1H NMR spectroscopic and thermodynamic studies of hydrogen bonding in liquid n-butanol + cyclohexane, tert-butanol + cyclohexane, and n-butanol + pyridine mixtures†
Abstract
1 H NMR chemical shifts δOH of the proton in the hydroxyl group of n-butanol and tert-butanol have been measured as function of mixture composition in the binary mixtures n-butanol + cyclohexane, tert-butanol + cyclohexane, and n-butanol + pyridine at 303, 313 and 323 K. In addition the molar excess enthalpy HE of n-butanol + pyridine has been determined as a function of the mixture composition at 298 K using a flow calorimeter. The ERAS (extended real associated solution) model has been applied for describing simultaneously the data of δOH and HE for n-butanol + cyclohexane accounting for self association of n-butanol via hydrogen bonding. The mixture of n-butanol + pyridine was treated similarly using the ERAS model considering self association of n-butanol as well as cross association of n-butanol with pyridine. The results obtained indicate that self association in n-butanol and tert-butanol as well as cross association between n-butanol and pyridine play an important role in these mixtures. The ERAS model is able to describe the dependence of δOH and HE on mixture composition and temperature for all mixtures with a minimum of adjustable parameters providing a realistic insight into the liquid structure of these systems.