ENTHALPIES OF FORMATION AND STABILIZATION ENERGIES OF ALPHA-SUBSTITUTED AND BETA-SUBSTITUTED PROPYL RADICALS - AN AB-INITIO STUDY

Ab initio calculations at various levels of theory (HF/6-31G//6-31G* up to MP4SDTQ/6-31G//MP2(full)/6-31G*) were used to compute the total energies of alpha- and beta-propyl radicals and their parent molecule s. Isodesmic/homodesmic reactions have been studied for the purpose of obtaining theoretical enthalpies of formation of these compounds. Tle choice of the theoretical model as well as the choice of the isodesmi c reaction has been discussed. These data were used to calculate the t hermodynamic stabilization energies of these species according to Lero ys definition, in order to examine the influence of alpha and beta sub stitution on their stability. Homolytic bond dissociation energies (BD Es) were also deduced; it appears that the BDE cannot be used to analy se the substituent effects on the stability of substituted propyl radi cals.