Solubility of methylphosphonic acid in selected organic solvents

• The solubility of methylphosphonic acid in seven different solvents have been obtained.
• The interaction energies between solute and solvents were calculated by density functional theory (DFT).
• The results show that the three thermodynamic models agree well with the experimental data.
• The enthalpy, entropy and the free Gibbs energy change of dissolution in different solvents were calculated.

The solubility of methylphosphonic acid in ethanol, n-propanol, i-propanol, acetone, butanone and ethyl acetate was determined by a static analytical method over a temperature range of 288.15–318.15 K. Quantum chemical calculations utilizing Gaussian 09 indicated that solubility of methylphosphonic acid is dependent on solvent polarities and also on interactions with solvent molecules. The modified Apelblat equation, Wilson, nonrandom two-liquid (NRTL), and UNIQUAC models were applied to correlate the experimental data. Finally, the modified van’t Hoff equation was applied to calculate dissolution enthalpy, entropy, and Gibbs energy of methylphosphonic acid in the selected organic solvents.

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