Carbonium ion

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A carbonium ion is a carbocation of the penta- or tetracoordinated nonclassical type such as an ion of the type R5C+ [1].

[edit] methonium

The parent compound methonium or CH5+ is protonated methane and a superacid. This ion exists as a reactive intermediate in interstellar space and can be produced in the laboratory in low concentrations in the gas phase at low temperatures. This compound is considered a CH3+ carbenium ion with a molecule of hydrogen interacting with the empty orbital in a 3-center-2-electron bond. Because the two hydrogen atoms in H2 continuously exchange positions with the three hydrogen atoms in the CH3+ methonium is considered a fluxional molecule. Infrared spectroscopy has been used to obtain information about the conformations of methonium [2] [3]. The IR spectrum of plain methane has two C-H bands from symmetric and asymmetric stretching at around 3000 cm-1 and two bands around 1400 cm-1 from symmetrical and asymmetric bending vibrations. In the spectrum of CH5+ three asymmetric stretching vibrations are present around 2800 - 3000 cm-1, a rocking vibration at 1300 cm-1 and a bending vibration at 1100 1300 cm-1.

[edit] See also

[edit] References

  1. ↑  Stable carbocations. CXVIII. General concept and structure of carbocations based on differentiation of trivalent (classical) carbenium ions from three-center bound penta- of tetracoordinated (nonclassical) carbonium ions. Role of carbocations in electrophilic reactions George A. Olah; J. Am. Chem. Soc.; 1972; 94(3); 808-820. Abstract
  2. ↑  Understanding the Infrared Spectrum of Bare CH5+ Oskar Asvany, Padma Kumar P, Britta Redlich, Ilka Hegemann, Stephan Schlemmer, Dominik Marx , Science 309, 1219 (2005). Abstract
  3. ↑  Quantum Deconstruction of the Infrared Spectrum of CH5+ Xinchuan Huang, Anne B. McCoy, Joel M. Bowman, Lindsay M. Johnson, Chandra Savage, Feng Dong, David J. Nesbitt Science 6 January 2006: Vol. 311. no. 5757, pp. 60 - 63 Abstract
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