Study on thermal decomposition kinetics of N,N′-bis(5,5-dimethyl-2-phospha-2-thio-1,3-dioxan-2-yl)ethylenediamine in air

The thermal decomposition kinetics of the N,N′-bis(5,5-dimethyl-2-phospha-2-thio-1,3-dioxan-2-yl) ethylenediamine (DPTDEDA) in air were studied by TGDTG techniques. The kinetic parameters of the decomposition process for the title compound in the two main thermal decomposition steps were calculated through the Friedman and Flynn-Wall-Ozawsa (FWO) methods and the thermal decomposition mechanism of DPTDEDA was also studied with the Coats-Redfern and Achar methods. The results show that the activation energies for the two main thermal decomposition steps are 128.03 and 92.59 kJ·mol⁻¹ with the Friedman method, and 138.75 and 106.78 kJ·mol⁻¹ with the FWO method, respectively. Although there are two main thermal decomposition steps for DPTDEDA in air, the thermal decomposition mechanism of DPTDEDA in the two steps are the same, i.e. f(α) = 3/2(1 − α)^4/3[(1 − α)^−1/3 − 1]⁻¹. __________ Translated from Acta Chimica Sinica, 2008, 66(9) (in Chinese)     

DBC-偶氮肿-锇-溴酸钾催化光度法测定微量锇

酸性介质中Os(Ⅳ)对溴酸钾氧化DBC-偶氮肿的褪色反应有明显的催化作用,据此反应建立了微量娥的催化光度分析法,锇在1.0-20.0μg·L-1符合比耳定律.反应在水相中进行,灵敏度高,简便快速,用于贵金属精矿中娥的测定,结果满意.     

Theoretical study of self‐exchange electron‐transfer reactions for the M(H2O)\documentclass{article}\pagestyle{empty}\begin{document}$^{2+/3+}_{6}$\end{document} (M = V,Cr, Mn,and Fe) systems

Based on an activation model, a available scheme to calculate the rate of the electron‐transfer reaction between transition‐metal complexes in aqueous solution is presented. Ab initio technique is used to determine the electron‐transfer reactivity of the type M(H₂O)$^{2+/3+}_{6}$ of transition‐metal complexes at the UMP2/6‐311G level. The activation parameters and activation energies of the electron‐transfer systems are obtained via the activation model. An alternative determining method of the potential energy surface (curve) slope at the crossing point is given in which the inner‐sphere contribution of potential energy surface slope is expressed as the sum of two separate reactants. Theoretical self‐exchange rate constants for M(H₂O)$^{2+/3+}_{6}$ (M = V, Cr, Mn, and Fe) systems are obtained at 298 K and zero ionic strength. The calculated results of the activation energy, electronic transmission factor, and electron‐transfer rate are compared with the corresponding quasi‐experimental values as well as those obtained from other methods, and better agreements are found. The present results indicate that the scheme can adequately describe the self‐exchange reactions involved in this study. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 78: 32–41, 2000     

Hydrophobically modified polyelectrolytes III. Reactivity ratio determination of FX14/AA,LA/AA and SA/AA

The reactivity ratios of three hydrophobic monomers, FX14, LA and SA, to hydrophilic monomer, acrylic acid (AA), were determined. For the fluorocarbon containing hydrophobic monomer FX14, elemental analysis was adopted to obtain the relative content of FX14 to AA. For two hydrocarbon monomers, ¹³C NMR was used. FR, KT linear method and EVM nonlinear method were applied in calculating reactivity ratios. It is found that the reactivity of LA and SA is lower than that of AA, for solution polymerization in cyclohexane. Whereas FX14 is more reactive than AA in benzene. Finally, the distribution of small amounts of these hydrophobic monomers along the polymeric chain is discussed and a random sequence is confirmed     

An order-disorder transition in Sr2IrD5: Evidence for square pyramidal IrD5 units from powder neutron diffraction data

Neutron diffraction data have been collected on a powdered sample of Sr₂IrD₅ over a range of temperatures. The compound, which is cubic at room temperature, has been found to exhibit a gradual transformation to a tetragonal phase in the temperature range 200-140 K. As a result of the transition, deuterium atoms which randomly occupy sixfold positions in the cubic phase, become tetragonally ordered. A small fraction of the cubic phase remained untransformed at 4.2 K. Both the cubic and tetragonal structures are consistent with square pyramidal IrD₅ units with average Ir---D distances of 1.714 and 1.718 Å, respectively. Agreement factors, R₁, for the two structural analyses are 3.44 and 4.94%.     

Optical Stark spectroscopy of the 2(0)(6) Ã1A'-X̃1A' band of chloro-methylene, HCCl

The laser induced fluorescence spectra of the 2(0)(6)A?(1)A(')-X?(1)A(') band of a rotationally cold (<20 K) molecular beam sample of chloro-methylene, HCCl, has been recorded, field-free and in the presence of a static electric field. The field-free spectrum has been analyzed to produce an improved set of spectroscopic parameters for the A?(1)A(') (060) vibronic state. The magnitude of the a-component of the permanent electric dipole moment, μ(a), for the X?(1)A(') (000) vibronic state has been determined to be 0.501(1) D from the analysis of the observed electric field induced shifts. Comparisons with theoretical predictions and flouro-methylene, HCF, are presented.     

Improved delay-leaping simulation algorithm for biochemical reaction systems with delays

In biochemical reaction systems dominated by delays, the simulation speed of the stochastic simulation algorithm depends on the size of the wait queue. As a result, it is important to control the size of the wait queue to improve the efficiency of the simulation. An improved accelerated delay stochastic simulation algorithm for biochemical reaction systems with delays, termed the improved delay-leaping algorithm, is proposed in this paper. The update method for the wait queue is effective in reducing the size of the queue as well as shortening the storage and access time, thereby accelerating the simulation speed. Numerical simulation on two examples indicates that this method not only obtains a more significant efficiency compared with the existing methods, but also can be widely applied in biochemical reaction systems with delays.     

Hydrothermal ammoniated treatment of PAN-graphite felt for vanadium redox flow battery

A novel method of hydrothermal ammoniated treatment on the polyacrylonitrile (PAN)-based graphite felt for vanadium redox flow battery was developed. The graphite felt was treated in a Teflon-lined stainless steel autoclave for different time at 180 °C. The content of nitrogen in the PAN graphite felt changed from 3.803% to 5.367% by adjusting treatment time to 15 h in ammonia solution, while FT-IR results indicated that nitrogenous groups were introduced. The electrochemical properties of these graphite felts were characterized by cyclic voltammetry, electrochemical impedance spectroscopy, as well as cell charge and discharge tests. The energy efficiency of the treated graphite felt reached 85% at a current density of 20 mA/cm². The corresponding coulombic efficiency and voltage efficiency were 95.3% and 75.1%, respectively. The improvement of the electrochemical properties for the treated graphite felt might be attributed to the increase of polar nitrogenous groups of carbon fiber surface, which facilitated charge transfer between electrode and vanadium ions.