LAUSR

Abstract The assessment of the influence of a halogen atom in the structural, vibrational and conformational properties of o-, m- and p-fluorothioacetanilide derivatives was achieved through different methodologies. For all compounds infrared (FTIR) and nuclear magnetic resonance (NMR) data were obtained; for m-fluorothioacetanilide, FT Raman and GC/MS analysis were additionally performed. The substances now prepared from corresponding aniline derivatives reveal a conformational equilibrium of anti and syn conformers, anti or syn with respect to the N–H and C S bonds, respectively. The evidence of the contribution of each form varies upon experimental conditions of the spectra, being the presence of the least stable alternative evident in room temperature NMR spectra of samples dissolved in CDCl3. The assignment of the signals was supported by quantum chemical calculations and data reported in literature for related compounds. Natural Bond Orbital (NBO) analysis was employed for studying the stability of the conformers upon charge delocalization in order to rationalize dominant electronic effects on each case.