High Pressure Kinetic Effects as Mechanistic Probes in Organic Chemistry

Abstract

The high pressure kinetic methodology is a useful tool for the determination and the assessment of mechanisms in organic chemistry. The volume of activation is an indicator of the position of the transition state and, consequently, of the type of mechanism. If accurately determined, it enables the location of polarized, congested or strained transition states and the detection of fine effects (return mechanism in radical decompositions, it-participation in solvolyses, secondary orbital interactions in pericyclic processes, angular hydrogen transfer in ene reactions…). Selected examples are presented: isomerization reactions (aromatization of (Dewar) benzenes, isomerization of azobenzenes), thermal decomposition reactions (thermolysis of radical inhibitors and (3-lactones), substitution and elimination reactions, addition of keto compounds to multiple bonds, pericyclic reactions (sigmatropic shifts, cycloaddition and ene reactions).