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An EPR investigation of the kinetics of the exit, k[sup -], and entrance, k[sup +], processes in micelles of sodium dodecyl sulfate, hexadecyltrimethylammonium bromide and polyoxyethylene(6)decanol of a family of para-substituted benzyl tert -butyl nitroxides and para-substituted benzyl hydroxyalkyl nitroxides is reported. The inclusion of nitroxide probes in the hydrophobic environment of the micelle gives rise to a reduction of the value of both nitrogen and β-proton splittings, with the result that the resonance fields for the M[sub I](2H[sub β]) = ±1lines of the free and included species are significantly different. The rate constants were obtained by analyzing the EPR line shape variations as function of surfactant concentration and temperature. The experimental value of k[sup +] obtained from the study of benzyl tert-butyl nitroxide indicates that the association reaction is very close to being controlled by diffusion. The value of the exit rate, k[sup -], instead, depends on the probe hydrocarbon chain length. A comparison of our results with those obtained by luminescence quenching techniques is also reported. [ABSTRACT FROM AUTHOR]

The O-H bond dissociation enthalpy (BDE) of 3,5-dimethylphenol has been determined, by using the EPR radical equilibration technique, as 362.5 ± 1.5 kJ/mol. This value is 7 kJ/mol smaller than that of phenol, this indicating that alkyl substitution of the meta hydrogens of phenol induces a weakening of the O-H bond, in contrast with what was reported in a recent calorimetric study. [ABSTRACT FROM AUTHOR]

Provides information on the sixth General Meeting of Gruppo Italiano di Risonanza di Spin Elettronico held in Urbino, Italy on September 17-20, 2001.