QUANTITATIVE PREDICTION OF STRUCTURE-REACTIVITY RELATIONSHIPS FOR UNIMOLECULAR REACTIONS OF UNSATURATED-HYDROCARBONS - DEVELOPMENT OF A SEMI-EMPIRICAL MODEL

A simple theoretical model that has previously been used to make qualitative predictions about substituent and benzannelation effects on the rates of thermal pericyclic reactions has now been shown to give quantitative results for a variety of unsaturated hydrocarbon reactions. These reactions include pericyclic and biradical transformations as well as simple homolytic fission to discrete radicals. Substituent effects on the rates of the pericyclic and biradical reactions can be predicted with an uncertainty (least-squares standard deviation) of ±1.7 kcal/mol, while for homolytic fissions the uncertainty is ±4.4 kcal/mol. Possible contributors to the success of the model are discussed. Applications of the model to the Cope rearrangement, Dewar benzene ring opening, and bicyclo[3.2.0]hept-6-ene ring opening are also considered. © 1979, American Chemical Society. All rights reserved.