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
ultravioletphotoionization 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
acetonitrileCH 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]
^
abcGolob, 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.
ISSN0368-2048.
^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.
ISSN0022-3654.
^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.
ISSN0022-3654.
^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.
ISSN1050-2947.
^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.
ISSN0577-6171.