The noncoincidence effect of the C=O stretching vibration of acetone in acetone/water mixtures

The dilution study of acetone in water shows that Maniso(C=O) and Miso(C=O) shift to lower wavenumbers quite linearly with dilution, the total shift being around –10 cm-1 for Miso(C=O) and –15 cm-1 for Maniso(C=O). This demonstrates that for acetone molecules the water environment is more attractive than acetone itself, and even more than a DMSO environment. On the other hand, the concentration dependence of NCE(C=O) of acetone in water shows a slight downward curvature a fact which would suggest if compatible with the fact that water has an electric dipole moment smaller than that of acetone, while being that of DMSO higher than that of acetone. The experimental results (including the band shapes of the isotropic and the anisotropic component) can be satisfactorily reproduced in MD simulations using the TIP5P water model.