Ab initio investigations of structure and stability of the LiBeF3 molecule

Ab initio calculations of the potential energy surface of LiBeF₃ have been performed using the basis set of Roos and Siegbahn. The extremum and saddle points were made more precise with Huzinaga-Dunning basis sets in double-and triple-zeta contractions The “bidentate” structure (symmetry group C_2v) is found to have the lowest energy and is much more advantageous than the others, and the LiBeF₃ molecule turns out to be rigid with respect to migration of the cation around the anion. The calculated internuclear distances and the energy of complex formation are in agreement with experimental values within 0.03 Å and 2 kcal/mole. The results are compared with similar ab initio data for LiBeH₃ and LiNO₃.     

Catalytic asymmetric synthesis of methyl ester of N-acetyl-α-phenylalanine on chiral cobalt complexes

Conclusions The enantioselective hydrogenation of the methyl ester of N-acetyl--aminocinnamic acid on a catalytic chiral system based on cobalt was effected in an optical yield of 60%, which increases with increase in the phosphine/Co ratio in the catalyst and decreases with increase in the degree of conversion.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 720–723, March, 1984.     

Photoelectron spectroscopy of negative ions solvated in clusters

We have measured the photoelectron spectra of Cl^?, Br^? and I^? complexed with water molecule and of I^?·(CO₂) _n clusters wheren=1?7. The significance of these measurements to the understanding of solvation phenomena is discussed.     

Structure, 1H and 13C NMR spectra, and biological activity of the antibiotic INA-1278 related to irumamycin and produced by the experimental Streptomyces sp. strain No. 1278

The screening for novel antibiotic producers by selection methods revealed the Streptomyces sp. strain No. 1278 producing the antibiotic INA-1278, which exhibits antimicrobial and antifungal activities. This compound was isolated from the liquid culture by extraction with organic solvents and purified by chromatographic methods. The structure of this antibiotic was studied by mass spectrometry and ¹H and ¹³C NMR spectroscopy. An analysis of the results of the investigation indicate that the compound INA-1278 is structurally related to the antibiotic irumamycin, which has been studied earlier. However, the novel antibiotic may differ from irumamycin in the configurations of some asymmetric centers, which were not established at the present stage of our research.     

Regular trends in synthesis of sorption-active granular copolymers of methacrylic acid esters with polyvinylpyrrolidone

Granular copolymerization of compounds of 2-hydroxyethyl methacrylate and glycidyl methacrylate with polyvinylpyrrolidone in inert solvents was studied. The copolymers synthesized show promise as polymer systems for prolonged and controlled drug release.     

Products in the Reactions of Trialkyl Phosphites with α-Halogeno-acetophenones in Alcoholic Media

Abstract

α-Hydroxyphosphonates are formed, in addition to vinyl phosphates and dehalogenated ketones, in the reactions of trimethyl phosphite (in methanol) or triethyl phosphite (in ethanol) with variously substituted α-chloro, α-bromo, and α,α,-dichloro-acetophenones. Tri-isopropyl phosphite in propan-2-ol gives only the vinyl phosphate. Ketophosphonates are not detectable amongst the reaction products under the conditions used. Trends in product composition can be correlated with the leaving ability of halogen, substituent effects, structure of the phosphite, and reaction temperature. Reactant ratios may also influence the product composition. The reactions of trimethyl phosphite in methanol with 4-nitro-α-chloroacetophenone, or α,α-dichloroacetophenones yield the dehalogenated α-hydrogxyphosphonates in addition. In the case of the 4-nitro derivative, this product cannot be accounted for by reaction of the phosphite with dehalogenated ketone (4-nitroacetophenone). Dehalogenation of the first-formed α-hydroxyphosphonate was, however, shown to occur under reaction conditions and appears to require the removal of positive chlorine, followed by protonation. Reactions of the α,α-dichloroacetophenones were similar to those of the α-chloroacetophenones, giving the corresponding chlorovinyl phosphate, α,α-dichloro-α-hydroxyphosphonate, and monodehalogenated ketone(i.e. α-chloroacetophenone); the latter was not however detected as it reacted further with excess phosphite to give the expected products as described above. Possible mechanisms for the various reactions are discussed. The ¹H and ¹³C nmr spectra of the α-hydroxy-phosphonates show magnetic non-equivalence of the two alkoxy groups, attributed to restricted rotation about the P-C bond as a result of intramolecular hydrogen-bonding.     

Transverse vibrations of rectangular plates with edges elastically restrained against translation and rotation

The fundamental frequency coefficient for a rectangular plate with edges elastically restrained against both translation and rotation is calculated by using polynomial coordinate functions and the Rayleigh-Ritz method. The approach is simple and straightforward and allows the solution of a rather difficult elastodynamics problem. Complicating factors (orthotropic properties, in-plane forces, concentrated masses, etc.) can also be taken into account without formal difficulties.     

Analysis of mass transfer in dissipative nonideal systems: Experiments on dusty plasmas

Results of an experimental study of mass transfer are presented for extended systems of dust particles observed in capacitively coupled RF discharge plasmas. The Green-Kubo relation and the Langevin equation are validated as applied to dust grain dynamics in laboratory plasmas. A procedure is proposed for evaluating the temperature, friction coefficient, and characteristic oscillation frequency for dust grains. Measured characteristics of the dust subsystem (diffusion coefficient, pair correlation function, and friction coefficient) are compared with available theoretical and numerical results.