Article révisé par les pairs
Résumé : The experimental determination of numerous elementary rate constants in photochlorination reactions had been presented in preceding papers. These permit one to calculate bond dissociation energies, entropics of free radicals and of activated states. Schumacher's results on the photochlorination of ethylene and Howlett and Barton's experiments on the pyrolysis of chlorinated ethanes are re-interpreted. The entropy of activation for hydrogen-abstraction reactions is interpreted in terms of translational electronic, rotational and vibrational terms.