Fourier transform infrared spectrometric study of the interaction between hexa-2,4-dienylideneisopropylamine and 3-phenylprop-2-enylideneisopropylamine with model proton donors Part I. Thermodynamic parameters, ?C==N and ?OH stretching vibrations

Abstract

The interaction of hexa-2,4-dienylideneisopropylamine and 3-phenylprop-2-enylideneisopropylamine with phenol derivatives (pKa = 10.30−0.4) was investigated in solution by Fourier transform IR spectrometry. The influence of hydrogen bond formation on the frequency and intensity of the CN stretching vibration is discussed. The thermodynamic parameters for the normal hydrogen bonds and for the proton transfer complexes were determined; 50% proton transfer is achieved for ΔpKa values of about 2 for both imine systems. The lowest OH stretching frequencies corresponding to a delocalized proton are observed at about the same ΔpKa values.