Cryoscopic, infrared spectroscopic and dielectric studies of associated cyclohexanol + benzene mixtures

Abstract

The practical osmotic coefficients and molal activity coefficients of benzene solutions of cyclohexanol over the concentration range 0.02–0.27 mol kg–1 have been determined by the cryoscopic method and infrared spectra of the systems investigated have been recorded in the OH stretching vibration region at 303.65 K. The non-ideal behaviour of the system has been interpreted by the excess Gibbs free energy and on the basis of an associated model including an extended series of multimers. The formation of oligomeric species has been described in term of one independent parameter, i.e. the constant K, which is equal to the stepwise association constants and is related to the self-association constant by βq=K(q–1). From experimental data obtained by the cryoscopic method, the constant K and the concentration of monomer at the lowest concentration studied have been determined by a curve-fitting method, while the concentration of monomer at any definite concentration has been obtained using Bjerrum's integral. From i.r. measurements the fractions of monomer have been obtained for the concentration range studied, and thus the integrated band area of the free OH band of the cyclohexanol monomer has been obtained graphically. In the case of i.r. measurements, the constant K has also been obtained by a curve fitting method.The partial molar volumes, partial molar refraction, partial molar polarization and the apparent dipole moment of cyclohexanol in benzene have been determined at 298.15 K and found to be independent of concentration up to 1.30 mol kg–1. The negative solvent effect on the dipole moment of the cyclohexanol molecule in benzene has been elucidated using Higasi's approach.