Effects of H/D-isotope substitution and temperature on the volume characteristics of tetra-n-butylammonium bromide dissolved in methanol and its D-isotopomers

Densities of Bun4NBr solutions in MeOH, MeOD, and CD3OH were measured at salt concentrations of up to 1.5 solvomolality units (nearly 2.63·10–2 mole fraction) at 278.15, 288.15, 298.15, 308.15, and 318.15 K. The limiting partial molar volumes of Bun4NBr dissolved in these alcohols were calculated. The isotope effects in the volume characteristics of the stoichiometric mixture of ions, [Bun4N+ + Br–], are mainly due to the “vibrational” changes in the solvent structure upon deuteration of different molecular fragments. Structural transformations in infinitely dilute solution of Bun4NBr in methanol are governed by non-specific solvation of the symmetrical Bun4N+ cation.