Kinetics of the manganese(III)-oxalate reaction in acidic sulphate media

The kinetics of the reaction of manganese(III) with oxalic acid (OA) has been studied in H₂SO₄ solutions. Under the experimental conditions of 6 × 10^–3 <>₀ < 0.4=" mol=">^–3 and [H₂SO₄]₀ 0.2 mol dm^–3 the observed pseudo-first order rate constant k _obs follows the expression

Nitroxide‐mediated Living Radical Polymerization of Styrene with Fluorescent Initiator

A fluorescence method was used for determination of marked chain ends in polystyrene samples prepared by 4‐substituted TEMPO type nitroxide‐mediated living free radical polymerization of styrene. 2,2,6,6‐Tetramethyl‐1‐(1‐phenylethoxy)‐piperidin‐4‐yl‐4‐pyren‐1‐ylbutanoate (PYNOR) was prepared and used as an unimolecular initiator bearing pyrene as a fluorescence mark on mediating nitroxide fragment. The bulk polymerization of styrene at 120°C, in the presence of new unimolecular initiator, was a typical nitroxide mediated living radical polymerization. For comparison, two different molar ratios of initiator and monomer (1∶400 and 1∶1000 initiator ‐ monomer [I:M]) were used for polymerization. When I:M=1∶400, the obtained polydispersity was 1.12 and maximum molecular weight 27,000 g/mol was obtained at 62% conversion. For ratio 1∶1000, slightly higher polydispersity was obtained ?1.26 and the molecular weight was 53,000 g/mol at 70% conversion. The content of the polystyrene chains bearing mediating nitroxide fragment was determined by fluorescence spectroscopy. The intensity of pyrene fluorescence decreased as the molar mass, and the conversion increased as well. The extent of the incorporation of chromophore at propagating chain end or “livingness” of polymerization decreased despite the fact that the polydispersity did not change. The extent of side reaction leading to broadening of polydispersity is suppressed due to the high viscosity of the system at higher conversion. A low extent of “livingness” will have a very negative effect on possible preparation of block copolymers.     

The influence of the stretching mode on proton transfer in the H-bonded systems

A comparison between two models of proton transfer in the symmetric H-bond interacting in a thermal reservoir is made. It is shown that in a more general model (including both previous ones as special cases) a new qualitative feature in proton damping appears.     

Low-dimensional compounds containing cyano groups. III: a structural,spectral and thermal study of dicyanoargentates containing 4-methylpyridine

The complexes Cu^II(4-Mepy)₂Ag₂(CN)₄ (1) and Cu^II(4-Mepy)₃Ag_2–x Cu^I _x (CN)₄ (2) (4-Mepy = 4-methylpyridine, x = 0.07) were isolated from a reaction mixture containing 4-Mepy, K[Ag(CN)₂] and CuSO₄. I.r. spectra indicated the presence of both monodentate and bridging cyano groups in (1) and (2), confirmed by their known structures, both consisting of neutral zigzag chains. Two neighbouring chains in (2) are linked by argentophilic interactions between Ag atoms of bridging dicyanoargentate anions, whose positions are partly occupied by Cu^I ions to the extent of 7 at.%, with an unusually short Ag...Ag distance of 2.9264(5) Å, to form a ladder. Individual ladders are tied together as sheets by weaker argentophilic interactions between silver atoms of interdigitated monodentate dicyanoargentate anions of two different ladders. Thermal decomposition of (2) occurs in two separated stages. In the first stage, three 4-Mepy molecules are liberated from the formula unit and, in the second stage, redox decomposition of the cyano groups occurs. The thermal decomposition of (1) is more complicated as the release of two 4-Mepy molecules is overlapped by decomposition of one cyano group followed by further redox decomposition of the remaining cyano groups.     

The methylene blue‐D‐glucose‐O2 system. Oxidation of D‐glucose by methylene blue in the presence and the absence of oxygen

Quasi‐oscillations in [O₂] were observed during the methylene blue catalyzed oxidation of D‐glucose by O₂ in alkaline aqueous solutions. The kinetics of anaerobic oxidation of D‐glucose (GH) by methylene blue (MB⁺) was investigated in a closed system. The reaction was first order with respect to the concentration of methylene blue and the observed rate constant increased with GH concentration in a saturated mode. The oxidation proceeds via complex formation between GH and MB⁺ and the rate constant of the decay of the complex was determined. The oxidation process was also investigated under aerobic conditions and the reaction rates and reaction orders were determined by spectrophotometric measurements of the disappearance of MB⁺ and by amperometric determination of O₂ consumption. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 463–468, 1999     

Completeness properties of the generalized compact-open topology on partial functions with closed domains

The primary goal of the paper is to investigate the Baire property and weak α-favorability for the generalized compact-open topology τ_C on the space of continuous partial functions f :A→Y with a closed domain AX. Various sufficient and necessary conditions are given. It is shown, e.g., that is weakly α-favorable (and hence a Baire space), if X is a locally compact paracompact space and Y is a regular space having a completely metrizable dense subspace. As corollaries we get sufficient conditions for Baireness and weak α-favorability of the graph topology of Brandi and Ceppitelli introduced for applications in differential equations, as well as of the Fell hyperspace topology. The relationship between τ_C, the compact-open and Fell topologies, respectively is studied; moreover, a topological game is introduced and studied in order to facilitate the exposition of the above results.     

The Decay of Methylene Blue in Alkaline Solution

The decomposition of methylene blue in aqueous alkaline solution is described. The rate equation is of the form: , where k = 9.0 × 10^-4 mol^- [dm³s^-1 at 20°C and] = 0.5 mol dm^-3.     

Carbon dioxide evolution in a Belousov-Zhabotinsky type oscillating reaction with acetonedicarboxylic acid

Oscillations in the platinum redox potential during the reaction of bromate ions with acetonedicarboxylic acid catalyzed by Mn(II) ions were observed. The volume of gaseous carbon dioxide produced was measured. A nonoscillatory course was found both at the slow and rapid stirring rates for carbon dioxide evolution. The perturbation experiments suggest supersaturation during the Belousov-Zhabotinsky reaction with acetonedicarboxylic acid. Possible reasons for such observations are discussed.     

Vietoris topology on partial maps with compact domains

The space PK of partial maps with compact domains (identified with their graphs) forms a subspace of the hyperspace of nonempty compact subsets of a product space endowed with the Vietoris topology. Various completeness properties of PK, including ?ech-completeness, sieve completeness, strong Choquetness, and (hereditary) Baireness, are investigated. Some new results on the hyperspace K(X) of compact subsets of a Hausdorff X with the Vietoris topology are obtained; in particular, it is shown that there is a strongly Choquet X, with 1st category K(X).