Catalysis by Ir(III), Rh(III) and Pd(II) metal ions in the oxidation of organic compounds with H2O2

Catalytic activities of three transition metals, as iridium (III) chloride, rhodium (III) chloride and palladium (II) chloride, were compared in the oxidation of six aromatic aldehydes (benzaldehyde, p‐chloro benzaldehyde, p‐nitro benzaldehyde, m‐nitro benzaldehyde, p‐methoxy benzaldehyde and cinnamaldehyde), two hydrocarbons (viz. (anthracene and phenanthrene)) and one aromatic and one cyclic alcohol (cyclohexanol and benzyl alcohol) by 50% H₂O₂. The presence of traces (substrate: catalyst ratio equal to 1:62500 to 1:1961) of the chlorides of iridium(III), rhodium(III) and palladium(II) catalyze these oxidations, resulting in good to excellent yields. It was observed that in most of the cases palladium(II) chloride is the most efficient catalyst. Conditions for the highest and most economical yields were obtained. Deviation from the optimum conditions decreases the yields. Oxidation in aromatic aldehydes is selective at the aldehydeic group only and other groups remain unaffected. This new, simple and economical method, which is environmentally safe, also requires less time. Reactive species of catalysts, existing in the reaction mixture are also discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

A simple and sensitive analytical method for the determination of antimony in environmental and biological samples.

The results of a study and application of leucocrystal violet for the determination of antimony in parts per million levels is described here. The proposed method is based on the reaction of antimony(III) with acidified potassium iodate to liberate iodine. The liberated iodine selectively oxidizes leucocrystal violet to crystal violet dye. The formed dye shows maximum absorbance at 590 nm. The color system obeys Beer's law in the concentration range from 0.4 - 3.6 microg antimony per 25 ml of final solution. The molar absorptivity and Sandell's sensitivity were found to be 7.32 x 10(5) l mol(-1) cm(-1) and 0.0016 microg cm(-2), respectively. All variables were studied in order to optimize the reaction. The proposed method is satisfactorily applicable for the analysis of antimony in various environmental and biological samples. The method is simple, highly sensitive, accurate and reliable.     

Differential oscillator strengths and dipole polarizabilities for transitions of the helium sequence

The dipole radial integral for an initial discrete 1s state and a final continuum state has been calculated under the screened hydrogenic model. In this model, single-electron hydrogenic wave functions are employed and the initial and the final states are treated by two different effective-charge parameters. Numerical values of differential oscillator strengths for transitions from 1s 21S to the continuum for the helium sequence ions are obtained. Also calculated are the dipole polarizabilities, which are found to be in excellent agreement with the results of other authors.     

The maximum momentum transfer in proton-hydrogen collisions

The upper limit of momentum transfer by a proton to K-shell electrons is calculated in a restricted three-body classical model. The model shows that the infinite upper limit used in practice, is generally good except for low energy protons passing through an extremely rarefied gas.     

Telluro- and seleno-bridged TiIV-MII (M = Ni,Pd, Pt) heterobimetallic complexes

Summary Heterobimetallic complexes of the types [Cp₂Ti(-EAr)₂-M(dppe)] (ClO₄)₂ [(1)–(4); M, E = Ni, Te (1); Ni, Se (2); Pt, Te (3); Pt, Se (4); Ar = Ph (a), C₆H₄-4-Me (b), C₆H₄-4-OMe (c), C₆H₄-4-OEt (d)] and [Cp₂Ti(-TeAr)₂-MCl ₂] [M = Pd (5), Pt (6)] were obtained by the reactions of Cp₂Ti(EAr)₂ with M(dppe)(ClO₄)₂ and M(PhCN)₂Cl₂, respectively. While (1), (5) and (6) are stable in the solid state as well as in solution, (2)–(4) undergo dissociation to M(dppe)(EAr)₂ and Cp₂Ti(ClO₄)₂ in solution, as shown by multinuclear (³¹P{¹H},¹⁹⁵Pt{¹H}, ¹²⁵Te{¹H}) n.m.r. studies. The reaction of Cp₂Ti(SeAr)₂ with M(PhCN)₂Cl₂, however, leads to the formation of Cp₂TiCl₂ and a polymeric material [M(SeAr)₂] _n .     

Carbon nanohorns grown from ruthenium nanoparticles

A nanoscale ruthenium/gold bimetallic cluster of clusters has been used as a molecular precursor to produce pure ruthenium nanoparticles (seeds) as catalysts for the growth of carbon nanohorns (CNHs).     

Effect of Enzyme Modification of Corn Grits on their Properties as an Adsorbent in a Skarstrom Pressure Swing Cycle Dryer

Corn grits have been tested as a desiccant in a pressure swing adsorption (PSA) system to produce dry air. Two sizes of unmodified corn grits were tested in the PSA system: 2.16 and 0.978 mm in diameter, which dried moist air to dew points of –42°C and –69°C, respectively. A modification technology has been developed for the corn grits that gives an increase in the operational adsorptive capacity in a pressure swing adsorption system, so that they remove as much moisture from air as molecular sieves at the same conditions. After modification, 2.16 mm corn grits dry moist air to a –56°C dew point and the 0.978 mm corn grits dry air to a –80°C dew point. The modification process creates surface modifications on the corn grits apparently making more adsorption sites easily available. The modification procedure increases the specific surface area of the grits and possibly decreases the crystallinity, which would make more hydroxyl groups available for adsorption of water. Possible applications of using corn grits in the pressure swing adsorption system include industrial gas dryers, sorptive cooling air conditioners, and recycling equipment for industrial solvents.     

Spectroscopic correlation for OH stretching frequency shifts of water in crystal hydrates

The shift of the uncoupled OH stretching frequency of water (from its free state position) in crystal hydrates has been plotted against a parameter r⁰ obtained by subtracting the H-bond (OH...Y) length from the sum of the free state ionic radii of O and Y. From an analysis of this curve it is inferred that MO_w coordination in hydrates reduces the ionic size of water oxygen and its effect on the OH stretching frequency is opposite to that of H-bonding.     

Thermal decomposition studies on manganese(III) selenito complexes

The heats of immersion of the systems B₂O₃P₂O₅ and Na₂OB₂O₃P₂O₅ in pyridine have been measured by the use of a solution microcalorimeter. In the composition range R R = atomic ratio, B/P) the heat of immersion was relatively small and was almost independent of R. The heat increased markedly with boron content in R > 1. The increase of heat qualitatively parallels that of surface acidity. Introduction of the Na₂O component reduced both heat of immersion and acidity. MgO was immersed in a benzene solution of benzoic acid. The heat of immersion increased with an increase of surface basicity.