INFRARED SPECTROSCOPIC STUDY OF ACETONITRILE IN AQUEOUS INORGANIC SALT-SOLUTIONS AND COMPARISON WITH RELATED POLYACRYLONITRILE SOLUTIONS

The infrared spectra of acetonitrile (CH3CN) have been obtained in the v(CN) stretching region for the pure liquid, in water and in aqueous salt solutions of sodium thiocyanate, sodium iodide, lithium iodide, calcium iodide and zinc chloride. The CN absorption bands of acetonitrile in aqueous inorganic salt solutions were very similar in character to those found in aqueous solutions of poly(acrylonitrile-co-vinyl acetate) containing inorganic salts. The effect of the salt solutions on the v(CN) stretching absorptions can be divided into three types; (i) solutions containing NaSCN and NaI which cause a shift in the v(CN) absorption band relative to that in pure CH3CN, with delta-v = +6 cm-1, (ii) solutions containing ZnCl2 which give rise to two absorption bands with shifts of delta-v = +6 and +60 cm-1, and (iii) those containing LiSCN and CaI2, which also produce two absorption bands but with shifts of delta-v = +6 and +22 cm-1. The spectral data are critically compared with those previously obtained for poly(acrylonitrile-co-vinyl acetate) under a similar range of conditions.