Mohamed M. Khalil

Equilibrium and hydrolysis of α-amino acid esters in mixed-ligand complexes withN-(acetamido)-iminodiacetatecopper(II)

SummaryThe formation equilibria of the binary and ternary complexes of CuII withN-(acetamido)-iminodiacetic acid (ADA) and amino acids or their esters were investigated potentiometrically. The chelation mode was ascertained by conductivity measurements. The kinetics of the base hydrolysis of amino acid esters in the presence of the copper(II)-ADA complex were studied. The rate and catalysis constants were estimated.

Metal complexes of salicylhydroxamic acid: equilibrium studies and synthesis

SummaryThe complex formation equilibria involved in the binary and ternary systems of MII-SHAM and MII-SHAM-L [M = Cu, Ni, Co, Zn, Cd, Mn, Hg, Ca or UO2; SHAM = salicylhydroxamic acid; L = the ligating agent, N-(2-acetamido)iminodiacetic acid (ADA), iminodiacetic acid (IDA) or nitrilotriacetic acid (NTA)] were investigated by the potentiometric technique at 25 °C and ionic strength 0.1 m NaNO3. The results indicate the formation of 1∶1 and 1∶2 (metal ion:ligand) SHAM complexes. The formation of mixed-ligand complexes followed a stepwise mechanism, whereby an ML complex was first formed, followed by the ligation of SHAM. The relative stability of the mixed-ligand complex was compared with that of the binary complex. The concentration distribution of the complexes possibly formed in solution was evaluated. Solid complexes of SHAM were prepared and characterized by microanalysis, conductivity, i.r., electronic and n.m.r. spectroscopies, and magnetic susceptibility measurements.

Kinetics of the oxidation of (N-(2-hydroxyethyl)-ethylene-diamine- N,N',N'-triacetato)cobalt(II) by N-bromosuccinimide

SummaryThe kinetics of the oxidation of [N-(2-hydroxyethyl)-ethylene-diamine-N,N′,N′-triacetato] cobalt(II), [CoII-(HEDTA)]−, by N-bromosuccinimide, NBS, have been studied in aqueous solutions and water-methanol solvent mixtures under various conditions. The reaction stoichiometry indicates that one mole of NBS reacts with one mole of [CoII(HEDTA)]−. In aqueous solutions the reaction obeys the following rate law:

Binary and ternary complexes of sulphamethoxazole

Rate = \left\{ {k_2 + k_3 /\left[ {H^ + } \right]} \right\}\left[ {Co^{11} \left( {HEDTA} \right)^ - } \right]\left[ {NBS} \right]

Hyamine 1622 - Selective PVC Membrane Electrodes Based on bis (Crown Ether)s

An inner sphere mechanism is proposed for pathway oxidation of both the protonated and deprotonated species of the complex, with the formation of an intermediate which slowly forms the final oxidation product, [CoIII(HEDTA)]. In water-methanol solvent mixtures the reaction rate decreased as the methanol content was increased. An appropriate mechanism, consistent with the kinetic results, is suggested.

Potentiometric Studies on Binary and Ternary Complexes of Di- and Trivalent Metal Ions Involving Some Hydroxamic Acids, Amino Acids, and Nucleic Acid Components

Abstract The Co, Ni, Cu, Pd and Hg complexes of 1-substituted-3-thiazole-2-ylthiourea have been prepared and characterized.

Mixed-Ligand Complex Formation Equilibria of Cobalt(II), Nickel(II), and Copper(II) with N,N-Bis(2-hydroxyethyl)glycine (Bicine) and Some Amino Acids

SummaryThe complex formation equilibria involved in the binary and ternary systemsM(II)-sulpha andM(II)-phen-sulpha were investigated by potentiometric titrations at 25°C and a ionic strength of 0.1N NaNO3 (M = Cu, Ni, Co, Zn;sulpha = sulphamethoxazole;phen = phenanthroline). The stability constants of the binary and ternary complexes follow the order ofIrving andWilliam. The formation of the ternary complex is discussed in terms of the binary species. The mode of chelation was ascertained by conductivity measurements.ZusammenfassungDie an den binären und ternären SystemenM(II)-sulpha undM(II)-phen-sulpha (M = Cu, Ni, Co, Zn;sulpha = Sulphamethoxazol;phen = Phenanthrolin) beteiligten Komplexbildungsgleichgewichte wurden bei 25°C und einer Ionenstärke von 0.1N NaNO3 mittels potentiometrischer Titration untersucht. Die Stabilitätskonstanten der binären und ternären Komplexe gehorchen der Reihenfolge vonIrving undWilliam. Die Bildung der ternären Komplexe wird auf der Basis der binären Spezies diskutiert. Die Art der Chelatbildung wurde durch Leitfähigkeitsmessungen ermittelt.

Equilibrium studies of binary and ternary complexes involving tricine and some selected α-amino acids

Abstract Coated wire ion-selective electrodes (CWISEs) for the Hyamine 1622 cation (Hy) based on dibenzo-18-crown-6 (DB18C6) and dibenzo-24-crown-8 (DB24C8) are developed. Both electrode systems exhibit stable near Nernstian response over the range 10−3–10−6 mole 1−1Hyamine 1622 cation with a slope in the range of 56–59 mv/decade of concentration. The working pH range is 3–9 and the response time varies from 30 to 50 s. The selectivity toward Hyamine 1622 cation is reasonably high relative to many common inorganic cations and organic cations not having surfactant properties. The electrode was suitable for determining the critical micelle concentration and as end-point detector in the potentiometric titration of the cationic surfactants.