Infrared spectra of ortho-substituted acetanilides: Vicinal effects and conformation

摘要

The infrared spectra of twenty-two ortho-substituted acetanilides (la-lv) in CCl4 and CHCl3 were measured in the region of the C=O and NH stretching vibrations and compared with those of para-substituted acetanilides (2a-2i). The wave numbers of the C=O stretching vibrations were analyzed using empirical substituent constants and single- and multiparametric correlations. On the basis of the above approaches, the separation of the polar effects into inductive, field, resonance, and steric components has been assessed for the ortho-substituted series. For compounds containing polar substituents with double bonds, specific vicinal effects caused by intramolecular hydrogen bonding have been observed. The conformations of ortho-substituted acetanilides la-lv were studied by both infrared spectroscopy and AMI calculations.