Solubility Measurement, Correlation, and Thermodynamic Analysis of N-Acetyl-l-leucine in 12 Pure Organic Solvents from 283.15 to 323.15 K

The solubility of N-acetyl-l-leucine in 12 mono organic solvents (methanol, ethanol, n-propanol, 2-propanol, 1-butanol, isobutanol, 2-butanol, methyl acetate, ethyl acetate, propyl acetate, acetone, and acetonitrile) was determined by the gravimetric method over the temperatures ranging from 283.15 to 323.15 K at 0.1 MPa. The solubility of N-acetyl-l-leucine in each experimental solvent increases with increasing temperature. Moreover, the solubility is an order of magnitude higher in alcohol solvents than in other solvents, which is mainly attributed to the hydrogen bond formation. In addition, the experimental solubility data are correlated by three models, including the modified Apelblat equation, λh equation, and the nonrandom two-liquid (NRTL) model. All of the average relative deviation % values are less than 3.72%, which indicates that the three models have satisfactory correlations. Furthermore, the mixing thermodynamic properties of N-acetyl-l-leucine in 12 mono solvents including ΔmixG0, ΔmixH0, and ΔmixS0 are calculated based on the NRTL model, indicating that the mixing process was spontaneous.