Transfer reaction of the polystyrene radical with electron-acceptor molecules of tetrachlorophthalanhydride

The transfer constants (C_s) of the polystyrene radical with some derivatives of phthalic acid have been determined. Among the agents used, tetrachlorophthalanhydride (TCPA) differs distinctly from other compounds by its value of C_s 3·1 × 10^?3 for thermal and 3·4 × 10^?3 for initiated polymerization of styrene. The values of C_s for phthalanhydride, dimethyl phthalate, and tetrachlorodimethyl phthalate are lower by two decimal orders. The considerable decrease in the degree of polymerization of styrene prepared in the presence of TCPA is mainly attributed to the increased reactivity of chlorine atoms in TCPA induced by the acceptor effect of anhydride ring. Participation of a TCPA-styrene complex in transfer reaction has been assumed but not proved.     

Matrix-isolation FT-IR and DFT theoretical studies of the intramolecular hydrogen bonding in Mannich bases

FT-IR Ar-matrix isolated spectra were studied for dichloro- (Cl₂-MB) and tetrachloroderivatives (Cl₄-MB) of the ortho Mannich base. The spectra were analyzed based on the DFT calculated frequencies and intensities and compared with those recorded in CCl₄ solution in the region of the ν(OH) and ν(OD) vibrations. The matrix-isolated spectra are characterized by narrower ν(OH) and ν(OD) bands with much better resolved fine structure than in solution. The fine structure originates from the anharmonic coupling with the low frequency modes as well as from Fermi resonance. The ν(OD) band shapes can be reproduced exclusively by assuming the Fermi resonance with overtones and summation of the frequencies of modes into which the bridge atoms are involved. The frequency isotopic ratio (ISR) is for both compounds 1.33 while the half-width ratios are equal to 1.82 and 1.94, for Cl₂-MB and Cl₄-MB, respectively.     

The small momentum transfer k L o C→K S 0 C regeneration at high energies

Results of the first elastic K _S ^o regeneration experiment on carbon, using magnetic spark chamber spectrometer, are presented in the beam momentum interval 10p50 GeV/c. The d ifferentia cross section d/dt is reconstructed in the range 0·0025–t0·02 (GeV/c)² and its slopeB is found to be momentum independent with an average valueB=(65±11) (GeV/c)^–2. The results are in agreement with the calculations using the coherent production model.     

Dose-dependent effect of resveratrol on proliferation and apoptosis in endothelial and tumor cell cultures

Experimental data suggest that Resveratrol, a compound found in grapes and other fruits may influence cell proliferation and apoptosis. The aim of our experiments was to study the effect of Resveratrol on tumor cell cultures and an endothelial cell culture in order to examine the effect of various doses of this compound on active cell death and cell proliferation. Human tumor (HT-29, SW-620, HT-1080) and endothelial (HUV-EC-C) cells were treated with various doses of (0.1 to 100.0 microg/ml) Resveratrol in vitro. Cell number, apoptotic and mitotic index was measured 24, 48 and 72 h after treatment. Low doses (0.1-1.0 microg/ml) of Resveratrol enhance cell proliferation, higher doses (10.0-100.0 microg/ml) induce apoptosis and decrease mitotic activity, which is reflected in changes of cell number. Resveratrol influences dose dependently the proliferative and apoptotic activity of human tumor and endothelial cells. The possible role of formaldehyde in the mechanism of action of Resveratrol is discussed.     

A new synthesis of pyrazolo[1,5-d][1,2,4]triazines from pyrazolecarboxylic acid hydrazides and carbonyl compounds. I

Pyrazolo[1,5-d][1,2,4]triazines were synthesized from pyrazolecarboxylic acid hydrazides and carbonyl compounds. Pyrazolecarboxylic acid N-phenylhydrazide (1c) and formaldehyde gave not only the expected 4hn but 5 , respectively. The methyl substituted hydrazides with acetone afforded hydrazones, pyrazolotriazines or 13 depending on the position of the substituents. The reduction of both products yielded pyrazolecarboxylic acid hydrazides.     

Semiautomatic and automatic catalytic amperometric and catalytic constant-current potentiometric titrations of gold(III)

Semiautomatic and automatic amperometry and constant-current potentiometry were used to follow the course of catalytic titration of gold(III) with potassium iodide. The Ce(IV)-As(III) system in the presence of sulfuric acid was used as the indicator reaction. The possibilities of the application of two types of graphite electrodes were investigated. The effect of concentration of the indicator reaction components, and the presence of organic solvents and acids on the shape of the catalytic titration curves was studied. Amounts of 80–900 μg of gold(III) were determined with a relative standard deviation less than 1.1%. The results obtained are in good agreement with those of comparable methods.     

