Kinetics and mechanism of reaction of cis-α,β-dinitrostilbene with morpholine

Reaction of cis-content/u62676luv238w5u2/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">,content/u62676luv238w5u2/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-dinitrostilbene (substrate) with morpholine (reagent) in n-hexane leads to cis-content/u62676luv238w5u2/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-nitro-content/u62676luv238w5u2/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-morpholinostilbene (end product). The process is of first order with respect to the substrate and second order with respect to the reagent. Possible reaction mechanisms are analyzed, and it is established that the following are most probable on the basis of kinetic patterns and stereochemistry: development of a charge transfer complex having a hydrogen bond between the substrate nitro group and reagent amino group; reaction of the complex with a second reagent molecule and formation of a carbanion (this stage determines the overall reaction rate); and detachment of a nitrite ion from the nitrocarbanion and its protonation to form the end product.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. A. N. Nesmeyanov Institute of Heteroorganic Compound, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 78–83, January, 1992.     

Reaction paths of some open-shell reactive intermediates

The intermolecular interaction energy for reacting systems in singlet, triplet and doublet states was partitioned by the perturbation expansion method into the chemically meaningful five interaction terms: the Coulomb, exchange-repulsion, induction, dispersion, and charge-transfer energies. In the local ZDO approximation, these energy terms were evaluated for the dimerization of methylenes (^1,3CH₂), the additions of carbenes (^1,3CH₂ and^1,3CF₂) as well as amino radicals (²NH₂ and²NF₂) toward ethylene, and the hydrogen abstractions by methylenes (^1,3CH₂), nitrene (³NH), and hydroxyl radical (²OH) from methane. It has been found that the reaction path is much influenced by the spinmultiplicity, and that the charge-transfer and exchange-repulsion terms play a dominant role in determining the course of reactions.     

A molecular modelling study of the interaction of noradrenaline with theβ 2-adrenergic receptor

Summary A model of thecontent/mt45747106480760/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0"> ₂-adrenergic receptor binding site is built from the primary structure of the receptor, experimental evidence for key binding residues and analogy with a homologous protein of partially determined structure. It is suggested that residues Trp-109, Thr-110 and Asp-113 are involved in ligand binding. Noradrenaline is successfully docked into this model, and the results of an INDO molecular orbital calculation on the complex indicate that a charge transfer interaction between Trp-109 and noradrenaline is possible.     

高固含量聚合物乳液制备方法新进展

高固含量一直是聚合物乳液制备追求的目标 ,本文将高固含量 (>6 0 % )聚合物乳液的制备方法按机理分为控制乳胶粒直径分布 ,增大乳胶粒直径和使乳胶粒发生形变三类 ,详细评述了各种制备方法的研究进展 ,并对高固含量乳液制备的发展进行了展望。     

Formatation of pore structure in tape-cast alumina membranes – effects of binder content and firing temperature

Disc type ceramic aluminium oxide membrane has been prepared by tape casting technique. Thickness of this single layer membrane is in the range 200–300 μm. Porosity and pore size distribution have been determined by mercury porosimetry. Polymeric binder content of the green tape and the firing temperature are found to have strong influence on the average pore size, pore size distribution and overall porosity. Higher binder content promotes agglomeration of the ceramic particles, which on firing leads to wider pore size distribution and formation of closed pores. Pore coarsening is observed with increasing firing temperature.     

Electrochemical synthesis of π-indenyl-π-(3)-1,2-dicarbollyliron(III)

Co-electrolysis of potassium 1,2-dicarbadodecahydroundecaborate and indene in 0.1N sodium bromide solution in dimethylsulfoxide using iron electrodes afforded content/n251323828716v45/xxlarge960.gif" alt="pgr" align="BASELINE" BORDER="0">-indenyl-content/n251323828716v45/xxlarge960.gif" alt="pgr" align="BASELINE" BORDER="0">-(3)-1,2-dicarbollyliron(III).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 764–765, April, 1993.     

