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 K c for the formation of the complex was determined at various mole fractions of p ‐cresol. The calculated values of K c exhibited a strong concentration dependence.