Raman spectroscopic study of complex formation between p-cresol and propionitrile

Raman spectroscopy, together with factor analysis and band resolution techniques, was used to study complex formation in binary mixtures of p‐cresol and propionitrile in the concentration range 0.025‐0.651 mole fraction of p‐cresol. The envelope of the C  N stretching band of propionitrile in the Raman spectrum between 2300 and 2200 cm−1 was studied. Factor analysis indicated that there were only two linearly independent components in the band envelope. The appearance of a pseudo‐isosbestic point in the area normalized spectra supported this conclusion. For all concentrations, the C  N stretching band envelope was resolved into three components. These were assigned in turn to the free propionitrile, a 1:1 p‐cresol‐propionitrile complex and an overtone or combination mode of propionitrile which does not involve C  N stretching. The equilibrium constant Kc for the formation of the complex was determined at various mole fractions of p‐cresol. The calculated values of Kc exhibited a strong concentration dependence.