Enthalpies and heat capacities of solution of urea and tetramethylurea in water, ethylene glycol and formamide

Solvophobically Driven Complexation of Adamantyl Mannoside with β‐Cyclodextrin in Water and Structured Organic Solvents

“…Unfortunately, the thermodynamic and structural investigations regarding the temperature dependence of nonpolar solute solvation in FMD are particularly scarce. To the best of our knowledge, only the standard solution enthalpies of relatively lipophilic tetramethylurea in FMD have been determined over a wider temperature range (290≤ T [K]≤330) . The reported values were weakly temperature dependent, whereas a strong variation with temperature in water was observed .…”

“…To the best of our knowledge, only the standard solution enthalpies of relatively lipophilic tetramethylurea in FMD have been determined over a wider temperature range (290≤ T [K]≤330) . The reported values were weakly temperature dependent, whereas a strong variation with temperature in water was observed . Such a finding indicates that, unlike in water, no considerable differences in the solvation of the adamantane and cyclodextrin cavity are to be expected in FMD.…”

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

“…Recently, using precision densimetry, we have studied the volume-related pairwise interaction and solvation characteristics for tetramethylurea (TMU) and urea (U) as solutes in ethylene glycol (EG). The latter, being the simplest diol, is one of the organic solvents where a spatial network of hydrogen bonds is tended to the “waterlike” structure transformations around a predominantly hydrophobic solute (such as TMU), a phenomenon defined as the solvophobic solvation. ,,− As it was concluded in ref increasing structure compactness in the “solvation complex” of both TMU and hydrophilic U on going from EG to water can be serving as a corroboration of the fact that the intermolecular hydrogen bonding in aqueous solutions is more stable. ,, At the same time, the structure-making effect in aqueous TMU, being in terms of the solvophobic solvation and pairwise solvophobic interaction, is much more pronounced than it does in the (EG + TMU) system while the structure-breaking effects in the compared solutions of U are differed not as significant. These inferences are in agreement with the results drawn from the calorimetry study performed previously by one of us (A.V.…”

“…The hydrophobic effects including phenomena of hydrophobic hydration and hydrophobic interactions, as is known, are directly associated with the existence of the open three-dimensional hydrogen-bond network in liquid water. Its smallest triatomic molecule forms four H bonds directed along the tetrahedron. − Such a spatially coordinated structure of the aqueous matrix is fairly labile and elastic to accommodate a hydrophobic particle (or moiety) of moderate size, facilitating simultaneously the association of “nonequivalent species” in the regions of defective hydrogen bonding. − The evidence of solvophobic effects in H-bonded nonaqueous (organic) media seems quite speculative. − Formally, to form the spatial network of directed hydrogen bonds in liquids, it is necessary that a solvent molecule has at least two proton donor centers and two proton acceptor ones. , A rather few groups of organic solvents (diamines, amino alcohols, diols, glycerol, etc.) satisfy these requirements.…”

“…Due to the uniqueness of water structure, the above-specified peculiarities of molecular interactions in hydration process are studied most fully by now. In turn, there are only several such investigations for nonaqueous media possessing a similar hydrogen-bonding network. − ,− …”