Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

The solubility of 2,4-dihydro-5-methyl-2-(4-methylphenyl)-3H-pyrazol-3-one in twelve organic solvents including methanol, ethanol, n-propanol, isopropanol, ethylbenzene, toluene, n-butanol, acetonitrile, ethyl acetate, 1,4-dioxane, cyclohexane and isopentanol were determined experimentally by using the isothermal saturation method over a temperature range from (278.15 to 313.15) K under 101.3 kPa. For the temperature range studied, the solubility of 2,4-dihydro-5-methyl-2-(4-methylphenyl)-3H-pyra zol-3-one in the solvents increased with a rise of temperature. The mole fraction solubility obeyed the following order from high to low in different solvents: isopentanol greater than 1,4-dioxane greater than n-butanol greater than n-propanol greater than ethyl acetate greater than methanol greater than ethanol greater than isopropanol greater than ethylbenzene greater than toluene greater than acetonitrile greater than cyclohexane. The obtained solubility data of 2,4-dihydro-5-methyl-2-(4-methylphenyl)-3H-pyrazol-3-one in the studied solvents were correlated with the modified Apelblat equation, kh equation, Wilson model and NRTL model. The largest values of root-mean-square deviation (RMSD) and relative average deviation (RAD) were 1.35 10 4 and 0.32%, respectively. The RAD values obtained with the modified Apelblat equation were smaller than those with the other three models for a given solvent. So the four thermodynamic models were all acceptable for the systems of 2,4-dihydro-5-methyl-2-(4-methylphenyl)-3Hpyrazol- 3-one in these solvents. Furthermore, the mixing Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient (c1 1 ) and reduced excess enthalpy (HE;1 1 ) at infinitesimal concentration were calculated. The obtained solubility and thermodynamic studies would be very helpful for optimizing the purification process of 2,4-dihydro-5-methyl-2-(4-methylphenyl)-3H-pyrazol-3-one.