SPECTRAL AND KINETIC MEASUREMENTS ON A SERIES OF PERSISTENT IMINOXYL RADICALS

A series of new iminoxyl radicals, Et3C(C=NO.)Bu-tert (I), tert-C5H11( C=NO.) Bu-tert (2), (tert-C5H11)(2)C=NO. (3), Et3C(C=NO.)Ph (4), PhCH2 CMe2(C=NO.)Bu-tert (5), PhCMe2(C=NO.)Bu-tert (6) and Me2CH(C=NO.)C5H11 -tert (7), was characterized by EPR and in some cases visible spectra and decay kinetics in solution. Isolation of 1H and utyl-4,4-diethyl-5 -methyl-4,5-dihydro-5-isoxazolol (9) among the decomposition products of 1 was consistent with a previously unrecognized mode of iminoxyl re action in which the initial step is an internal beta-H abstraction, Mo lecular orbital calculations on H2C=NO. indicate a C-N-O angle of abou t 140 degrees and a 10 kcal mol(-1) barrier to inversion. Rate constan ts for the reaction of tert-Bu2C=NO. (8) with a series of olefins were measured. (C) 1997 John Wiley & Sons, Ltd.