Effect of maltodextrins on the surface activity of small-molecule surfactants

We report on the effect of commercially important polysaccharides (maltodextrins with variable dextrose equivalent (Paselli SA-2, MD-6 and MD-10) on the surface activity at the air–water interface of small-molecule surfactants (sms), possessing different hydrophobic–lipophilic balance ((SSL (Na⁺), the main component is a sodium salt of stearol–lactoyl lactic acid, and PGE (080), polyglycerol ester of C18 fatty acid), and widely used in food products. A marked change of the surface activity of sms was found in the presence of maltodextrins by tensiometry. The combined data of laser multiangle light scattering and mixing calorimetry have suggested that this result is governed by specific complex formation between maltodextrins and sms in aqueous medium. Measurements have been made of the molar mass, the second virial coefficient and the enthalpy of intermolecular interactions in aqueous solutions. The implication of a degree of polymerization of maltodextrins in this phenomenon was shown. The interrelation between the molecular parameters of the formed complexes and their surface activity at the air–water interface has been revealed and discussed.     

Inhibiting activity of complexes of urethanes with variable valency metals

Conclusions The powerful inhibiting action of complexes of variable valency metals with urethanes in the oxidation of ethylbenzene has been revealed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, pp. 479–482, February, 1970.     

Research on 1-azabicyclic compounds

1-(2-Furyl)-3-amino-4,4-dimethylpentane was used to obtain 3-tert-butyl-1,2-dihydropyrrolizine, the catalytic hydrogenation of which over Rh/Al₂O₃ at room temperature gives a mixture of cis- and trans-3,8-H-3-ter-butylpyrrolizidines with predominance of the cis isomer, whereas hydrogenation at 90–100 °C gives a mixture containing the trans isomer as the principal component. The three-dimensional structures of the isomers follow from data on the catalytic hydrogenation and isomerization and the IR, Raman, and PME spectra. A considerable percentage of the trans-fused form is characteristic for cis-3,8-H-3-tert-butylpyrrolizidine.     

Organosilicon and organophosphorus compounds with pseudohalide groups. 2. Reactions of alkoxydimethylsilyl cyanides with chlorides of tricoordinated phosphorus

Reactions of alkoxydimethylsilyl cyanides with some chlorides of tricoordinated phosphorus (phosphorous chlorides) have been studied. It is shown that, depending on the nature of the phosphorous chloride, the chlorine atoms can either be substituted only for cyano groups, or for alkoxy and cyano groups simultaneously. The results obtained in this work clearly show that alkoxydimethylsilyl cyanides are more reactive reagents for attaching cyano groups to a phosphorus atom than trimethylsilyl cyanide.For Part 1, see [1].For a preliminary communication, see [2].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2847–2849, December, 1991.     

Hydrogen-bonded clusters and solvate structures in the supercritical CO2-water-o-hydroxybenzoic acid system: the car-parrinello molecular dynamics

Hydrogen-bonded clusters and solvate structures formed by o-hydroxybenzoic acid (o-HBA) and water in supercritical CO₂ were studied (T = 318 K, 348 K, ρ = 0.7 g/cm³). The atom-atom radial distribution functions, coordination numbers, average numbers of hydrogen bonds for individual atomic groups, and power spectrum were calculated by the Car-Parrinello molecular dynamics. Despite the high polarity of the cosolvent, the hydroxyl group of o-HBA predominantly forms intramolecular hydrogen bond, while hydrogen bonds with water involve only the atoms of carboxyl groups. The temperature effect on the stability of these bonds showed itself in different ways. The intermolecular interactions of o-HBA with carbon dioxide were found to be weaker than those with water. It was established that the Lewis acid-Lewis base interactions between CO₂ and the hydroxyl group of the solute increase with increasing temperature. Instantaneous configurations illustrating the temperature effects on the molecular structures were obtained.     

Calculating the radial distribution functions of supercritical methanol by means of Car-Parrinello and classical molecular dynamics

Radial distribution functions and the average number of hydrogen bonds per methanol molecule under standard, subcritical, and supercritical conditions are obtained via classical molecular dynamics and Car-Parrinello nonempirical molecular dynamics. It is shown that independent methods of modeling yield close results. It is noted that the calculated radial distribution functions agree well with the experimental data only at T = 298 K and P = 0.1 MPa, while at high temperatures and pressures, considerable divergence from the experimental functions known from the literature is observed. It is concluded that both modeling methods reproduce the degree of hydrogen bonding in methanol and its variations depending on the state parameters and correspond closely to the experimental results.     

Computer simulation of the hydrogen bond lifetime and the mechanism of the structural rearrangement of water

The concept of a hydrogen bond lifetime is analyzed in a computer experiment. It is shown that different definitions of the lifetime of a hydrogen bond characterize definite stages in the microdynamics of a liquid. The lifetimes of hydrogen bonds are calculated for water using the TIP4P and TIP4B-HB model potentials. A number of features in the mechanism of the structural rearrangement of the nearest surrounding is determined by comparing them.     

Structure of hydrogen-bonded associates in supercritical water under low and high pressures

The character and structural features of hydrogen-bonded associates in sub- and supercritical water are studied by analyzing distributions of the dipole moments of water molecules at P = 40, 80, and 100 MPa and T = 373–773 K, calculated using Car-Parrinello molecular dynamics. The main types of hydrogen-bonded structures and their changes upon isobaric heating are determined. It is shown that clusters with tetrahedral configurations exist in supercritical water only under high pressure.     

Formation of solvate structures by the <Emphasis Type="Italic">ortho</Emphasis>-, <Emphasis Type="Italic">meta</Emphasis>-, and <Emphasis Type="Italic">para</Emphasis>-isomers of hydroxybenzoic acid in supercritical fluid

The solvate structures formed by the ortho-, meta-, and para-isomers of hydroxybenzoic acid (o-HBA, m-HBA, and p-HBA) with a polar co-solvent (methanol at a concentration of 0.030 and 0.035 mole fractions) in supercritical carbon dioxide at a constant density of 0.7 g/cm³ and temperatures of 318 and 328 K have been studied by the classic molecular dynamics. It has been determined that a stable hydrogen-bonded complex with the co-solvent forms via the hydrogen of the carboxyl group for all isomers. The probability of this complex existence is high at all temperatures and concentrations. In the o-HBA molecule, the other functional groups are engaged in the intramolecular hydrogen bond, but not involved in interactions with methanol. It has been found that m-HBA and p-HBA can be involved in hydrogen bonds with methanol via hydroxyl hydrogen and oxygen atoms; they are characterized by the presence of one more co-solvent molecule (rarely, two molecules) in their solvation shell and intermittent formations/breakages of hydrogen bonds via other functional groups. These bonds are far less stable, and their formation is sensitive to change of temperature and co-solvent concentration. It has been concluded that the degree of selective solvation of m-HBA and p-HBA by co-solvent molecules is approximately the same, but the rate of structural rearrangements in the nearest environment of m-HBA is higher than that of p-HBA.