Ultrasonic and computational study of intermolecular association through hydrogen bonding in aqueous solutions of d-mannitol

The estimation of density, viscosity and ultrasonic velocity of aqueous d-mannitol solutions was carried out as functions of concentration (0.1 ≤ m [mol kg− 1] ≤ 1.0) and temperature (303.15 ≤ T [K] ≤ 323.15). The adiabatic compressibility (βad), hydration number (Hn), internal pressure (πi), classical sound absorption (α/f2)class and shear relaxation time (τ) were calculated through ultrasonic experimental method. These parameters have been interpreted in terms of solute-solvent interactions. The quantum chemical calculations were performed to study the hydrogen bonding in interacting complex formed between mannitol and water molecules. Computations have been done by using Density Functional Theory (DFT) method at B3LYP/6-31 + g(d) level of theory to study the equilibrium structure of mannitol, mannitol-water interacting complex and vibrational frequencies. The solution phase study was carried out using Onsager's reaction field model in water solvent. The computed vibrational frequencies are in good agreement with the main features of the experimental spectrum when eight water molecules are considered explicitly with the d-mannitol. The interaction energy (Etotal), hydrogen bond lengths and dipole moment (μm) of the interacting complex were also presented and discussed within the light of solute-solvent interactions.