High-pressure and concentration-dependent studies on C-H---O interactions of binary aqueous mixtures: Formic acid/D2O and acetone/D2O

The C-H---O interactions of formic acid and acetone aqueous solutions were studied under various concentrations. The infrared spectra of acetone/D2O w ere also measured as a function of pressure. The C-H stretching frequency o f formic acid reveals a red-shift with dilution. On the other hand, upon di luting acetone with D2O, the blue-shift with dilution in C-H stretching fre quency was observed. Further high-pressure study provides the experimental evidence for the enhancement of hydrophobic hydration as the sample was com pressed to high-pressure ices, while C-H vibration of acetone, being transf ormed from liquid to high-pressure ice VII, are altered into a band located at similar to 2950 cm(-1). The C-H---O interaction may be a distinct possi bility to understand the band-shape and frequency-shift of the C-H stretchi ng modes of formic acid/D2O and acetone/D2O.