Amberlite IR-120：一种可重复利用的微波辅助条件下胺类化合物与甲酸N-甲酰化反应的催化剂

 A rapid and practical green route for the N-formylation of amines with formic acid using Amberlite IR-120 as a catalyst is described. This method provides an efficient and much improved modification over the reported methods in terms of yield, reaction time, and work-up procedure. A wide variety of substituents is tolerated, which is not the case for existing procedures.     

Voltammetric and spectroscopic investigations of 4-nitrophenylferrocene interacting with DNA

Cyclic voltammetry (CV) coupled with UV–vis and fluorescence spectroscopy were used to probe the interaction of potential anticancer drug, 4-nitrophenylferrocene (NFC) with DNA. The electrostatic interaction of the positively charged NFC with the anionic phosphate of DNA was evidenced by the findings like negative formal potential shift in CV, ionic strength effect, smaller bathochromic shift in UV–vis spectroscopy, incomplete quenching in the emission spectra and decrease in viscosity. The diffusion coefficients of the free and DNA bound forms of the drug were evaluated from Randles–Sevcik equation. The binding parameters like binding constant, ratio of binding constants (K_red/K_ox), binding site size and binding free energy were determined from voltammetric data. The binding constant was also determined from UV–vis and fluorescence spectroscopy with a value quite close to that obtained from CV.     

Electrochemical Investigation of Na‐Salt of 2‐Methyl‐3‐(4‐nitrophenyl)acrylate on Glassy Carbon Electrode

The electrochemical behavior of Na‐salt of 2‐methyl‐3‐(4‐nitrophenyl)acrylate (NPA) and its reduction product was studied by cyclic (CV), differential pulse(DPV) and square wave voltammetry (SWV) using a glassy carbon electrode (GCE). The results revealed that NPA is irreversibly reduced leading to the formation of a reduction product (P_NPA). For pH<9.0 the peak potential was linearly dependent on pH. For pH>9.0 the peak potential was pH‐independent and the value of pK_b≈9.0 was determined. The adsorbed P_NPA exhibited reversible redox reaction. The reduction of P_NPA was pH dependent. To ensure that the electrochemical behavior of NPA is due to the reducible moiety, NO₂, closely related compounds to NPA were also studied, and a redox mechanism was proposed for NPA.     

Kinetics of thermal decomposition of metal acetates

The acetates of magnesium, nickel, copper, manganese, sodium and barium were subjected to thermal decomposition by means of thermogravimetric techniques (TG) under a constant flow of nitrogen. The decompositions occurred in steps and the kinetics of every set of reactions was determined by the Coats and Redfern method. These results were analysed to establish the decomposition kinetics and hence to calculate activation energies. The activation energies were also determined by applying the Horowitz-Hugh method, which yielded similar results.

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Zusammenfassung Mittels TG in konstantem Stickstoffstrom wurde die thermische Zersetzung von Magnesium-, Nickel-, Kupfer-, Mangan-, Natrium- und Bariumazetat untersucht. Es erfolgte eine schrittweise Zersetzung, die Kinetik für jede der Reaktionen wurde mit Hilfe der Methode von Coats und Redfern bestimmt. Diese Ergebnisse wurden genutzt, um die Kinetik der Zersetzung und anschlie\end die Aktivierungsenergien festzustellen. Ähnliche Werte für die Aktivierungsenergien erhielt man auch mit Hilfe der Methode von Horowitz Hugh.

     

Thermodynamics of adsorption of acetone on active carbon supported metal adsorbents

Adsorption of acetone on active carbon and active carbon supported metals (Ni, Cu, Zn and Cd) have been studied as a function of temperature. Thermodynamic parameters such as G ⁰, H ⁰, and S ⁰ are calculated from virial and Langmuir isotherm expressions. It is observed that active carbon supported metals have more adsorption affinity for acetone as compared to active carbon. Results show that the increase in adsorption affinity for active carbon supported metals is not due to configurational factors affecting the entropy of adsorption, but because of enhanced enthalpy of adsorption. XRD spectra show that active carbon supported metals adsorbents are amorphous and metal residues are present on the surface of active carbon in its reduced form. From adsorption data, isosteric heats and molar entropies of adsorption were calculated as a function of coverages and temperature. The values of isosteric heats of adsorption were found to be higher for active carbon supported metals, which may be due to the chemisorption of adsorbate molecules with metal sites present on the surface of active carbon. The extent of coordination of adsorbate molecules with metal sites is discussed on the basis of the acidic character of metal.     

Effect of pH on the adsorption of Ce3+, Sm3+, Eu3+ and Gd3+ ions on activated charcoal

The adsorption of metal ions such as Ce³⁺, Sm³⁺, Eu³⁺ and Gd³⁺ ions on activated charcoal has been studied as a function of pH. The adsorption mechanism of these ions is discussed in terms of hydrolyzed species formed in aqueous solution at different pH.     

Surface characterization and thermodynamics of adsorption of Sr2+, Ce3+, Sm3+, Gd3+, Th4+, UO 2 2+ on activated charcoal from aqueous solution

Surface parameters of the activated charcoal were measured using precise instrumental techniques for dehydration, carbon content, trace metals impurities, anions, bulk, tap and true densities, surface area, pore volume, porosity and average particle diameter. The adsorption of Sr²⁺, Ce³⁺, Sm³⁺, Gd³⁺, Th⁴⁺ and UO ₂ ²⁺ ions on activated charcoal from aqueous solution was studied as a function of temperature. Thermodynamic parameters such as HH ⁰ and S ⁰ were calculated from the slopes and intercepts of the linear variation of lnK ₁ vs. 1/T, whereK ₃ is obtained from Langmuir equation. The results show endothermic heats of adsorption, but negative free energy values indicate that the adsorption process of metal ions on activated charcoal is favored at high temperature. The value of isosteric heat of adsorption, calculated from the Clausius-Clapeyron equation, shows that the surface of the activated charcoal is heterogeneous with respect to activity. A wavelength dispersive x-ray fluorescence spectrometer was used for measuring the concentration of metal ions.     

A study of metals supported on active carbon with a temperature programmed reduction (TPR) technique

The influence of active carbon as support on the reducibility of supported metals (Ni, Cu, Cd, Zn) has been studied by means of a temperature programmed reduction (TPR) technique. The TPR profiles indicate that active carbon behaves as a dispersion agent and the supported metal is dispersed in a disordered phase rather than as a stoichiometric compound. The hydrogen consumed in the reduction indicates that the metal residues are present in monovalent and divalent forms. High-temperature reduction peaks were also observed and are explained on the basis of metal-surface interactions and the porosity of the active carbon. Nitrogen adsorption reveals that the active carbon porosity decreases due to progressive closure of the pores when metals are supported on the surface of active carbon.     

Determination of lanthanides in uranium solutions by X-ray fluorescence spectrometry

An XRF-method for the determination of Sm, Gd, Dy, Er and Eu in uranium solution by use of simple polyethylene bottles has been established. Spectral interferences and matrix effects like absorption enhancement have been rectified using standards of similar composition in the absence of internal standard. Analytical application of the method used has been established on the basis of statistical evaluation.     

Forced convection over a semi-infinite flat plate

The problem of forced convection heat transfer over a semi-infinite flat plate is treated by the method of series truncation, so as to yield results valid from leading edge to far downstream (0 < -R ₀< ∞). Results are presented for Prandtl number Pr = 0.1, 0.7, and 10. It is found that the effect of leading edge on heat transfer is smaller than on skin friction.