AN INFRARED SPECTROSCOPIC STUDY OF COMPLEX-FORMATION BETWEEN PARA-CRESOL AND PROPIONITRILE

Infrared spectroscopy, together with Factor Analysis and Band Resoluti on techniques have been used to study complex formation in binary mixt ures of p-cresol and propionitrile in the concentration range 0.025 to 0.651 mole fraction of p-cresol. The envelope of the C=N stretching b and of propionitrile in the infared spectrum between 2300 and 2200 cm( -1) was studied. Factor Analysis indicated that there were only two li nearly independent components in the band envelope. The appearance of a pseudo-isosbestic point in the normalized spectra supported this con clusion. For all concentrations, the complex band envelope teas resolv ed into three bands: one assigned to the free propionitrile, a second to a 1:1 p-cresol-propionitrile complex, and a third to an overtone or combination mode of the nitrile, which does not involve C degrees N s tretching. The equilibrium constant K-c for the formation of the compl ex was determined at various mole fractions of p-cresol. The calculate d values of K-c exhibited a strong concentration dependence.