Pyrocatechol and its derivatives as antioxidants and prooxidants

The effect of pyrocatechol and its derivatives (4,5-dichloro- and 4,5-dibromo pyrocatechols, veratrol, 4,5-dichloro- and 4,5-dibromoveratrol) on the free-radical oxidation of propan-2-ol in aqueous solutions, initiated by γ-radiation. Pyrocatechol and dihalocatechols exhibit antioxidant properties, whereas dihaloveratrols exhibit prooxidant properties. Dibromoveratrol showed more expressed prooxidant properties.     

On the Interaction of Semiquinones with Iron(III) Ions

High Energy Chemistry -     

Structure and reactions of carbon-centered α-oxy(Oxo)Radicals

The results of theoretical and experimental studies related to α-oxy(oxo)radicals are analyzed and generalized. The electronic structure, the effect of a medium on the electronic and spatial structure and the mechanisms of oxidation, α-and β-fragmentation, and isomerization reactions of radicals from various classes of oxygen-containing compounds (alcohols, ethers, aldehydes, acetals, and bifunctional and polyfunctional compounds) are considered. The mechanism of these reactions is based on two-orbital three-electron interaction in the >·C-O-and-·C =0 moieties of the above radicals.     

Reaction of semiquinones with chloroaromatic compounds

Semiquinones were generated by γ-irradiation of the quinone-containing water-ethanol solutions. The possibility of the reaction of semiquinones with sodium 2,4-dichlorophenoxyacetate and pentachlorophenol was studied. It was found that semiquinones reacted with chloroaromatic compounds to form chloride ions and phenyl radicals active in the abstraction reaction. By means of mathematic modeling the rate constant of the reaction of trimethylbenzosemiquinone with 2,4-dichlorophenoxyacetate was calculated.     

On the reaction of superoxide ion with organochloric compounds

Superoxide ions were generated by the action of γ-radiation on water-alcohol solutions saturated with oxygen. The reaction of superoxide ions with sodium 2,4-dichlorophenoxyacetate and pentachlorophenol was studied. The reaction of O₂ ^?? with chloroaromatic compounds results in elimination of chloride ions and formation of phenyl radicals active in elimination of hydrogen atoms. The rate constant of the reaction between O₂ ^?? and 2,4-dichlorophenoxyacetate was calculated using the method of mathematical simulation.     

Amide-imidol tautomerism in aromatic polyamides

Conclusions The invariance of the characteristics of electronic distribution and the presence of limiting values of (N) with increasing chain length permits us to conclude that the macromolecule of the aromatic polyamide behaves like an oligomeric molecule of five to ten monomer units. Evidently this circumstance also, and not only the disruption of coplanarity of the individual units of the macromolecule, explains a number of experimental data leading to the conclusion of the presence of blocks of conjugation in polymers with a system of conjugated bonds [22].With such substantial energetic profitability of the amide forms as is obtained from quantum mechanical calculations, we might expect substantial concentration predominance of these forms in real systems, and, consequently, natural experimental difficulties in the detection of imidol forms. Moreover, the results obtained permit an explanation of the presence of paramagnetic centers in polyamidoacids and polyaminoamidoacids without enlisting the concept of the existence of isoamide and isoimide forms in them [23].Vladimir Scientific Research Institute of Synthetic Resins. Translated from Zhumal Strukturnoi Khimii, Vol. 12, No. 5, pp. 822–830, September–October, 1971.     

γ-Radiation-Initiated Formation of Phenol and Diphenyl Ether from Halobenzenes

The formation of phenol was observed in aqueous alkaline solutions of chlorobenzene. Diphenyl ether was formed in aqueous tert-butanol solutions of chlorobenzene and bromobenzene in the presence of phenoxide ions. An increase in the temperature of irradiation resulted in an increase in the yields of phenol and diphenyl ether. At a temperature higher than 150°C, chain reactions of phenol and diphenyl ether formation occurred. It is likely that the dissociation of halobenzene radical anions is the rate-limiting step of the processes.     

The genesis of energy bands formed by sublattice states in alkaline-earth metal oxides and sulfides

The self-consistent electron energy band spectra of crystals and charged sublattices of alkaline-earth metal oxides and sulfides are calculated in the framework of the density functional theory within the pseudopotential approximation in the basis set of localized orbitals. The charge states of sublattices (such as neutral sublattices, empty metal sublattices, and doubly charged anion sublattices) are analyzed with due regard for the electrical neutrality of the crystal. It is demonstrated that the valence bands of the studied crystals are very similar to the valence bands of the doubly charged anion sublattices. The distributions of the valence electron densities of the crystals are virtually identical to those of the anion sublattices. The lower conduction bands of the crystals and doubly charged anion sublattices also almost coincide with each other for MgO and MgS but differ substantially for CaO and CaS. This is associated with the difference between the contributions from the anions and cations to the conduction band of the crystals. It is found that these contributions depend on the relative energy positions of p and d unoccupied states.