Pyrolysis Analysis and Kinetics of Crude Oils

This research presents the results of an experimental study on the determination of pyrolysis behaviour and kinetics of six crude oils by differential scanning calorimetry (DSC) and thermogravimetry (TG/DTG). Crude oil pyrolysis indicated two main temperature ranges where loss of mass was observed. The first region between ambient to 400°C was distillation. The second region between 400 and 600°C was visbreaking and thermal cracking. Arrhenius-type kinetic model is used to determine the kinetic parameters of crude oils studied. It was observed that as crude oils gets heavier (°API decreases) cracking activation energy increases. Activation energy of cracking also show a general trend with asphaltene content. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis of N-(4′-Benzo[15-crown-5])biphenylaminoglyoxime and Its Complexes with Some Transition Metals

N-(4-Benzo[15-crown-5])biphenylaminoglyoxime (H₂L) and sodium chloride salt of N-(4-benzo[15-crown-5])biphenylaminoglyoxime (H₂L · NaCl) have been prepared from 4-biphenylchloroglyoxime, 4-aminobenzo[15-crown-5], and sodium bicarbonate and sodium chloride. Nickel(II), cobalt(II), and copper(II) complexes with H₂L and H₂L · NaCl have a metal–ligand ratio of 1 : 2 and the ligand coordinates through the two N atoms, as do most of the vic-dioximes. Their IR spectra and elemental analyses are given, together with ¹H NMR spectra of the ligands.     

Coulometrische Titanbestimmung mit dreiwertigem Eisen

Zusammenfassung Es wurde eine coulometrische ferrimetrische Bestimmung von sehr kleinen Titanmengen nach der Reduktion mit zweiwertigem Chrom beschrieben. Bei 40 C und Anwesenheit von Chloriden ist es möglich, noch 5 g Ti in einer 20 ml-Probe mit einer Genauigkeit von etwa ±2% rel. zu bestimmen. Es wurde der Anteil der primÄren Oxydation von dreiwertigem Titan an der Anode wÄhrend der Titration verfolgt; bei den gelÄufigen Analysen bewegt sich die Generatorstrom-Ausbeute des dreiwertigen Eisens zwischen etwa 85 und 100%. Die Ursache der früher erwÄhnten [4] Störung durch Vanadium besteht in einer zu langsamen Gleichgewichtseinteilung zwischen zweiwertigem Vanadium, das bei der Reduktion von höherwertigen Vanadiumverbindungen durch zweiwertiges Chrom quantitativ gebildet wird, und vierwertigem Titan. Die Erhöhung der Arbeitstemperatur auf 60 C ermöglicht, Titan auch bei gro\em Vanadiumüberschu\ mit der gleichen Genauigkeit wie bei Abwesenheit von Vanadium zu bestimmen.

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Summary The coulometric ferrimetric determination of very small amounts of titanium after reduction with bivalent chromium is described. In chloride medium at 40 C it is possible to determine 5 g of titanium in a 20 ml sample with an accuracy of about 2% rel. The extent of the primary oxidation of trivalent titanium at the anode was studied in the course of the titrations. In actual analysis the generating efficiency of the trivalent iron is in the range of 85 to 100% The interference of vanadium observed previously [4] is due to a slow establishment of equilibrium between bivalent vanadium and tetravalent titanium. A quantitative reduction of trivalent vanadium by means of bivalent chromium was observed. When increasing the working temperatur to 60 C, it is possible to determine titanium even in great excess of vanadium with an accuracy corresponding to that obtainable in the absence of vanadium.

     

Toward designing molecular-electronics devices: A potential significance of highly mobile equilibrium interconversions

Possible applications of computational molecular-engineering approaches to the design of bistable conformational systems, to be potentially employed in molecular electronics, have been analyzed in isomeric–thermodynamic terms. Constructing such systems led to (conflicting) requirements, viz. an easy interconversion of the two structures (the isomerization equilibrium constant close to unity). At the same time there is a need for both isomers to be sufficiently stable and mutually different (enthalpy–entropy compensation can still ensure the equilibrium-constant requirement). Moreover, the equilibrium criteria have to be necessarily combined with considerations of kinetics. The design problems are illustrated on two model systems: Si₆H₆ isomeric species and deuterium- and hydrogen-bonded water dimers, HOD · OHD and DOH · OHD, respectively.