ABSTRACT
Z,E-isomerization has been investigated for the series of the N-arylthio-1,4-benzoquinonimines using a line shape analysis in the (1)H NMR spectra. Thermodynamic parameters and substituent effects have been analyzed for the isomerization process. It has been shown based on the DFT (B3LYP) calculations that the dynamic transformation for N-arylthio-1,4-benzoquinonimines should be considered as a combination of the two different processes, a rotation about the N-S bond and an inversion at nitrogen via the transition state with the linear C=N-S moiety. The free energies of activation for the isomerization (DeltaG(298 K)) measured experimentally depend on the substitution in the quinonimine moiety and phenyl ring and can be referred either to the inversion of the nitrogen atom or to the hindered rotation about the N-S bond.
