Methenium: Difference between revisions
Alsosaid1987 (talk | contribs) it is also called the parent carbenium ion. experimental observation and all levels of theory find that methyl cation is exactly planar, so removed the phrase "nearly planar" |
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[[File:Methyl_cation.svg|thumb|180px|right|Methenium ({{chem|CH|3|+}}).]] |
[[File:Methyl_cation.svg|thumb|180px|right|Methenium ({{chem|CH|3|+}}).]] |
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In [[organic chemistry]], '''methenium''' (also called '''methylium''', '''carbenium''',<ref>{{Citation|title=Ions, Free Radicals, and Radical-Ion|date=1974 |
In [[organic chemistry]], '''methenium''' (also called '''methylium''', '''carbenium''',<ref>{{Citation|title=Ions, Free Radicals, and Radical-Ion|date=June 1974|url=https://pubs.acs.org/doi/abs/10.1021/ba-1974-0126.ch028|work=Advances in Chemistry|pages=216–224|publisher=AMERICAN CHEMICAL SOCIETY|language=EN|doi=10.1021/ba-1974-0126.ch028|isbn=0841201919|access-date=2018-11-03}}</ref> '''methyl cation''', or '''protonated methylene''') is a [[cation|positive ion]] with the formula {{chem|CH|3|+}}. It can be viewed as a [[methylene radical]] (''':'''{{chem|CH|2}}) with an added [[proton]] ({{chem|H|+}}), or as a [[methyl radical]] (•{{chem|CH|3}}) with one [[electron]] removed. It is a [[carbocation]] and an [[enium compound|enium ion]], making it the simplest of the [[carbenium ion]]s.<ref name=Golob/> |
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== Structure == |
== Structure == |
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Revision as of 21:19, 12 November 2018
3).
In organic chemistry, methenium (also called methylium, carbenium,[1] methyl cation, or protonated methylene) is a positive ion 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.[2]
Structure
Experiments and calculations generally agree that the methenium ion is planar, with threefold symmetry.[2] 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,[2] or by collisions of monatomic cations like C+
and Kr+
with neutral methane.[3] In such conditions, it will react with acetonitrile CH
3CN to form the ion (CH
3)
2CN+
.[4]
Upon capture of a low-energy electron (less than 1 eV), it will spontaneously dissociate.[5]
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.[6]
References
- ^ "Ions, Free Radicals, and Radical-Ion", Advances in Chemistry, AMERICAN CHEMICAL SOCIETY, pp. 216–224, June 1974, doi:10.1021/ba-1974-0126.ch028, ISBN 0841201919, retrieved 2018-11-03
- ^ a b c L. Golob, N. Jonathan, A. Morris, M. Okuda, K.J. Ross (1972), "The first ionization potential of the methyl radical as determined by photoelectron spectroscopy". Journal of Electron Spectroscopy and Related Phenomena, volume 1, issue 5, pp. 506–508 doi:10.1016/0368-2048(72)80022-7
- ^ R.B. Sharma , N.M. Semo , W.S. Koski (1987), "Dynamics of the reactions of methylium, methylene radical cation, and methyliumylidene with acetylene". Journal of Physical Chemistry, volume 91, issue 15, pp. 4127–4131 doi:10.1021/j100299a037
- ^ Murray J. McEwan, Arthur B. Denison, Wesley T. Huntress Jr., Vincent G. Anicich, J. Snodgrass, M.T. Bowers (1989), "Association reactions at low pressure. 2. The methylium/methyl cyanide system". Journal of Physical Chemistry, volume 93, issue 10, pp. 4064–4068. doi:10.1021/j100347a039
- ^
E.M. Bahati, M. Fogle, C.R. Vane, M.E. Bannister, R.D. Thomas and V. Zhaunerchyk (2009),
"Electron-impact dissociation of CD+
3 and CH+
3 ions producing CD+
2, CH+
and C+
fragment ions". Physical Review, volume 79, article 052703 doi:10.1103/PhysRevA.79.052703 - ^ 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. 0 (16): 920. doi:10.1039/c29690000920. ISSN 0577-6171.