Intermolecular interactions in aqueous solutions of mebicar

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

“…It can serve as evidence of that both hydrophilic and hydrophobic hydration effects have no any predominating influence on the water structure in the solutions compared. 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].…”

“…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 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 Chiral N-Methyl-Substituted Glycolurils in Water between 278.15 and 318.15 K at Ambient Pressure

“…It may be connected with the different ability of stereochemically distinguishable molecular forms of a glycoluril molecule to hydrogen bonding with water at the expense of proton-acceptor (C = O) groups and proton-donor (N−H and HC−CH) moieties. [6][7][8]32,37,38 One can assume that V 2 o (T) for the chiral (racemic) glycoluril derivatives being studied here, similarly to Nmethyl-substituted acyclic ureas, is influenced by the following: 7,34 (i) an intrinsic contribution from each CH 3 group, (ii) a hydrophobic contribution caused by a molecule sequential methylation, (iii) a hindrance for hydrogen bonding due to an N-methylated position, and a possible decrease in ability to form CO•••H bonds as well. According to the trend of sequential increase in V 2 o expressed by eq 3, the first two of the mentioned effects are to be perhaps most important in the case considered here.…”