:10.1021/ba-1974-0126.ch028, ISBN 978-0841201910
  3. Golob, L.; Jonathan, N.; Morris, A.; Okuda, M.; Ross, K.J. (1972). "The first ionization potential of the methyl radical as determined by photoelectron spectroscopy". Journal of Electron Spectroscopy and Related Phenomena. 1 (5). Elsevier BV: 506–508. doi:10.1016/0368-2048(72)80022-7. ISSN 0368-2048.
  4. Sharma, R. B.; Semo, N. M.; Koski, W. S. (1987). "Dynamics of the reactions of methylium, methylene radical cation, and methyliumylidene with acetylene". The Journal of Physical Chemistry. 91 (15). American Chemical Society (ACS): 4127–4131. doi:10.1021/j100299a037. ISSN 0022-3654.
  5. McEwan, Murray J.; Denison, Arthur B.; Huntress, Wesley T.; Anicich, Vincent G.; Snodgrass, J.; Bowers, M. T. (1989). "Association reactions at low pressure. 2. The methylium/methyl cyanide system". The Journal of Physical Chemistry. 93 (10). American Chemical Society (ACS): 4064–4068. doi:10.1021/j100347a039. ISSN 0022-3654.
  6. Bahati, E. M.; Fogle, M.; Vane, C. R.; Bannister, M. E.; Thomas, R. D.; Zhaunerchyk, V. (2009-05-11). "Electron-impact dissociation of CD+
    3     and CH+
    3     ions producing CD+
    2    , CH+
     and C+
     fragment ions". Physical Review A. 79 (5). American Physical Society (APS): 052703. doi:10.1103/physreva.79.052703. ISSN 1050-2947.
  7. Hogeveen, H.; Lukas, J.; Roobeek, C. F. (1969). "Trapping of the methyl cation by carbon monoxide; formation of acetic acid from methane". Journal of the Chemical Society D: Chemical Communications (16): 920. doi:10.1039/c29690000920. ISSN 0577-6171.
  8. Sauers, Elisha (27 June 2023). "Webb telescope just found something unprecedented in the Orion Nebula - Astronomers are excited about the detection of a special molecule in space". Mashable. Archived from the original on 27 June 2023. Retrieved 27 June 2023.
  9. Berné, Olivier; et al. (26 June 2023). "Formation of the Methyl Cation by Photochemistry in a Protoplanetary Disk". Nature. 621 (7977): 56–59. arXiv:2401.03296. doi:10.1038/s41586-023-06307-x. hdl:1887/3716674. PMID 37364766. S2CID 259260435. Archived from the original on 27 June 2023. Retrieved 27 June 2023.
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