D2O−H2O solvent isotope effects on the enthalpies of bicaret hydration and dilution of its aqueous solutions at different temperatures

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

“…4.8 and 4.9 cm 3 Á mol À1 , according to the data of table 5) for both solutes within the temperature range studied. The fact of greater changing of E o p;m (1,3-DMGU) with increasing temperature may be primarily due to faster disruption of heterocomponent H-bonded local structures (hydration complexes), which are formed at the expense of proton-donor (NH and HCACH) and proton-acceptor (C@O) groups of the solute molecules [20,[24][25][26][27][28][29]46,47]. As for aqueous 1,3-DEGU, the possibility of forming such hydrogen bonds is to be sterically hindered, on the whole, due to the more bulk-branched alkyl substituents in the molecule of this tetra-N-substituted glycoluril.…”

“…So far, perhaps, only the molecular structure of mebicar and some thermodynamic and physicochemical characteristics of its aqueous (in H 2 O and D 2 O) solutions have been comprehensively studied [14,[20][21][22][23][24][25]. There are also several works [26][27][28][29] in which aqueous solutions of other glycolurils including achiral 1,3-dimethyl-and 1,3-diethyl-derivatives have been investigated densimetrically or calorimetrically. The interest in glycoluril alkyl-N-derivatives stems primarily from the desire to study the structure-packing transformations they cause in the surrounding water.…”

“…The effect is associated with the competition between the contributions arising from the hydrophobic and hydrophilic parts of a solute molecule in the course of hydration and to their joint action on the water structure. Having the hydrophilic >C@O group and N-sited hydrophobic alkyl radicals or/and hydrogen atoms in each of the conjugate molecular five-membered rings, being connected by the grouping [>C(H)AC(H)<] or glyoxalic bridge (figure 1), such a solute can be regarded as a simplified model compound for biopolymers that exhibit complex interactions with water [20,24,29].…”

Standard Volumetric Properties of Tetra-N-ethylglycoluril (Bicaret) in Ordinary and Heavy Water at Temperatures from (278.15 to 318.15) K and Ambient Pressure

“…When the specified glycolurils are subjected to dissolution in water, this leads to the fact that the molecules of bicaret are hydrated more strongly than those of its tetra-N-methylated analogue. 25 Herewith, unlike the mebicar (for which the standard molar enthalpy of solution, Δ sol H 2 o , is positive), 26−28 the hydration of bicaret (where Δ sol H 2 o < 0) is treated as a prevailingly hydrophobic process. 25 One would expect that the existing differences in the hydration behavior of mebicar and bicaret will be reflected on the peculiarities of structure-packing transformations in the aqueous environment.…”

“…25 Herewith, unlike the mebicar (for which the standard molar enthalpy of solution, Δ sol H 2 o , is positive), 26−28 the hydration of bicaret (where Δ sol H 2 o < 0) is treated as a prevailingly hydrophobic process. 25 One would expect that the existing differences in the hydration behavior of mebicar and bicaret will be reflected on the peculiarities of structure-packing transformations in the aqueous environment. The latter should be manifested in the volumetric properties of both a solute and a binary solution on the whole.…”