Hindered planar conformation of ortho disubstituted N-sulfinyl-benzenamines: non-planar syn structures prevalence over anti R-N=S=O configurations

Ortho disubstituted N-sulfinyl-benzenamines were studied by spectroscopic a nd theoretical methods. Both ethyl and isopropyl substituents promote remov al of the N=S=O group from the symmetry molecular plane. These R-N=S=O comp ounds maintain their syn configuration with respect to the C-N single bond and S=O double bond. The analysis of the pre-resonance Raman spectra reveal s enhancement of bands involving at least a pi --> pi* transition in the N= S=O chromophore. The extension of the enhancements precludes interaction wi th the benzenic ring through pi delocalisation and/or benzenic ring transit ions. (C) 1999 Elsevier Science B.V. All rights reserved.