Solvent effects on the infrared spectra of anilines-V: Anilines with no ortho substituents

Abstract

N-H stretching frequencies of seven primary aromatic amines in carbon tetrachloride solution have been measured in the presence of varying mole fractions of hydrogen bond acceptor. The first hydrogen bond between amine and solvent causes a much larger shift in the symmetric N-H stretching frequency than in the antisymmetric, while the second hydrogen bond has a large effect on the antisymmetric frequency and almost none on the symmetric. The frequency shifts show excellent correlation with the Hammett constants of the aniline ring substituents. Fermi resonance and bulk solvent effects on the N-H stretching frequencies are identified in some instances.