S. B. Bulgarevich

Conformational investigation of N-aralkylpyridinium ions by Cotton-Mouten effect method

Abstract Molar Cotton-Mouton constants and refractions are reported at 298 K for the following N -aralkylpyridinium cations as solutes in water or acetonitrile: (C 6 H 5 )CH 2 ( + NC 5 H 5 ), (4-ClC 6 H 4 )CH 2 ( + NC 5 H 5 ), (3-ClC 6 H 4 )CH 2 ( + NC 5 H 5 ), 3-ClC 6 H 4 )CH 2 (2′-Me + NC 5 H 4 ), (4-NO 2 C 6 H 4 )CH 2 ( + NC 5 H 5 ), (2,5-Me 2 C 6 H 3 )CH 2 ( + NC 5 H 5 ), (2,5-Me 2 C 6 H 3 )CH 2 (2′-Me + NC 5 H 4 ), (2,4,6-Me 3 C 6 H 2 )CH 2 ( + NC 5 H 5 ), (2,3,5,6-Me 4 C 6 H)CH 2 ( + NC 5 H 5 ), (2,3,5,6-Me 4 C 6 H)CH 2 (2′-Me + NC 5 H 4 ), (2,3,4,5,6-Me 5 C 6 )CH 2 ( + NC 5 H 5 ) and (2,3,4,5,6-Me 5 C 6 )CH 2 (2′-Me + NC 5 H 4 ). The data are analysed in terms of the preferred conformations adopted by such cations in formations, where both aryl and pyridinium rings are twisted in the same direction with respect to the C ar -CH 2 -N ar reference plane. In contrast, tri-ortho-substituted diaryl cations adopt an asymmetric form in which the ortho-substituted aromatic ring lies almost perpendicular to the reference plane, and the mono-ortho-pyridinium ring forms an acute angle with the reference plane.

Thermodynamic and kinetic analyses of probable chemical reactions in the tribocontact zone and the effect of heavy pressure on evolution of adsorption processes

The paper presents thermodynamic and kinetic analyses of probable chemical reactions and adsorption processes depending on their energy, temperature, and pressure. It is shown that only lubricating adsorption films that appear on the rubbing surfaces due to mechanoactivated reactions can play a significant role in improving the tribological properties of a sliding contact. It is also demonstrated that heavy pressures in the zone of real contact between the asperities of rubbing surfaces enhance equilibrium adsorption of low-molecular-weight additives and of a number of high-molecular-weight additives to fluid lubricants.

Population of transition states of triboactivated chemical processes

The population of transition states of friction-induced chemical processes and similar thermo-induced reactions is analyzed. Friction is shown to be a unique natural phenomenon that involves the occurrence of highly inverse transition states of chemical interaction between contact material particles, as opposed to thermally populated transition states analogous in terms of the energy level of the reactions. It is found that in evaluating the population of transition states of mechano- and thermoactivated reactions, the specific chemical interactions do not matter and only the energies of the transition states of the thermo- and mechanoactivated processes are of importance.

Conformational investigation of diarylsulphides by Kerr effect and dipole moment methods

Abstract Molar Kerr constants and electric dipole moments are reported for (4-NO 2 C 6 H 4 ) 2 S, (4-MeOC 6 H 4 ) 2 S, (4-MeOC 6 H 4 ) (4′-NO 2 C 6 H 4 )S, (2-MeOC 6 H 4 ) (4′-NO 2 C 6 H 4 )S, 4(MeOC 6 H 4 ) (2′-NO 2 C 6 H 4 )S, (2-MeOC 6 H 4 ) (2′-NO 2 C 6 H 4 )S and (4-ClC 6 H 4 ) 2 SO as solutes in dioxane at 298 K. The data are analysed in terms of the preferred conformations adopted in solution. In most cases these data are consistent with the presence, in dioxane, of helical conformers, where both aromatic rings are twisted in the same direction with respect to the C Ar SC Ar molecular reference plane. The (4-ClC 6 H 4 ) 2 SO molecule adopts an orthrogonal conformation where both aryl rings are approximately perpendicular to the C Ar SC Ar molecular reference plane.

