| Résumé | The bimolecular self-reactions of two aminium radicals have been studied by kinetic epr spectroscopy. For dimethylaminium in 0.95 M H2SO4-CF3COOH the rate constant for decay is given by 2kt, = 109.5 exp(-5000 ± 1500 cal/RT) M-1 sec-1 and for 2,2,6,6-tetramethylpiperidinium in CF3COOH by 2kt = 109.8 exp(-7600 ± 1000 cal/RT) M-1 see-1. For both radicals 2kt is independent of solvent viscosity (up to 20 cP) but decreases by about one order of magnitude on changing the acidity of the solvent from an H0 value of -3 to a value of -8. This is attributed to a decrease in the activity coefficients of the radicals. Various mechanistic possibilities are considered including hydrogen atom transfer from alkyl to nitrogen, 2R2NH·+*rarr; R2NH2+ + R(R-H)NH+, and from nitrogen to nitrogen, 2R2NH·+ → R2NH2+ + R2N+. |
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