Phase separation of poly(γ-benzyl L-glutamate) to liquid crystal and isotropic solution in various helicogenic solvents

Solvent effects on the phase separation of poly(content/k1543646u1h68x72/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-benzyl L-glutamate) to liquid crystal and isotropic solution have been observed in various helicogenic solvents. The temperature-composition phase diagrams have been determined for each solution. The critical concentrations,content/k1543646u1h68x72/xxlarge957.gif" alt="ngr" align="BASELINE" BORDER="0"> ₂ ^* , at which the phase separation occours have been compared in various solvents. In dimethylformamide in which the polymer is molecularly dispersed, the observedcontent/k1543646u1h68x72/xxlarge957.gif" alt="ngr" align="BASELINE" BORDER="0"> ₂ ^* value has agreed with that calculated by Flory's theory. In some solvents in which the polymer aggregates in a head-to-tail mode such as chloroform, the observedcontent/k1543646u1h68x72/xxlarge957.gif" alt="ngr" align="BASELINE" BORDER="0"> ₂ ^* values have been considerably small. It is assumed that the polymer aggregates behave as longer particles than the original particles. In dioxane in which the polymer aggregates highly both in a head-to-tail and a side-by-side modes, thecontent/k1543646u1h68x72/xxlarge957.gif" alt="ngr" align="BASELINE" BORDER="0"> ₂ ^* value has been a little larger than that in chloroform. In this case the relationship between the aggregation and the liquid crystal formation is so complicated that further investigation is necessary. In aromatic solvents such asm-cresol that dissolves the polymer almost molecularly, thecontent/k1543646u1h68x72/xxlarge957.gif" alt="ngr" align="BASELINE" BORDER="0"> ₂ ^* is smaller than that in dimethylformamide. Therefore, the intermolecular interactions between the phenyl groups in the side groups of the polymer and those in solvent molecules must be considered.The author is grateful to Mr. K. Sano and Mr. M. Watanabe for their observation of the liquid crystal formation.     

Reactions of regioisomeric fluoroalkyl-containing β-aminovinyl ketones with hydrazines

Fluoroalkyl content/n757146t92365416/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-alkyl-content/n757146t92365416/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-aminovinyl ketones react with hydrazine hydrate to give the respective razoles and with phenylhydrazine they form a mixture of pyrazoles and 5 hydroxy-content/n757146t92365416/xxlarge948.gif" alt="delta" align="BASELINE" BORDER="0">²-pyrazolines. Alkyl(aryl) content/n757146t92365416/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-fluoroalkyl-content/n757146t92365416/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-aminovinylketones do not react with the hydrazines mentioned above. With 2,4-dinitrophenylhydrazine, both types of fluoroalkyl-containing content/n757146t92365416/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-aminovinyl ketones give only hydrazones of the corresponding methyl alkyl(aryl) ketones.     

Effect of Oxygen Redistribution on the Normal and Superconducting Properties of Yttrium High‐Temperature Superconductors

An anomaly is found in the vicinity of T_maxcontent/p017n3j24422t914/xxlarge8764.gif" alt="sim" align="MIDDLE" BORDER="0"> 560$ K on electric resistance versus temperature curves for yttrium highcontent/p017n3j24422t914/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">temperature superconductors of the 123 phase. Xcontent/p017n3j24422t914/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">ray phase analysis suggests a structural phase transition in the vicinity of T_max due to oxygen redistribution in the mobile sublattice of this compound. Investigation of samples with Y partially replaced by Ca has shown that the structural phase transition does not depend on carrier concentration in the conduction band.     

Comparison of the Hartree-Fock,Møller-Plesset,and Hartree-Fock-Slater method with respect to electrostatic properties of small molecules

Summary The results of various quantum chemical calculations, the Hartree-Fock (HF) method, the Møller-Plesset perturbation theory (MP2), and the Hartree-Fock-Slater (HFS) method are compared. Atomic charges, dipole moments, topological properties of the electron density distribution and polarizabilities, and first hyperpolarizabilities are calculated. Atomic charges obtained with the HFS method are found to be very close to those calculated with the MP2 method, from which we conclude that the HFS method describes to some extent electron correlation effects. Performing an MP2 calculation after an HF calculation improves the molecular dipole moments considerably, yielding values close to the experimental ones. HFS calculations are computationally less demanding than MP2 and yield comparable results for the electron density distributions, dipole moments and polarizabilities.