Photochemical reactions of 7-aminocoumarins

The photochemical reactions of 4-methyl-7-diethylaminocoumarin with the dimethyl ester of acetylenedicarboxylic acid, diethyl ester of maleic acid, and N-phenylmaleimide in the presence of oxygen and acetophenone give products of the heterocyclization at C(₆) and C(₈) of coumarin fragment with participation of the diethylamino group. The stereochemical structure of the compounds synthesized was demonstrated using PMR spectroscopy. A mechanism was proposed for this reaction involving the formation of an -amino radical and its addition to the acetylene or olefin, accompanied by attack on the aromatic ring with subsequent aromatization.See [1] for Communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 30–36, January, 1989.     

Dynamic properties,scaling and related freezing criteria of two- and three-dimensional colloidal dispersions

The static and dynamic properties of 2- and 3-dimensional dispersions of strongly interacting colloidal spheres are examined. Quasi-2-dimensional dispersions of particles interacting by long range electrostatic and dipolar magnetic forces, respectively, are investigated using Brownian dynamics computer simulations with hydrodynamic interactions included. The dynamics of 3-dimensional bulk dispersions of charge-stabilized and neutral colloidal spheres is determined from a fully self-consistent mode-coupling scheme. For systems with long range repulsive interactions the dynamic correlation functions are shown to obey dynamic scaling in terms of a characteristic relaxation time related to the mean particle distance. Hydrodynamic interactions introduce a second characteristic length scale, and they lead to more restricted scaling behaviour with an enhancement of self-diffusion and, for 2-dimensional systems, to the divergence of the short-time collective diffusion coefficient. As a consequence of dynamic scaling, a dynamic criterion for the onset of colloidal freezing related to long-time self-diffusion is shown to be equivalent to a static freezing criterion related to the 2- and 3-dimensional static structure factors. Alternative freezing criteria are given in terms of the long-time and the mean collective diffusion coefficients.     

Aperiodic carbides formed by crystallization of amorphous Fe-C alloys

Hyperfine Interactions - The structures of new carbides formed by crystallization of amorphous Fe1−x C x alloys (0.29&;lt;0.32) have been investigated by diffraction and Mössbauer...     

Morphological Transition of Schooling in 19th-Century France

The transformation over time of level sets—the sets of states for which a given function takes a given value—has no reason to be regular, especially in social science, where the structure of these level sets of a given variable may be altered by a fluctuating demography or disrupted by unexpected events, and where the actors contribute to shaping their space through investment policies. The pioneering construction of graphic derivatives of set-valued maps renews the understanding of dynamic level sets in social science. The exemplary case of schooling in 19th-century France shows the set derivatives of level sets and illustrates how the Franco-Prussian War of 1870–1871 disturbed the directions taken in 1867. A comparison of the observed changes of level sets with those observed under rational theoretical policies leads to the conclusion that the actors behaved with the ambition of optimizing the overall schooling incidence while reducing the gap between boys and girls.     

Synthesis,spectral-luminescence,and acid-base properties of 3-halo-7-aminocoumarins

The reactions of substituted coumarins with a variety of halogenating agents, leading to the formation of the corresponding 3-chloro-, 3-bromo-, and 3-iodo-7-aminocoumarins, have been studied. It has also been shown, based on the results of studies of the spectral-luminescence and acid-base characteristics of these 3-halo-7-aminocoumarins, that their basicity increases as the electron-donating nature of the substituent in the 4-position increases, and is also greater, as expected, for 3-iodo- and 3-chloro derivatives than for 3-bromo derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1600–1609, December, 1990.     

Spectral-luminescence and acid-base properties of 4,7-diaminocoumarins

The absorption and luminescence spectra of a series of 4,7-diaminocoumarins have been investigated in ethanol and acetonitrile solution. The pk_a ^I and pk_a ^II values for several of the compounds have been measured. It has been found that the site of primary protonation is the nitrogen atom in the 7-position, and that the second protonation reaction occurs at the lactone oxygen atom. The effects of steric and electronic factors on the spectral-luminescence and acid-base characteristics of these compounds are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1610–1618, December, 1990.     

Acid-catalyzed dimerization and aralkylation in divinylaromatic compound-aromatic solvent systems

On heating styrene and bis(4-vinylphenyl) ether or a linear unsaturated aromatic oligomer with terminal vinyl groups in aromatic solvents, depending on the temperature and concentration of toluene-p-sulfonic acid, there are obtained predominantly dimers and linear oligomers, and/or products of the alkylation of the aromatic solvent by the unsaturated monomers, dimers, and oligomers.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2566–2574, November, 1990.