Combination Vibration of Neighbouring Molecules in Liquid Hod (IN D2O)

Abstract

Combination vibrations of neighbouring H-bonded molecules show a characteristic absorption band. This band appears in the spectra if H-bonds are formed and vanishes when the H-bonds are broken. Different observations allow the conclusion that the combination v _OH + v _OD in spectra of liquid HOD (in D₂O) may be assigned to a combination vibration (v _OH + v _OD) 2_mol of two neighbouring molecules (HOD and D₂O). The intensity of thisv _OD) 2_mol band was investigated at different temperatures. It results an estimation of the van't Hoff enthalpy change of H-bond formation in liquid water ΔH^o(OH O) = -15.4 ± 1.0 kJ/mole (= -3. 7 ± 0. 2 kcal/mole).