Ion exchangers as catalysts. II. Catalytic decomposition of hydrogen peroxide with resin-ethylenediamine-copper(II) complex ions

Summary The slow decomposition of H₂O₂ in the presence of Dowex-50 W resin in the form of an ethylenediaminecopper(II) complex ion in water is accompanied by an induction period. The reaction is first order with respect to [H₂O₂] and the rate constant (perg of dry resin) was deduced. Autocatalytic behaviour was found for the H₂O₂ decomposition with 2% crosslinked divinylbenzene. The induction period disappeared and the reaction rate increased when the decomposition was carried out with a resin in the form of a peroxo-copper complex, which proves that the formation of an intermediate (active species) retards the reaction rate. The precursor of the active species, formed during the induction period, was not the amine-copper(II) complex ion but a product of the latter with H₂O₂. It proved impossible to carry out the decomposition in acid or buffer solutions, in which the resin is regenerated.     

Slow motion of a sphere moving normal to two infinite parallel plane walls in a micropolar fluid

In the present work, we consider the slow steady motion of a rigid sphere moving normal to two parallel plane walls in a micropolar fluid. Non-dimensional variables are introduced. A combined analytical-numerical technique based on the superposition principle and a numerical method, namely the collocation method, is used. The drag force and the wall correction factor are evaluated. Numerical results are obtained and represented graphically.     

A general formula for the drag on a sphere placed in a creeping unsteady micropolar fluid flow

In the present work, we investigate the creeping unsteady motion of an infinite micropolar fluid flow past a fixed sphere. The technique of Laplace transform is used. The drag formula is obtained in the physical domain analytically by using the complex inversion formula of the Laplace transform. The well known formula of Basset for the drag on a sphere placed in an unsteady viscous fluid flow and that of Ramkissoon and Majumdar for steady motion in the case of micropolar fluids are recovered as special cases. The obtained formula is employed to calculate the drag force for some micropolar fluid flows. Numerical results are obtained and represented graphically.     

Ion Exchangers as catalysts I. Catalytic decomposition of hydrogen peroxide in presence of Dowex 50 W resin in the form of ethylamine-copper(II) complex ion in aqueous medium

Summary Dowex 50 W resin in the form of an ethylamine-Cu¹¹ complex ion was used as potentially active catalyst for the decomposition of H₂O₂ in aqueous medium. The stoichiometry of the amine-Cu¹¹ complex on the resin, determined experimentally, was found to have the total [Cu²⁺]: [ethylamine]=14 concentration ratio. The kinetics of the decomposition was studied and the calculated rate constant (per g of dry resin) was found to decrease with increase the degree of resin crosslinking. The active species, formed as an intermediate at the beginning of the reaction, had an inhibiting effect on the reaction rate. The brown peroxo-copper complex formed as a result of H₂O₂ decomposition, was found to contain the catalytic active species. The order of the reaction increased with decreasing initial H₂O₂ concentration, a sign of a step-wise mechanism. A quantitative treatment of the decomposition of H₂O₂ was provided in terms of activation parameters.     

Catalytic decomposition of organic peroxides by 4,4′-diamino-trans-stilbene (DTS)/montmorillonite complex: II.p-nitro andp-methyl dibenzoyl peroxide

The kinetics of the induced decomposition ofp-NO₂- andp-CH₃-dibenzoyl peroxide in the presence of 4,4-diamino-trans-stilbene (DTS) were studied in ethanol under both homogenous and heterogeneous conditions. The heterogeneous reaction was carried out in the presence of the DTS/montmorillonite complex. The decomposition reaction was found to be second order and three-halves order for the peroxide concentration in homogeneous and heterogeneous systems, respectively. The reaction was first order for the amine concentration in the homogeneous system. The activation energies for the decomposition reaction were obtained as 54.7±2 and 59.5±3 kJ mol^–1 forp-NO₂- andp-CH₃-dibenzoyl peroxides, respectively, in the homogeneous systems and are higher than the corresponding values of 41±1.5 and 47.6±1 kJ mol^–1 for thep-NO₂ andp-CH₃ derivatives in heterogeneous media.     

The use of chloroalkyldichloroarsines in hybrid ligand synthesis. The preparation of but-3-enylbis(3-dimethylarsinopropyl)arsine and 3-dimethylarsinopropylbis(but-3-enyl)arsine,and their reaction with nickel(II) salts to form pentacoordinate complexes. Novel nickel(II)—olefin bonds

Routes have been developed to the hitherto unobtainable arsine-olefin ligands (CH₂CHCH₂CH₂)_nAs(CH₂CH₂CH₂AsMe₂)_3-n (n = 1, tasol, but-3-enylbis(3-dimethylarsinopropyl)arsine; n = 2, dasdol, 3-dimethylarsinopropylbis(but-3-enyl)arsine) by making use of the difference in reactivity between the ClC and AsCl bonds in the precursor Cl(CH₂)_mAsCl₂ (m = 2,3) molecules. Thus, the triarsine obtained by reaction of 2-chloroethyldichloroarsine with the Grignard reagent of 3-chloropropyldimethylarsine yields 2-chloroethylbis(3-dimethylarsinopropyl)arsine, from which tasol is obtainable by subsequent reaction with either the Grignard reagent of vinyl bromide or, preferably, with vinyllithium. Similarly, 3-chloropropyldichloroarsine reacts with the Grignard reagent of 4-chlorobut-1-ene to form 3-chloropropylbis(but-3-enyl)arsine which, on reaction with sodium dimethylarsenide yields dasdol. The tasol ligand reacts with nickel(II) salts to form [NiX(tasol)]⁺ (X = Cl, Br) and [NiI₂(tasol)], the former are trigonal bipyramidal and contain a nickel(II)—olefin bond, and the latter are square pyramidal containing a [NiI₂As₃] coordination sphere. In addition, tasol forms a number of polynuclear complexes with nickel(II). The dasdol ligand acts as a bidentate arsine to form only [NiX(dasdol)₂)]⁺ The formation of novel nickel(II)—olefin bonds in the [NiX(tasol)]⁺ cations is discussed.     

The catalytic effect of transition metal-ion ammine complexes on the decomposition of hydrogen peroxide in the presence of Dower-50W resin in aqueous medium

Summary The kinetics of the catalytic decomposition of hydrogen peroxide was studied in the presence of Dowex-50W resin in the form of some transition metal-ion ammine complexes in an aqueous medium. The transition metal-ions, Co²⁺, Ag⁺, Cd²⁺ and Zn²⁺ were chosen in this study and the rate constants (per gram of dry resin) were evaluated at various resin weights in the 25–40°C range. A coloured compound (peroxo-metal complex), which formed at the beginning of the reaction in each case, was found to contain the catalytic active species. Probable mechanisms for the reactions are proposed. The activation energy and the change in the entropy of activation increased in the following sequence: [Ag(NH₃]₂]⁺< [Cd(NH₃)₆]²⁺<[Co(NH₃)₆]²⁺<[Zn(NH₃)₆]²⁺, which is also the probability sequence for the formation of the activated complex.     

Exact solution for the unsteady flow of a semi-infinite micropolar fluid

The unsteady motion of an incompressible micropolar fluid filling a half-space bounded by a horizontal infinite plate that started to move suddenly is considered. Laplace transform techniques are used. The solution in the Laplace transform domain is obtained by using a direct approach. The inverse Laplace transforms are obtained in an exact manner using the complex inversion formula of the transform together with contour integration techniques. The solution in the case of classical viscous fluids is recovered as a special case of this work when the micropolarity coecient is assumed to be zero. Numerical computations are carried out and represented graphically.