Studies of Free Radicals at High Pressures. 2. Kinetics for a Variety of Reactions

Article abstract of DOI:10.1021/ja00396a038

Kinetic EPR studies of a variety of free-radical reactions have been carried out at high pressures.Volumes of activation were measured for the β-scission reactions of di-tert-butyliminyl (3.0 +/- 1.0 cm³ mol^-1) and triethoxy-tert-butoxyphosphoranyl (0.2 +/- 1.9 cm³ mol ^-1), for self-reaction of di-tert-butyliminyl (-18.0 +/- 5.3 cm³ mol^-1), and for the rearrangements of 2,4,6-tri-tert-butylphenyl (5.3 +/- 1.7 cm³ mol ^-1) and 2,4,6-tris(perdeuterio-tert-butyl)phenyl (-1.2 +/- 2.0 cm³ mol^-1).These measurements improve the descriptions of the transition states for the variuos reactions and in the case of the phenyl rearrangements provide supporting evidence for a mechanism involving quantum mechanical tunnelling.