Reactivities of mixed organozinc and mixed organocopper reagents, 2. Selective n-alkyl transfer in tri-n-butylphosphine-catalyzed acylation of n-alkyl phenylzincs; an atom economic synthesis of n-alkyl aryl ketones

Tri-n-butylphosphine-catalyzed acylation of mixed n-alkyl phenylzincs with aromatic acyl halides in THF is efficient in selective transfer of n-alkyl groups to produce n-alkyl aryl ketones in good yields. This route provides an atom economic organocatalyzed alternative to transition metal-catalyzed acylation of di-n-alkylzincs.     

Voltammetric and spectroscopic studies on the interaction of anti-cancer herbal drug rutin with an anti-tuberculosis agent rifampicin

In this paper, the interaction of rutin (Rt) with rifampicin (RIF) has been investigated using voltammetric and spectroscopic techniques. With the addition of RIF into the Rt solution, both the reduction and oxidation currents of rutin decrease with few changes in the peak potentials and no new peaks appeared. The binding of Rt with RIF forms a kind of supramolecular complex Rt-RIF, which is electrochemically non-active. The experimental data showed that the formation of supramolecular complex is due to the electrostatic attraction of Rt with RIF. The binding reaction resulted in the decrease of the concentration of free Rt in the solution, and the decrease of the cathodic peak current of Rt. The stoichiometry of the Rt-RIF biocomplex was determinated to be 1: 1 by means of voltammetric data. The effect of pH on the binding reaction has been also studied. Based on the peak current values of Rt in the presence and absence of RIF, the binding constants of Rt-RIF at pHs 4, 7 and 9 were calculated as 0.72 × 10⁴ M⁻¹, 1.28 × 10⁴ M⁻¹ and 0.19 × 10⁴ M⁻¹, respectively. The experimental results indicate that there is a strength interaction between Rt and RIF in neutral pH. This binding reaction was supported by UV-Vis. and IR spectroscopy techniques.     

Monodisperse porous polymer particles with polyionic ligands for ion exchange separation of proteins

A new “grafting to” strategy was proposed for the preparation of polymer based ion exchange supports carrying polymeric ligands in the form of weak or strong ion exchangers. Monodisperse porous poly(glycidyl methacrylate-co-ethylene dimethacrylate), poly(GMA-co-EDM) particles 5.9 μm in size were synthesized by “modified seeded polymerization”. Poly(2,3-dihydroxypropyl methacrylate-co-ethylene dimethacrylate), poly(DHPM-co-EDM) particles were then obtained by the acidic hydrolysis of poly(GMA-co-EDM) particles. The hydroxyl functionalized beads were treated with 3-(trimethoxysilyl)propyl methacrylate to have covalently linked methacrylate groups on the particle surface. The selected monomers carrying weak or strong ionizable groups (2-acrylamido-2-methyl-1-propane sulfonic acid, AMPS; 2-dimethylaminoethylmethacrylate, DMAEM and N-[3-(dimethylamino)propyl] methacrylamide, DMAPM) were subsequently grafted onto the particles via immobilized methacrylate groups. The final polymer based materials with polyionic ligands were tried as chromatographic packing in the separation of proteins by ion exchange chromatography. The proteins were successfully separated both in the anion and cation exchange mode with higher column yields with respect to the previously proposed materials. The plate heights obtained for poly(AMPS) and poly(DMAEM) grafted poly(DHPM-co-EDM) particles by using proteins as the analytes were 80 and 200 μm, respectively. Additionally, the plate height exhibited no significant increase with the increasing linear flow rate in the range of 1–20 cm/min. The most important property of the proposed strategy is to be applicable for the synthesis of any type of ion exchanger both in the strong and weak form.     

Competitive kinetic study of the amination of organomagnesium and ‐zinc reagents with acetone O‐sulfonyloxime

Kinetic studies are reported for the electrophilic amination of substituted phenylmagnesium bromides and CuCN‐catalyzed phenylzinc chlorides with acetone O‐(2,4,6‐trimethylphenylsulfonyl)oxime in tetrahydrofuran at reflux temperature and at room temperature respectively. Substituent effects were determined by competition experiments. Rate data are analyzed via Hammett relationships to support the proposed mechanisms for the substitution of these organometallics with an electrophilic amino transfer reagent. Copyright © 2005 John Wiley & Sons, Ltd.     

High-energy gamma-rays accompanying the spontaneous fission of252Cf

Theγ-ray spectrum of²⁵²Cf(sf) was measured in the Darmstadt-Heidelberg Crystal Ball spectrometer, with a double ionization chamber mounted inside to detect the fission fragments. The measurement was aimed at a better understanding of an unusual component found in the high-energy region between 3 and 8 MeV, with fragment mass splits near symmetry. This component was proved to be predominantly emitted by the heavier fragment, to reach its highest intensity at a fragment mass split of 132:120, and to have an almost isotropic angular distribution. Calculations with the statistical code CASCADE could reproduce the main features.     

Interaction between Janus Green B and bovine serum albumin:Electrochemistry and spectroscopy studies

In this study,voltammetric and spectroscopic investigation of the interaction between Janus Green B(JGB) and bovine serum albumin(BSA) was reported.The interaction was observed at Britton-Robinson buffer(pH 7.0).When JGB was added to solution containing BSA,the peak currents of BSA decrease with the increasing of JGB concentrations which is due to the interaction of JGB and BSA.The binding constant of JGB with BSA was obtained by voltammetric data.Also,this interaction was supported by means of UV-vis spectroscopic measurements.The UV-vis absorption spectra of JGB in the presence of BSA decrease with the increasing of BSA concentrations.     

Isotropic matrix elements of the collision integral for the Boltzmann equation

We have proposed an algorithm for constructing matrix elements of the collision integral for the nonlinear Boltzmann equation isotropic in velocities. These matrix elements have been used to start the recurrent procedure for calculating matrix elements of the velocity-nonisotropic collision integral described in our previous publication. In addition, isotropic matrix elements are of independent interest for calculating isotropic relaxation in a number of physical kinetics problems. It has been shown that the coefficients of expansion of isotropic matrix elements in Ω integrals are connected by the recurrent relations that make it possible to construct the procedure of their sequential determination.     

Kinetic role of tert-amines in the osmium tetroxide catalyzed trimethylamine N-oxide dihydroxylation of cyclohexene

Effect of some tert-amines on the catalytic osmium tetroxide dihydroxylation of cyclohexene in aqueous tert-butyl alcohol has been investigated All amines have been found to retard the catalysis greatly and beyond a definite concentration of amine, the rate reaches a minimal and remains constant. The oxidation of cyclohexene is inhibited by pyridine, 2.2′-bipyridyl and DABCO with an inverse first-order dependence whereas inhibition by triphenylamine NN-diethylaniline, picoline pyrazine hexamethylenetetraamine and TMEDA shows an inverse partial order dependence. The inolvement of dioxomonoglycolatoosmium(VI) esters and their monoamine adducts in the rate determining oxidation step was established by the linear plots of 1/Δk₂ vs. 1/[L] where Δk₂ is the decrease in the second-order rate constant in the presence of [L] concentration of tert-amine. The ligand-accelerated or ligand-decelerated catalysis of tert-amines in the catalytic osmium tetraoxide dihydroxylation of alkenes may vary depending on the secondary oxidant on the alkene and on the structure and concentration of the tert-amine. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 359–366, 1997