NMR AND EPR STUDY OF HYDROGEN-BONDING IN CHLOROANILINES

H-1, C-13 and N-15 NMR chemical shifts were measured for aniline and i ts eight chloro derivatives in weakly interacting solvents. The substi tution of a hydrogen atom by a chlorine atom at the aromatic ring brou ght about the largest deshielding of the substituted carbon; in ortho and para substituted anilines, an increase of shielding of C1 was obse rved (in C-13 NMR) and of neighbouring nitrogen (in N-15 NMR). H-1 che mical shifts DELTAdelta(h) and EPR coupling constants A(N-14) were app lied as a measure of the strength of the NH...O hydrogen bond interact ion with electron donors hexamethylphosphoric triamide, dimethylsulpho xide and nitroxide radical. The values of DELTAdelta(h) and A(N-14) in crease in the series: mono- < di- < trichloroanilines and are the larg est for meta substituted compounds. Electrostatic potential maps (MNDO calculations) show that the NH proton, which is near to the chlorine atom in ortho substituted compounds, has less inclination to bind an e lectron donor molecule.