Hydration of Thiourea and Mono-, Di-, and Tetra-N-Alkylthioureas at Infinite Dilution: A Thermodynamic Study at a Temperature of 298.15 K

Abstract

Molar enthalpies of solution in water, Δsol H m, of thiourea, methylthiourea, ethylthiourea, dimethyl-1,3-thiourea, diethyl-1,3-thiourea, and tetramethyl-1,1,3,3-thiourea were measured at T = (296.84, 302.45, and 306.89) K by isothermal calorimetry. Experimental results were used to derive molar enthalpies of solvation at infinite dilution (i.d.), Δsolv H m ∞, changes in heat capacity due to the solution process, Δsol C p,m ∞, and partial molar heat capacities at i.d., C p,2 ∞, at T = 298.15 K. The methylene group contributions to the enthalpy of solvation and partial molar heat capacity were −4.5 kJ·mol–1 and 88.5 J·K–1·mol–1, respectively, in good agreement with our earlier data for N-alkylureas and the literature data for various homologous series of alkyl-substituted compounds. The contributions of the functional groups to both Δsolv H m ∞ and C p,2 ∞ were derived by employing additive schemes and compared with our earlier data for urea and corresponding N-alkylureas. Hydration behavior at the i.d. of thiourea, urea, and corresponding N-alkyl derivatives were compared and discussed.

Calculation of Five Thermodynamic Molecular Descriptors by Means of a General Computer Algorithm Based on the Group-Additivity Method: Standard Enthalpies of Vaporization, Sublimation and Solvation, and Entropy of Fusion of ordinary Organic Molecules and Total Phase-Change Entropy of Liquid Crystals

“…Mintz et al's [69] paper on the application of the Abraham model mentioned earlier on gaseous solutes dissolved in water and 1-octanol. Further studies were made on N-methylimidazole [70], urea and its derivatives [71][72][73], thiourea and its derivatives [74], carboxamides and their N-substituted derivatives [75][76][77][78], and uracil and its alkyl-, amino-, nitro-and halosubstituted derivatives [79][80][81][82]. Of the accordingly limited number of 465 compounds having experimental enthalpy-of-solvation values in their datalist, 436 have been entered into the calculation of the atom-group parameters, resulting in 61 valid groups allowing the evaluation of the cross-validated prediction of the solvation enthalpy of 373 compounds with a cv-goodness of fit of 0.9546 and a corresponding standard deviation Q 2 of 4.34 kJ/mol as is shown in aggregated manner in Table 3.…”

Volumetric properties of some asymmetrically methyl-N-substituted thioureas in water between (278.15 and 318.15) K at ambient pressure

“…Going from MMTU to 1,3-DMTU and further to 1,1,3-TMTU, the additional\CH 3 groups should further weaken the intermolecular forces and the structure-breaking action of solute molecules [33]. Herewith the structure-making effect is enhanced due to strengthening hydrophobic hydration [13][14][15]. In the case of weakly soluble 1,1,3-TMTU, the occurrence of solute solute hydrogen bonds in water can already be practically excluded.…”

“…1). It may be due to the fact that, unlike the MMTU, the 1,1,3-TMTU molecule does not contain the unsubstituted amino group, whose ability to a strong specific interaction (trough N\H⋯O-bonding) in aqueous solutions of (thio)ureas and amides is well known [13,14,30,[36][37][38][39].…”

“…Unlike aqueous thiourea (TU) and its symmetrically methyl-Nsubstituted derivatives, 1,3-dimethyl-2-thiourea (1,3-DMTU) and 1,1,3,3-tetramethyl-2-thiourea (1,1,3,3-TMTU) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15], the hydration behavior of asymmetrically N-methylated thioureas, 1-monomethyl-2-thiourea (MMTU), 1,1-dimethyl-2-thiourea (1,1-DMTU) and 1,1,3-trimethyl-2-thiourea (1,1,3-TMTU), is far less explored [1,9,13]. Herewith, in these works, the standard molar enthalpies (Δ sol H 2 ∞ ) and heat capacities (Δ sol c p,2 ∞ ) of dissolution were discussed for aqueous MMTU only.…”

“…The methyl-N-substituted thioureas (see Fig. 1), similarly to the related families of ureas, are the simple non-electrolytes with two kinds of functional groups that perturb water in different ways and generate distinct interactions [3,9,13,15]. Hence the volumetric properties for aqueous solutions of such compounds are interesting for knowledge of structure-packing transformations induced by the hydration and other intermolecular interactions [4,14].…”