Historical perspective on: RRKM reaction rate theory for transition states of any looseness [Volume 110, Issue 3, 28 September 1984, Pages 230–234]

Abstract

The field of unimolecular reactions and bimolecular recombination processes [1], [2], [3], [4], [5], [6], [7] and [8] has undergone a number of changes during the past 90 or so years. In the middle 1920s, the theories of Hinshelwood, Rice/Ramsperger, and Kassel were developed at a time when little was known about potential energy surfaces. So the theory was phrased in terms of the sharing of energy in a dissociating or isomerizing molecule among ‘squared terms’, meaning the kinetic energies and potential energies of harmonic molecular vibrations. In fact, in those early days, before the development of gas phase free radical mechanisms for unimolecular reactions, the latter were assumed to be non-free radical dissociations. They were realized, in the 1930s, to be, largely, dissociations, followed by subsequent free radical reactions. (Hinshelwood received the Nobel Prize for this free radical work.) On the theoretical side, transition state theory emerged in the mid 1930s, and in 1951–1952 I was involved in blending it and RRK theory together [9] and [10], resulting in what later became known as RRKM theory.