The non-coincidence effect in N,N-dimethylformamide-CCl₄ highly diluted binary mixtures. Experimental and theoretical results

Abstract

We report results on the concentration dependence of the non-coincidence effect in the v(C=O) mode in N,N-dimethylformamide-CCl₄ mixtures. This study has been mainly addressed to the investigation of the experimentally observed sign inversion for this quantity in the low concentration range of chemical mixtures, which is also reported in the literature. We argue that the sign inversion of the non-coincidence effect in N,N-dimethylformamide-CCl₄ mixtures is an artefact originated by the presence of an intrinsic asymmetry which with dilution moves from the blue to the red side of the band. The Logan theory for the thermodynamic state dependence of the non-coincidence effect in chemical mixtures offers a valuable tool for the interpretation of the results in the whole concentration range. Different models are compared and discussed.