Solubility determination and thermodynamic modelling of 3,5-dimethylpyrazole in nine organic solvents from T = (283.15 to 313.15) K and mixing properties of solutions

Abstract

Solubility of 3,5-dimethylpyrazole in nine organic solvents including ethanol, isopropanol, n-propanol, 1-butanol, methanol, ethyl acetate, toluene, acetone, acetonitrile was determined experimentally by using the isothermal saturation method over a temperature range from (283.15 to 313.15)K under 101.3kPa. For the temperature range studied, the solubility of 3,5-dimethylpyrazole in the solvents increased with a rise of temperature. In general, they obeyed the following order from high to low in different solvents: 1-butanol>n-propanol>(ethanol, isopropanol, methanol, ethyl acetate, acetone)>toluene>acetonitrile. The acquired solubility data of 3,5-dimethylpyrazole in the studied solvents were correlated by using the modified Apelblat equation, λh equation, Wilson model and NRTL model. The maximum values of root-mean-square deviation (RMSD) and relative average deviation (RAD) were 3.293×10−3 and 2.62%, respectively. The RAD values acquired with the modified Apelblat equation were smaller than those with the other three models for a certain solvent except for the system of n-propanol. Generally, the four thermodynamic models were all acceptable for the systems of 3,5-dimethylpyrazole in these solvents. Furthermore, the mixing Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient at infinitesimal concentration (γ1∞) and reduced excess enthalpy (H1E,∞) were obtained. The solution process of 3,5-dimethylpyrazolewas spontaneous in the studied solvents. The obtained solubility and thermodynamic studies would be very helpful for optimizing the purification process of 3,5-dimethylpyrazole.