The C2H7+ potential energy surface: a Fourier transform ion cyclotron resonance investigation of the reaction of methyl cation with methane

Autor: J.J. Fisher, Terry B. McMahon, G. K. Koyanagi
Rok vydání: 2000
Předmět:
Zdroj: International Journal of Mass Spectrometry. :491-505
ISSN: 1387-3806
DOI: 10.1016/s1387-3806(99)00231-6
Popis: Fourier transform ion cyclotron resonance experiments have been carried out to probe the nature of the potential energy surface for the reaction of methyl cation (CH3+) with methane (CH4) to give the ethyl cation (C2H5+). Product distributions for reactions of CH3+ and CD3+ with CD4 and CH4, respectively, are found to give a near statistical distribution of ethyl cation products, in good agreement with previous work. When the methyl cation is initially coordinated to HF in the form of a methylfluoronium ion, however, the product distributions are decidedly nonstatistical and are indicative of a reaction which is very nearly thermoneutral. Thermochemical data for relevant species suggest that the reaction is very slightly endothermic. All of the experiments support the intermediacy of a C2H7+ complex in the reactions. Ab initio calculations, in conjunction with all of the experimental data, reveal that there are likely three different stable forms of C2H7+ involved in the potential energy surface for the reaction. One of the forms, a nonclassical C2H5+ coordinated to H2 in a proton bound dimerlike structure, has not previously been considered to play a role in this reaction. The existence of this structure is supported by infrared multiphoton dissociation experiments on C2H7+ previously carried out by Lee and co-workers (J. Am. Chem. Soc. 111 (1989) 5597) and the high pressure mass spectrometric experiments of Hiraoka and Kebarle (J. Am. Chem. Soc. 98 (1976) 6119).
Databáze: OpenAIRE
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