This review summarises the data available in the literature. It also includes the authors' published results of precision densimetric measurements. The research concerns with the physically unusual phenomenon of "thermally activated isobaric partial densification of the structure" (TIPCS) of dissolved water, or its so-called "negative partial molar expandability" (NPEA) in several organic solvents. They contain amphiproton hydroxyl-containing media of three alcohols: methyl alcohol (MA), tertiary butyl alcohol (TBAlcohol), and amyl or pentyl alcohol (TPA), so asprotophilic media of two amines: tert butylamine (TBAmine) and ethylenediamine (EDA). The discussed TIPCS phenomenon, associated with a decrease in the standard (partial at infinite dilution) volume of solvated water with increasing temperature, was discovered about half a century ago in alkanol solutions of H2O and recently - in water-containing media of alkylamines. However, nowadays this extraordinary effect has not yet found its physically based interpretation. It allows ones to predict the possibility of TIPCS occurrence in the binary liquid-phase system specifically selected for the study. Our comprehensive data analysis allowed us to make several inferences regarding the main characteristics of a standard solution of H2O in an organic solvent. They cause extraordinary changes in the volume of the formed solvatocomplex of water under the influence of increasing temperature. Firstly, the energy parameters of the intermolecular interaction (relative affinity) water solvent noticeably dominate over those of the solvent-solvent interaction. Those differences become more evident with increasing temperature. Secondly, a higher rate of thermal expansion of the organic solvent structure in volume (inbulk) is found than influence of temperature on structural packing of the resulting mixed molecular aggregate or water solvates complex. Thirdly, the difference in the parameters of water-solvent and solvent-solvent interactions depends not only on the proton-donor/acceptor properties of the molecules contacting in solution, but also on the configuration of the structural packing of the solvating medium. It determines the nature of steric hindrances to the formation of H-bonds. Therefore, the absolute values of the mentioned parameters of relative affinity at 298.15 K increase in the series: MA << EDA ≈ TBAmine < TPAlcohol < TBAmine. It can indicate a relative strengthening of the specific interaction (mainly through the formation of hydrogen bonds) between the molecules of water and amphiprotonic or protophilic solvent in the above sequence. Indeed, difference in the solvent-solvent and water-solvent hydrogen bonding energies in the discussed liquid media of alkylamines (TBAmine and EDA) and tertiary isomeric alkanols (TBAlcohol and TPA) - with the most evident basicity - turned out to be noticeably larger than in the structural packing of water methanol solution. The ability of the components to specific interactions is quite comparable in those compounds.

Density measurements on solutions of 2,4-dimethyl-6,8-diethyl-2,4,6,8-tatraazabicyclo[3.3.0]octane-3,7-dione or Mebicaret in normal (H2O) and heavy (D2O) water were carried out with a precision of 0.012kg·m−3 using the Anton Paar DMA 5000M vibrating tube densimeter. All experiments were performed within the temperature range between 278.15K and 318.15K (with a step of 10K) at the pressure to be ca. 99.6kPa. The solution aquamolality was ranged from 0.02 to 0.2mol∙(55.51mol of solvent)−1 for each of H/D isotopically distinguishable systems compared. The standard (partial at infinite dilution) molar volumes (V2o) and expansibilities (Ep,2o) of the solute as well as volume-related second virial coefficients (v22) were derived from the data on a solution density. The behavior of solvent isotope effects (IEs) on the considered quantities was described given the structure- and interaction-related peculiarities of the Mebicaret molecule as well as H2O and D2O media. The volume-related interaction characteristics for the solute of interest were discussed using the results of our previous densimetric and calorimetric studies with the participation of similar N-tetraalkylated glycoluril-derivatives.

Densities of H2O and D2O solutions in dimethylsulfoxide, with solute mole fractions ranging up to 0.037, were measured with an uncertainty of 1.5×10−5 g⋅cm−3 at eight temperatures between 293.15 and 328.15 K (with a step of 5 K) under atmospheric pressure using a sealed vibrating-tube densimeter. Apparent molar volumes and isobaric expansibilities (down to infinite dilution) of water isotopologues, as well as excess molar volumes of both solutes and solutions as a whole, were calculated. The temperature-dependent behavior of H2O→D2O solute isotope effects on the studied molar volumetric characteristics was interpreted by taking into account the structural and related interaction peculiarities of the dissolving medium in question.