Apparent Molar Volume and Viscosity of N-Methylpyridinium Iodide and Its Methyl-Substituted Derivatives in Water

Abstract

The apparent molar volume and the viscosities of N-methylpyridinium iodide and its methyl derivatives in water at 25, 30, 35, and 40 °C are reported. The apparent molar volumes obey Masson’s equation. The φv° and Sv* values indicate strong ion–ion interaction in water. φv° is linearly related to temperature. The relative viscosity data of these salts obey Jones–Dole and Vand equations well. The A and B values of Jones–Dole equation and Q values of Vand equation suggest greater solvation in case of NMPI and the β-CH3 salt and greater ion–ion interaction in case of α-CH3 and γ-CH3 salts. The data have been discussed in terms of hydrophobic hydration and solvent shared ion pairs. The free energy of activation for viscous flow are almost equal for these salts. The importance of A, B, B+, and Q to the study of the solvent structure is discussed.