Pattern of separatrices and intrinsic reaction coordinates for degenerate thermal rearrangements

TLDR: In this paper, a structurally stable model of the standard adiabatic gradient field of the potential energy surface for certain pericyclic reactions is derived, which are not subjected to the principles of orbital isomerism or to the Woodward-Hoffmann rules.

Abstract: A structurally stable model of the standard adiabatic gradient field of the potential energy surface for certain pericyclic reactions is derived. These reactions are not subjected to the principles of orbital isomerism or to the Woodward-Hoffmann rules. Use is made of a principle established by Ariel Fernandez and Oktay Sinanoglu which precludes direct meta-IRC connections between transition states. It is shown that Jahn-Teller isomers of the singlet biradicals involved in the process are not interconvertible since the biradical configuration is not a transition state but a critical point with Hessian matrix with two negative eigenvalues. The topological features of the PES obtained by combinatorial methods are in full agreement with earlier results obtained from MINDO calculations.