Mechanoactivation in friction and the laws of sliding and rolling friction

The concepts of the collision theory and the activated complex theory, widely known in chemical kinetics and adapted to the description of contact between asperities on rubbing surfaces, are used to derive the expressions of Amontons’ law for sliding friction and Coulomb’s law for rolling friction. A semiquantitative relation between the sliding and rolling friction coefficients is found. Based on the expressions, the energy of interaction between the asperities and the friction coefficient in systems with selective transfer is estimated.

Molecular Polarizability of Organic Compounds and Their Complexes: XLVII. Conformations of Some 2,4,6-Triarylpyridines, 2-Aryl-4-phenyl-6-tert-butylpyridines, and the Corresponding Pyridinium Cations in Solutions, as Determined from the Cotton-Mouton Effect

The conformations of some 2,4,6-triarylpyridines, 2-aryl-4-phenyl-6-tert-butylpyridines, and the corresponding pyridinium cations in dioxane and acetonitrile solutions were determined from the Cotton-Mouton effect. These systems are nonplanar; the angles by which the aryl substituents at positions 2 and 6 of the heteroring are turned relative to the heteroring plane are close to those observed in biphenyl and its p-substituted derivatives; these angles depend on substituents in the rings and, in the case of cations, at the pyridinium nitrogen atom.

Kinetics of mechanoactivation of tribochemical processes

Active collision theory and activated complex theory are used to derive the general kinetic equations of the mechanoactivation of tribochemical processes in systems with boundary and mixed sliding friction. The nature of the weak temperature dependence of the velocities of tribochemical reactions compared to the corresponding thermoactivated processes is discussed. Various specific cases of mechanoactivation kinetics are considered and some of them are illustrated using examples of reactions with the selective transfer and wear of rubbing solids.

Conformational investigation of 1,8-disubstituted naphthalenes as solutes by Kerr effect and dipole moment methods

Abstract Molar Kerr constants and electric dipole moments are reported for 1-methoxycarbonylnaphthalene, 1-bromo-5-methoxycarbonylnaphthalene, 1-bromo-5-nitronaphthalene, 1-amino-8-bromonaphthalene, 1-dimethylamino-8-methoxycarbonylnaphthalene and 1-dimethylamino-8-dimethylthiocarbamoylnaphthalene as solutes in dioxane at 298 K. The data are analyzed in terms of the preferred conformations in solution. These data are consistent with acoplanar orientations of 1- and 1,8-substituents relative to the naphthalene plane. The preferred conformers of the last two molecules are stabilized by a Me 2 N ⋯ C  O(S) through-space interaction.

Effect of pressure on chemical reactions in the zone of direct friction contact of systems with selective transfer

The paper deals with the effect of heavy pressure in the zone of real tribocontact on the rate of the reactions of complexing of copper chelates that provide the formation of a servovite film and implementation of selective transfer. It is shown that heavy pressures accelerate significantly the complexing reactions at the initial stages of servovite film formation during selective transfer. The procedure of search for potential complexing agents for implementing selective transfer can be simplified by using the developed method of mole volumes. This method allows the prediction of the efficiency of a complexing ligand at the initial stage of servovite film formation with account for heavy real pressures.

A Kerr effect study of conformations of 1,8-disubsituted naphtalenes as solutes

Molar Kerr constants and electric dipole moments are reported moments for 1,8-diacetylnaphthalene, 1,8-bits(dimethylcarbamoyl) naphthalene, 1-dimethylcarbamoylnaphthalene, 1-dimethylaminonaphthalene, 1-dimethylamino-5-bromonaphthalene, 1-dimethylamino-8-acetylnaphthalene and 1-dimethylamino-8-dimethylcarbamoylnaphthalene as solutes in dioxane at 298 K. The data are analyzed in terms of the prefered solution-state conformations.These data are consistent with the presence in dioxane of acoplanar orientations of substituents to the naphthalene plane. The first and second molecule have substituent orientations almost orthogonal to the naphthalene moiety and the carbonyl groups in anti positions. Preferred confoemers of the last two molecules are stabilized due to the Me2N⋯CO through-space interactions.