A brief review of Badger-Bauer rule and its validation from a first- principles approach

Understanding the acid-base interactions is important in chemistry, biology and material science as it helps to rationalize materials properties such as interfacial properties, wetting, adhesion and adsorption. Quantitative relation between changes in enthalpy (Delta H) and frequency shift (Delta nu.) during the acid-base complexation is particularly important. We investigate Delta H and Delta nu of twenty-five complexes of acids (methanol, ethanol, propanol, butanol and phenol) with bases (benzene, pyridine, DMSO, Et2O and THF) in CCl4 using intermolecular perturbation theory calculations Delta H and Delta nu of complexes of all alcohols with bases except benzene fall in the range from -14 kJ mol(-1) to -30 kJ mol(-1) and 215 cm(-1) to 523 cm(-1), respectively. Smaller values of Delta H (-2 kJ mol(-1) to -6 kJ mol(-1)) and Delta nu (23 cm(-1) to 70 cm(-1)) are estimated for benzene. Linear correlations are found between theoretical and experimental values of Delta H as well as Delta nu. For all the studied complexes,.H varies linearly (R-2 >= 0.97) with Delta nu concurrent with the Badger-Bauer rule yielding the average slope and intercept of 0.053(+/- 0.002) kJ mol(-1) cm and 2.15( +/- 0.56) kJ mol(-1), respectively.