Evaluation of Hydrogen-bonding Ability of Alcohols and Their Mixtures with Water

Abstract

Raman spectroscopy has been applied to study the hydrogen-bonding donating and accepting abilities of supercritical alcohols and their mixtures with water. The hydrogen-bonding donating ability was evaluated by the Raman shift of C=O stretching vibration of benzophenone. The hydrogen-bonding accepting ability was evaluated by the Raman shift of NH₂ stretching vibration of p-nitroaniline. The solvent density dependences of these two properties were similar to each other, and even near the critical density of the solvent, the solvent shows substantial hydrogen-bonding abilities. The effect of water, however, was opposite for these two cases. The addition of water strengthened the hydrogen-bonding donating ability of the solvent, while the addition of water weakened the hydrogen-bonding accepting ability of the solvent. Molecular dynamics simulation was performed to evaluate the hydrogen-bonding between pNA and solvent, and the selective solvation was discussed.