Apparent Molar Volumes and Expansibilities of Thiourea, 1,3-Dimethylurea, and 1,3-Dimethylthiourea in Water at Temperatures from T = (278.15 to 318.15) K and Atmospheric Pressure

Abstract

Densities of dilute aqueous solutions of thiourea, 1,3-dimethylurea, and 1,3dimethylthiourea were obtained using the Anton Paar DMA 5000 M vibrating-tube densimeter. The apparent molar volumes and expansibilities (down to infinite dilution) were computed from the measured density data. The experiments were performed at five temperatures from (278.15 to 318.15) K and atmospheric pressure. A comparison of volumetric and some other thermodynamic changes caused by the N,N′-methylation in thiourea and urea molecules are discussed.

Standard molar volumes and expansibilities of 1,3-alkyl-N-substituted achiral glycolurils in water at T=(278.15 to 318.15)K and p=0.1MPa: A comparative analysis

“…Both structure-making and structure-breaking hydration effects in the considered binary solutions must be stronger at lower temperatures [24,39,43,45]. This explains largely why the v 22 values become decreasingly negative when the temperature increases.…”

“…According to the data on ð@v 22 =@ðT À hÞÞ p ð@E p;/;m =@c aqm Þ p h i placed in table 5, an increase in the 1,3-DMGU or 1,3-DEGU content causes [38,39]). …”

“…The same conclusion was drawn previously [20,[23][24][25]47,49] when studying the thermodynamic effects of mebicar hydration. It should be borne in mind also that the sign at ð@E 1 p;/;2 =@TÞ p presumably does not sufficient condition to identify the enhancement of solvent structure or its destroying [39]. In order to resolve this question, a variety of both thermodynamic and structure properties for the solutes in aqueous media must be considered simultaneously [50].…”

“…Figure 3 shows the temperature-dependent values of packing density, d ¼ V vdw ; m=V o m , which represents the fraction of V o m occupied by the intrinsic volume of a solute [39,51]. The latter quantity is expressed in terms of the Van der Waals volume per one mol, Herewith it is postulated that V vdw;m , being found to be ca.…”

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

“…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.…”