RADICAL RECOMBINATION ENTHALPY - THERMOCH EMISTRY OF THE RINGOPENING OF CYCLOPHANES

By thermolysis of the cyclophanes 1, 5, 8, 11, 14, 18, and 21 in the p resence of NO or O-2 the enthalpy profiles for the ring opening were d etermined from the temperature, NO, or O-2 dependance of the trapping rates of the intermediate diradicals. The experimental enthalpy wells, which varied between 3 and 12 kcal . mol(-1), can be simulated well w ith a reaction forcefield making use of the EVBH method of Malrieu et al. This result gives confidence that also meaningful recombination ba rriers of radicals can be obtained by this method.