The effect of chlorides on alginate gelation in the presence of calcium sulfate

The preparation of the alginate-CaSO₄-KCl/NH₄Cl gel phases is described. Dispersion of calcium sulfate in solutions with a low chloride content is found to lead to the formation of homogeneous alginate gels. The dependences of mechanical and absorptive properties of the gels on the chloride concentration are studied, and a possibility of practical application of the compositions thus prepared is shown. The effect of the KCl and NH₄Cl additives on gelation is explained by attainment of the optimal rate of CaSO₄ dissolution, which favors uniform distribution of Ca²⁺ cations in the bulk of the arising gel structure.     

16-Demethoxymethyllycaconitine,a new norditerpenoid alkaloid from Delphinium cuneatum

A new norditerpenoid alkaloid has been isolated from the roots of Delphinium cuneatum. On the basis of ¹H, ¹³C NMR, IR, and mass spectra, the structure of the alkaloid was established as 1,6,14-trimethoxy-7,8-dihydroxy-18-(2-methyl)succinylanthranoyloxyaconane (16-demethoxymethyllycaconitine). The roots of Delphinium cuneatum also contain the known alkaloid methyllycaconitine and N,N"-di(methoxycarbonyl)-3,4-diaminotoluene.     

Nitration of 5-formyl-substituted 2-cyclopropylfurans and 2-methylfurans and the corresponding thiophenes

In the nitration of 5-formyl-substituted 2-cyclopropylfurans and the corresponding thiophenes, in addition to the formation of the corresponding 3-nitro derivative the replacement of the formyl group by a nitro group takes place. For a thiophene derivative the latter direction of the reaction is observed to a substantially smaller degree. Under nitration conditions, 5-formylsylvane is converted only into 5-nitrosylvane, while the corresponding formylmethylthiophene is nitrated exclusively in position 3. The difference observed in the behavior on nitration of the furans and thiophenes studied is explained by the different degrees of participation of the heteroatom in the delocalization of the charges in the heterocyclic ipso-ions formed as intermediates.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 455–460, April, 1980.     

Effect of 2,2,6,6-tetramethyl-1-piperidinyloxy nitroxide substituent on kinetic parameters of pseudoliving polymerization

The main kinetic and thermodynamic parameters of the pseudoliving radical polymerization of styrene mediated by 4-linoleamido-2,2,6,6-tetramethyl-1-piperidinyloxy have been studied. It has been shown that the introduction of the said substituent into nitroxide leads to a marked reduction in the rate constant of reinitiation that is compensated for by the simultaneous reduction in the rate constant of reversible termination. As a result, the rate of pseudoliving polymerization, the rate of molecular mass growth, and the polydispersity of the polymer appear to be practically the same for processes mediated by both unsubstituted and substituted nitroxides.     

Methane conversion with carbon dioxide on nickel aluminides

The catalytic activity of several samples based on nickel aluminides in methane conversion with carbon dioxide was studied. Nickel aluminides were prepared by the method of self-propagating high-temperature synthesis. The Ni₃Al system containing the nickel metal phase exhibited high activity at temperatures above 1073 K. The systems based on Ni₂Al₃ and NiAl only containing intermetallic compound phases were inactive.     

Dependence of the reactivity of allophanates on the conformation of the main chain

The CNDO/2 method was used to investigate the conformation and structure of alkylsubstituted allophanates. The possibility of the existence of isomers both with coplanar and with noncoplanar main chains NCNC was studied. It was shown that the formation of conformers with a cis-structure of the ester group is more probable. On the basis of an analysis of the dependence of the reactivity on the structure of the main chain, hypotheses were advanced on the role of the more stable conformers in various channels of polyaddition of isocyanates.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 3, pp. 360–363, May–June, 1986.     

Influence of cation structure on decomposition of diacyl peroxides activated by chloride salts of amines

A kinetic study has been made of the interaction of benzoyl peroxide with a number of chloride salts of amines. It is shown that a change of the cation in quaternary ammonium salts does not have any significant effect on the kinetic parameters of the reaction. By means of NMR spectroscopy it has been determined that the structure of the NR₄ ⁺ cation does not change during the course of the reaction. The role of the cation in the process of activation of a diacyl peroxide by chloride salts of amines has been investigated by means of MNDO calculations.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 4, pp. 324–328, July–August, 1992.     

Magnetic anisotropy of cyclopropane and epoxide rings

MO LCAO results are presented for the interatomic contribution to the anisotropy of the diamagnetic susceptibility; values of _d=–23.5 · 10^–6 and _d=–13.8 · 10^–6 cm³/mole are obtained for the cyclopropane and epoxide ring systems, respectively. The results are used to interpret PMR spectra in terms of the configuration and conformation of the and forms of caran-4-ol and two stereoisomers of caranone.