Volumetric and Viscometric Studies of Paracetamol in Aqueous Solution of Alcohols at Different Temperatures

Abstract

Paracetamol in presence of Water, 80% Water + 20% n-Propanol, 20% Water + 80% n- Propanol, 80% Water + 20% n-Butanol and 20% Water + 80% n-Butanol were studied through the measurement of viscosity and density at different temperatures (298.15K to 323.15K) with an interval of 5K. The results were discussed on the basis of structure making and breaking mechanism of paracetamol in aqueous and aqueous alcohols solution under experimental conditions. The apparent molar volumes increase with the rise of concentration of paracetamol for all the studied systems indicating the structure making interaction for all the studied systems. The limiting apparent molar volume (φv 0) or partial molar volume at infinite dilution of paracetamol are positive and increase when paracetamol content in the solvents increase. The positive values of transfer apparent molar volume (Δφv)tra suggest the structure making ability through hydrophilic-hydrophilic interactions between polar groups of paracetamol and polar groups of alcohols-water. The values of limiting apparent molar volume expansibilities (Eφ0) are positive and the values of (δEφ0/δT)p are small which suggest the structure making property in these systems. Viscosities increase with increasing of paracetamol concentration. The B-coefficients for paracetamol in the studied systems are positive and thus suggest the presence of solutesolvent interactions or structure making properties. The values of D-coefficient are mainly negative showing weak solute-solute interactions. The changes of free energies (ΔG#) are increased with the increase of concentration of paracetamol and the values are positive for all the studied systems. It is also seen that the changes of free energies (ΔG#) of paracetamol in aqueous solutions of n-Propanol and n-Butanol increase very slowly with increasing solute concentration and decrease with increasing temperature. The values of enthalpy of activation (ΔH≠) indicate the interaction presence in solute-solvent through H-bonding. The entropy (ΔS≠) values are positive for all the systems and decrease with increase of paracetamol concentration. The positive values of change of chemical potential (Δμ1 ≠ - Δμo≠) for all studied show greater contribution per mole of solute to free energy of activation for viscous flow of the solution and are good agreement with the values of B-coefficient showing structure making properties between solute and solvent.