Effect of the Structure of the Acyl Group on the Kinetics of Exchange between O-Nucleophiles

We have studied the rate of 15 reactions of acyl transfer from O-acyl salts of 4-dimethylaminostyryl-4-pyridine N-oxide to 4-morpholinopyridine and 4-dimethylaminopyridine N-oxides in acetonitrile solutions. Analysis of the results based on the Shaik – Pross approach and the Marcus equation shows that if the structure of the acyl group is varied, then the reactivity is determined by such parameters as the resonance interaction in the transition state (B) or the internal barrier (G ₀) of the reaction.     

Photoconductivity of gallium arsenide irradiated with 5 MeV protons

Several levels which develop in GaAs before and after proton irradiation were derived from the photoconductivity spectra. It is assumed that the majority of the levels which are observed after irradiation are related to uncontrollable impurities or to impurities which are activated during irradiation. The GaAs Cu samples were used to show that it is possible to activate admixtures by proton irradiation. It was established that the absolute photoconductivity is reduced during irradiation by the development of recombination centers. The average activation energy of these centers was estimated at 0.06 eV. Lattice defects are the recombination centers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 34–40, February, 1972.     

Rate and Equilibrium of Acetyl Group Exchange between Pyridines and Pyridine N-Oxides

22 Acetyl group exchange reactions between N-acetoxypyridinium salts and 4-dimethylaminopyridine, 4-morpholinopyridine, and N-methylimidazole in acetonitrile at 298 K have been studied. The rate constants varied from 10⁵ to 10^–4 L/mol·s, and the equilibrium constants ranged from 10⁹ to 10^–9. The rates and equilibrium constants of these reactions did not comply with the Brönsted equation. The kinetics of the acetyl exchange reactions are well described by a correlation equation containing squared terms.     

A comparison of the method of separation of physical variables with the two-field method for modeling the fluid dynamics of casting

We use the example of the two-dimensional problem of siphon filling of a mold by molten metal to compare two methods of studying the flow of a viscous fluid: in vortex-function flow variables (ω, ψ) and in pressurevelocity variables (p, v). The superiority of the (ω, ψ)-method is demonstrated. Two figures. Translated fromTeoreticheskaya i Prikladnaya Mekhanika, No. 25, 1995, pp. 130–132.     

Reaction of Acetyl and Benzoyl Chlorides with Pyridines and Pyridine N-Oxides

The rate of formation of N- and O-acetyl and benzoyl salts of pyridines and pyridine N-oxides in acetonitrile and methylene chloride and equilibria therein were studied. The process occurs in one step following the SN2 mechanism with a small degree of bond rupture in the transition state.