Shape analysis along reaction paths of ring opening reactions

Abstract

In this work we analyze the interrelations between potential energy changes and molecular shape changes along the reaction paths for a series of ring-opening reactions. The processes studied correspond to the opening of the four-member rings of 1,2-dioxete, 2H-oxete, 2H-thiete, and 1,2-dithiete, which recently have been given considerable attention in the literature. We describe the molecular shape in terms of a continuum of fused-sphere surfaces, which are characterized by using molecular topological methods. The four processes cover a range of reaction enthalpies from largely exothermic to almost thermoneutral. The similarity between the configurations found along the reaction path is assessed quantitatively in terms of parameters associated with the molecular shape and the path itself. We find a correlation between the value of the energy barriers (and reaction enthalpies) and the similarity parameters. The correlation is comparable to that found in the case of various other processes, such as torsional changes, collisions, and intramolecular atom displacements or shifts. The results are in line with the intuitive correlations expected from the Hammond postulate.