Volumetric and Viscometric Approach to Understand Molecular Interactions of Tetra-n-propylammonium Bromide in Water and Aqueous Mixtures of 1,3-Dioxolane and Tetrahydrofuran at Different Temperatures

The present investigation is made on a surface-active organic ammonium halide, tetra-n-propyl ammonium bromide dissolved in water and (water + 1,3-dioxolane and tetrahydrofuran). Volumetric and viscometric parameters are computed from experimentally measured density and viscosity data. Experimental temperatures range from 298.15–313.15 K with 5 K intervals. Apparent molar volume, Vφ , and partial molar volumes, Vφ⁰ thus calculated from density ( ρ ) values are used to predict ion–ion and ion–solvent interactions. Magnitudes of partial molar expansibility, Eφ⁰ and Hepler’s constant (∂2 Vφ⁰ /∂T2)p are indicative of the structure making/ breaking behavior of solute and caging effect of solvent. Viscosity coefficients (A_F) and (B_J) are interpreted in terms of ion–ion and ion–solvent interactions. Positive values of Helper’s constant (∂2 Vφ⁰ /∂T2)p and the negative values of ∂ B_J /∂T establish tetra-n-propylammonium bromide (TPAB) as a structure maker. Thermodynamic parameters like (Δ μ ₂^0# ) , (Δ H₂^0,# ) , and (Δ S₂^0,# ) involved in the viscous flow of solution suggest that attending a higher energy transition state is necessary in order to resume the viscous flow.