Thermodynamic and theoretical study on hydrogen bonded binary mixtures of isomeric butanols with o-toluidine at T = (303.15 to 318.15) K

Abstract The intermolecular hydrogen bond interactions in the o-toluidine with isomeric butanol (1-butanol, 2-butanol and 2-methyl-2-propanol) binary mixture have been studied both experimentally and theoretically. The speed of sound ( u ), and density ( ρ ) values are measured for binary mixtures of o-toluidine with isomeric butanols over the entire range of a mole fraction at temperatures T = (303.15 to 318.15) K and at atmospheric pressure. The excess molar volume (V m E ), and excess isentropic compressibility (κ s E ) values have been calculated by using the experimental data. In the present study the calculated excess properties are discussed in terms of molecular interactions of binary mixtures. The excess values have been fitted into a Redlich–Kister polynomial equation. The formation of the hydrogen bonds in the binary mixtures of o-toluidine with isomeric butanol dimers are further conformed by high level theoretical calculations. The geometries, bond characteristics, interaction energies and natural bonding orbital (NBO) analysis of the hydrogen bonded complex have been calculated in the gas phase using the density functional theory (DFT) method at the B3LYP/6-311++G(d,p) level theory in a gas phase.