On the conformation of the inversion state in the thermal E,Z isomerization of aromatic azomethines

Abstract

Ab initio STO-3G calculations with full geometry optimization on substituted formaldehyde-, pyrazolone- and hexafluoroacetone-anils indicate different conformations of the linear inversion state in the thermal E,Z isomerization of aromatic azomethines dependent on the extent of push-pull conjugation in the molecular systems; based on this fact, an explanation of Hammett plot deviations from linearity found for special azomethines becomes possible without the assumption of a competition between the inversion and rotation mechanism in the E,Z isomerization.