Investigation of intermolecular interactions in solutions by means of millimeter-wave spectroscopy 4. Negative and positive hydration in aqueous solutions of urea

Khurgin, Yu. I.; Kudryashova, V. A.; Zavizion, V. A.

doi:10.1007/bf00960649

Cited by 8 publications

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“…The same does for solution of U in EG (C p,2 o ≈ 199 J mol −1 K −1 ). 8 On the other hand, despite a destructing phenomenon of "urea's negative hydration", [48][49][50]93 it is agreed upon now that the introduction of U molecules into the aqueous medium does not induce any substantial distortion of the solvent H-bonding network around the solute amino groups. 8,32,106,107 Moreover, in contrast to hydrophilically hydrated carbonyls of U, there is suggestion on a similarity of hydration of urea's NH 2 groups and hydrophobic species.…”

Section: Experimental Densities and Apparent Volumesmentioning

confidence: 99%

“…As for the (FA + TMU) system, we have found a single work by Maharajh, in which the density measurements of mixtures have been performed over the whole composition range at T = 298.15 K (as is a customary). In turn, the literature data on volumetric characteristics of aqueous U and TMU are rather conflicting in the nature of solute–solute interaction, − and the influence of U on water structure is not yet clearly understood. ,,,− …”

Section: Introductionmentioning

confidence: 99%

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Solutions of Urea and Tetramethylurea in Formamide and Water: A Comparative Analysis of Volume Characteristics and Solute–Solute Interaction Parameters at Temperatures from 288.15 to 328.15 K and Ambient Pressure

Ivanov¹,

Кустов

Lebedeva³

2019

J. Chem. Eng. Data

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Densities of urea (U) and tetramethylurea (TMU) solutions in formamide (FA) and water with a solute molality of up to ∼2 mol kg–1 were measured at T = 288.15, 298.15, 308.15, 318.15, and 328.15 K and p = 99.6 kPa. All experiments were performed using a precision vibrating U-tube densimeter at measuring uncertainty not exceeding 0.03 kg m–3. Standard partial and excess molar volumes as well as volume-related parameters of solute–solute interactions for U and TMU in both solvents under comparison were computed. The derived results were discussed on the assumption that FA, like water or ethylene glycol (EG), is a solvent having a capability to form the spatial hydrogen-bonding network, inducing effects of solvophobic solvation. It was found that a structure-compression effect during the solvation of TMU in FA becomes somewhat enhanced with increasing temperature. In turn, the process of forming the “solvation complex” of U in FA is accompanied already by structure loosening at temperatures higher than T = 288 K. The same goes for both (EG + TMU) and (EG + U) systems, too, but the “loosening effect” in the last case appeared at T > 308 K only. Similarly to aqueous solutions, the temperature has a differentiating effect on trends of changing in both the standard partial molar expansibility of U and TMU and volume coefficients of the U–U and TMU–TMU pair interactions in FA as well as EG. The data obtained here confirm the fact that the solvophobity of TMU in water is markedly stronger pronounced than it occurs in FA and EG media. Herewith, the previous conclusion that, in a thermochemical sense, the solvation behavior of compared ureas in FA is more “waterlike” than in liquid EG is overall true for the solute TMU only.

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