GENERATION AND ESR-SPECTRUM OF A PERSISTENT AND OXYGEN-INSENSITIVE FREE-RADICAL - 2,7-DI-T-BUTYL-1-PYRENOXY

Oxidation of 2,7-di-t-butyl-1-hydroxypyrene yields persistent and oxyg en-insensitive 2,7-di-t-butyl-1-pyrenoxy radical (2) with the followin g ESR parameters: (a(H)) 0.532, 0.449, 0.430, 0.389, 0.164, 0.110, and 0.095 mT(a(H)), and 2.0037 (g). Radical 2 is isolated as a diamagneti c dimer which, upon dissolution, dissociates into 2 at room temperatur e. The Delta H and Delta S values for the dimer reversible arrow 2 rad ical equilibrium are determined to be 7.2 +/- 2.0 kJ mol(-1) and -35 /- 15 J mol(-1) K-1, respectively. The negative Delta S value is brief ly discussed.