Thermodynamics of solubility of thiomalic acid in different organic solvents from 278.15 K to 333.15 K
Introduction
Thiomalic acid (or mercaptosuccinic acid, IUPAC name 2-sulfanylbutanedioic acid, molecular formula C4H6O4S, FW 150.15, CAS Registry No. 70-49-5, shown in Fig. 1) is a dicarboxylic acid containing a thiol functional group. As suggested by its name, it contains an SH group instead of an OH group on malic acid. Salts and esters are known as thiomalates. Thiomalic acid forms the backbone of the pesticide malathion. Mostly thioacids are used in convergent synthesis of peptides and proteins. The thiomalic acid was also used on treatment with suitable nucleophile [1], [2]. Thiomalic acid is an important chiral multi-functional intermediate in organic chemistry and has been widely employed in the synthesis of various biologically active sulfur containing compounds [3] such as antileukemic, spiro[indoline-3,2′-thiazolidine]-2,4′-diones [4], and the anti-microbial [5], [6], and antitubercular [7], 4-thiazolidinones. More recently, it has been used in the synthesis of novel polyanionic inhibitor of HIV and other viruses [8].
In this work, the solubility of thiomalic acid were measured in methanol, ethanol, 2-propanol, 1-butanol, acetone, acetonitrile, and ethyl acetate in the temperature range between 278.15 K and 333.15 K under atmospheric pressure by gravimetric method. The experimental data were correlated with simplified molecular thermodynamic equation, the modified Apelblat equation and the semi-empirical Buchowski–Ksiazczak λh equation. The thermodynamic properties of the solution process, including the Gibbs energy, enthalpy, and entropy were calculated by van’t Hoff analysis.
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Materials
A white crystalline powder of thiomalic acid was purchased from Aladdin Chemistry Co., Ltd. (Shanghai, China) with stated purity of higher 99.5% by mass. Its purity was measured by high performance liquid chromatography in Table 1 (HPLC type Agilent Technologies 1260 Infinity), and its melting temperature was found to between the analytical stirred-flask method determined with digital melting point system (type WRS-1B, Shanghai Precision & Scientific Instrument Co., Ltd.) as between 426.75 K and
Solubility data
The solubilities of thiomalic acid in methanol, ethanol, 2-propanol, 1-butanol, acetone, acetonitrile, and ethyl acetate with the temperature ranging from 278.15 K to 333.15 K are listed in Table 3. For each solvent studied herein, the equilibrium solubility mole fraction of thiomalic acid increased with temperature. It is compared and shown in Fig. 2. At 278.15 K, the mole fraction solubility in these solvents changes from high to low in the order: ethanol > acetone > methanol > 2-propanol > 1-butanol >
Conclusions
The equilibrium solubility data of thiomalic acid in selected organic solvents of methanol, ethanol, 2-propanol, 1-butanol, acetone, acetonitrile, and ethyl acetate over the temperature range of (278.15–333.15) K was investigated by the analytical stirred-flask method. The solubility of thiomalic acid in the organic solvents is a function of temperature and solvent composition. And the solubility of thiomalic acid in all the solvents increases with the raise of temperature and shows the highest
Acknowledgements
This research work was financially supported by the Natural Science Foundation of China (NSFC) (No. 31171644) and the Fund for Agricultural Science and Technology Support Programme of Jiangsu Province in China (No. BE2008399). This research work was also supported by the Fund for Agricultural Science and Technology Independent Innovation of Jiangsu Province in China. (No. CX(12)3060). We thank the editors and the anonymous reviewers.
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