Solubility and Hansen Solubility Parameters of l-Glutamic Acid 5-Methyl Ester in 12 Organic Solvents from 283.15 to 323.15 K

Abstract

In this study, the quantitative mole fraction solubility of l-glutamic acid 5-methyl ester in 12 individual organic solvents (water, methanol, ethanol, 1-propanol, 2-propanol, acetone, 2-butanone, acetonitrile, 1,4-dioxane, ethyl acetate, n-hexane, and dichloromethane) were reported. The solubility determinations were performed via the gravimetric method in the temperature range of T = 283.15–323.15 K, except for dichloromethane at T = 283.15–308.15 K. The powder X-ray diffraction test was used to research the polymorphism of l-glutamic acid 5-methyl ester, and the consequence shows that there is no crystal transformation in the process of solubility measurement; besides, it is found that the mole fraction solubility of l-glutamic acid 5-methyl ester is positively correlated with the experimental temperature in the tested solvents. The measured data are observed the highest in water (0.042569), followed by methanol (0.001379), 1,4-dioxane (0.000331), acetone (0.000221), ethanol (0.000212), ethyl acetate (0.000145), 2-propanol (0.000144), n-hexane (0.000132), 1-propanol (0.000116), 2-butanone (0.000107), acetonitrile (0.000034), and dichloromethane (0.000024) at “T = 298.15 K”. Different properties of the chemicals, including solvent polarity, hydrogen bond, molecular structure, and Hansen solubility parameters, were summarized to analyze the solubility behavior of l-glutamic acid 5-methyl ester in the investigated neat solvents. The results show that the mole fraction solubility of l-glutamic acid 5-methyl ester in the selected solvents is a complicated phenomenon affected by multiple factors. Two thermodynamic models, which are the modified Apelblat model and the Yaws model, were employed to correlate the experimental solubility, and the fitting results of the two models were both well. Moreover, the AIC values and the Akaike weights of the two models were computed to assess the fitting level.