| Résumé | Dimethylamino, diethylamino, and diisopropylamino radicals have been generated in the cavity of an epr spectrometer by photolysis of the appropriate tetraalkyltetrazenes and by photolysis of di-tert-butyl peroxide in the presence of the dialkylaminodiethoxyphosphines. The second-order decay of dimethylamino and diethylamino occurs at the diffusion controlled limit, (2 ± 1) × 109 M-1 sec-1. The decay of diisopropylamino is second order at temperatures below ambient (k2 epr ≈ 1.0 X 107 M-1 sec-1) and first order above. For radicals generated from the tetrazene, the first-order process is rather slow and represents thermal decomposition of an intermediate which is probably the cis tetrazene. For radicals generated from the phosphine the first-order process is quite rapid and probably corresponds to a true unimolecular reaction of diisopropylamino radicals, except when the solvent is a good hydrogen donor. 2,2,6,6-Tetramethylpiperidyl radicals were generated from the tetrazene. The decay is first order in hydrocarbon solvents. The variation in the rate constants for decay with hydrocarbon structure, the rate constants in perdeuterated solvents, and product studies show that this reaction is usually a hydrogen abstraction from the solvent. The tetramethylpiperidyl radical is more reactive in abstractions than are peroxy radicals. Tetramethylpiperidyl (aN = 14.66 G, g = 2.0048 in isopentane at 27°) reacts rapidly with oxygen and is converted to the corresponding nitroxide (aN = 15.3 G, g = 2.0064 at -100°). With 17O labeled oxygen this nitroxide has a(17O) = 19.35 G. |
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