The pressure effect on strained transition states. Correlation between strain and volume of activation: mechanistic and synthetic involvements

Abstract

This paper considers the description of the pressure effect on strained transition states and proposes a kinetic formalism based on the concept of steric or strain volume of activation with a view to devising models allowing the calculation of structure effects on the position of the transition state along the reaction coordinate. The applicability of the equation is examined for several reactions (Menshutkin, solvolysis and hydrogen transfer). When steric or strain factors operate in a given reaction the pressure effect is more marked than in an unhindered analogue. Possible consequences of this phenomenon are considered, with special emphasis on mechanistic and synthetic implications at high pressure.