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

Fourier transform IR spectroscopy, together with factor analysis and b and resolution techniques, has been used to study complex formation in binary mixtures of m-cresol and propionitrile in the concentration ra nge 0.1-0.9 mole fraction of m-cresol. The profile of the C=N stretchi ng band of propionitrile in the IR spectrum near 2250 cm(-1) was studi ed to determine the nature of the association. Factor analysis indicat ed that there were only two linearly independent components in the ban d envelope. The appearance of a pseudo-isosbestic point in the normali zed spectra supported this conclusion. For all concentrations, the C=N stretching band envelope was resolved into three bands: one assigned to free propionitrile, a second to an m-cresol-propionitrile complex a nd a third to an overtone or combination mode of the nitrile which doe s not involve C=N stretching. The results indicated the formation of a 1:1 complex. The equilibrium constant K-c for the formation of this c omplex was determined at various mole fractions of m-cresol. The calcu lated values of K-c exhibited a strong concentration dependence.