Abstract
The pressure-dependence of the pericyclic rearrangements mentioned in the title uncovers a simple relation between volumes of activation and the number of new cyclic interactions in the transition state. Each new ring formed in the transition state of these pencyclic rearrangements contributes to the volume of activation by roughly −10 to −12 cm3mol−1. Therefore, volumes of activation provide an important information on the geometry of transition states.