Instrumental neutron activation analysis of peloids from main Cuban spas

Journal of Radioanalytical and Nuclear Chemistry - Peloids from some Cuban spas (San Diego, Elguea, Santa Lucía, Cajío and Colony) have been studied using Instrumental Neutron Activation...     

Adsorption of Cationic Surfactants on Silica Surface: 1. Adsorption Isotherms and Surface Charge

Adsorption isotherms of cationic surfactant, dodecylpyridinium chloride, on an Aerosil OX50 and isotherms of surface charge against the background of 0.001- and 0.1-M KCl solutions at pH 7 and 9 were measured and analyzed. Different forms of adsorption isotherms of surfactants at low and high electrolyte concentrations are explained from differences in the formation of the surface charge of Aerosil. Comparison of the isotherms of surfactant adsorption and surface charge allowed us to make conclusions about the surfactant orientation and structure of an adsorption layer, as well as to determine the fraction of surfactant molecules in the first and second adsorption layers.     

Structure and Electrosurface Properties of Porous Glasses with Different Compositions in KCl and NaCl Solutions

For porous glasses with and without small amounts of fluorine and phosphorus, structural (specific surface area, structure resistance coefficient, and mean pore radius) and electrosurface characteristics (adsorption of potential-determining ions, conductivity, counterion transport numbers, and electrokinetic potential) in sodium and potassium chloride solutions are compared. Results of measuring the equilibrium and transport characteristics of membranes are used to calculate the constants of surface reactions and adsorption potentials of ions within the framework of the 2-pK model of oxide surface charging. Within the framework of the homogeneous model, electrochemical characteristics of porous glasses, namely, concentrations of co- and counterions in a pore-confined liquid, Donnan potentials, convective component of the conductivity of a pore-confined solution, and mobility of counterions in the membranes, are calculated.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 3, 2005, pp. 342–351.Original Russian Text Copyright © 2005 by Ermakova, Medvedeva, Volkova, Sidorova, Antropova.     

Reaction of fullerene C60 with 2-azido-4,6-diphenylpyrimidine

The first representative of the pyrimidine-substituted [60]fullereno[1,2-b]aziridines was synthesized by the reaction of fullerene C₆₀ with 2-azido-4,6-diphenylpyrimidine. 2-(Azahomo[60]fullereno)-4,6-diphenylpyrimidine was found to be formed as a by-product. The electrochemical properties of the adducts were studied.     

Structure-property relationships for novel wholly aromatic polyamide-hydrazides containing various proportions of para-phenylene and meta-phenylene units: I. Synthesis and characterization

A series of novel wholly aromatic polyamide-hydrazides was synthesized by a low temperature solution polycondensation reaction of either 4-amino-3-hydroxybenzhydrazide or 3-amino-4-hydroxybenzhydrazide with an equimolar amount of either terephthaloyl chloride (TCl), isophthaloyl chloride (ICl), or mixtures of various molar ratios of TCl and ICl in anhydrous N,N-dimethylacetamide (DMAc) as a solvent. Polymer structures were identified by elemental analysis and infrared spectroscopy. All the polymers have the same structural formula except the way of linking phenylene units inside the polymer chain. The content of para- and meta-phenylene moieties was varied within this series so that the changes in the latter were 10 mol % from polymer to polymer, starting from an overall content of 0-100 mol %. The prepared polymers were characterized for their properties in order to acquire clear understanding of the influence exerted by controlled structural variations in these polymers upon some of important properties, such as solubility, intrinsic viscosity, moisture regain, mechanical properties and thermal as well as thermo-oxidative stability. The polymers were readily soluble in several organic polar solvents such as DMAc, N,N-dimethylformamide, dimethyl sulphoxide, N-methyl-2-pyrrolidone and hexamethyl phosphoramide and could be cast into flexible films. Their solubilities were found to increase remarkably with introduction of meta-phenylene moieties into the polymer chains. Their intrinsic viscosities ranged from 0.73 to 4.83 dl g⁻¹ in DMAc at 30 °C and increased with the increase of para-phenylene units content. Mechanical properties of the films produced from these polymers are improved markedly by substitution of para-phenylene units for meta-phenylene units. Thermogravimetric studies revealed that the completely para-oriented type of polymer has better thermal and thermo-oxidative stability relative to that of the other polymers. Moreover, the results reveal that the prepared polymers have a great affinity to water sorption. The hydrophilic character increases as a function of meta-oriented phenylene rings incorporated into the polymer chains.     

Conductimetric Studies of Charge Transfer Complexes of p‐Chloranil with Some Alicyclic Amines in Polar Media

The stoichiometry of charge‐transfer complexes which ionise in polar media has been studied by conductimetric titration technique in the systems morpholine‐p‐chloranil (CA), piperidine‐CA and pyrrolidine‐CA in three different polar solvents namely N,N‐dimethylformamide, acetonitrile and dimethylsulfoxide at different temperatures of 10, 15, 18, 20, 25 and 30 °C. The stoichiometric ratios of these complexes were found to vary from 1:1 to 1:4 (acceptor: donor) depending on the system, temperature and solvent used. The ασ_M‐values of these complexes have been reported. The effect of solvents, temperatures and types of electron donors on the σ_P‐values has been examined.     

Fluorine-Containing Heterocycles: VIII. Transformations of 2-Polyfluorobenzoylacrylates Having a Thiosemicarbazide Fragment

Depending on the conditions, 3-(4-R-thiosemicarbazido)-2-polyfluorobenzoylacrylates can be converted into the corresponding potassium salts, [1,3,4]thiadiazino[6,5,4-ij]quinolines, and pyrazole or 1,3,4-thiadiazole derivatives.     

A novel atom-transfer cyclisation catalysed by indium metal in halogenated solvents

Treatment of tethered alkyne-allyl halides 1a-d with indium metal in halogenated solvents affords carbocyclic vinyl halides (3a-d) via a novel atom-transfer reaction. The reactions are operationally facile and proceed smoothly at room temperature even with sub-stoichiometric quantities of the metal. Use of a halogenated solvent containing a different halide than that contained in the substrate affords a mixture of products arising from intramolecular halide transfer and abstraction of a halide atom from solvent.