A. Aziz Khan

Kinetics of the interaction of ninhydrin with a [Cr(histidine)(H2O)3]2+ complex

SummaryThe composition of the N-diketohydrindylidene histidinato chromium(III) complex formed by interaction of ninhydrin with the [Cr(histidine)(H2O)3]2+ complex has been determined using Jobs method of continuous variations. The reaction is slow and the kinetic studies were carried out under varying conditions of pH, temperature and [ninhydrin]. The observed pseudo-first order rate constant under these conditions follow the rate equation:

The studies on the composition and kinetics of the complex formed by the interaction of hexaaquochromium(III) with salicylic acid

{1 \mathord{\left/ {\vphantom {1 k}} \right. \kern-\nulldelimiterspace} k}_{obs} = {1 \mathord{\left/ {\vphantom {1 {\left\{ {K_t k_3 [N]} \right\} + {1 \mathord{\left/ {\vphantom {1 {k_3 }}} \right. \kern-\nulldelimiterspace} {k_3 }}}}} \right. \kern-\nulldelimiterspace} {\left\{ {K_t k_3 [N]} \right\} + {1 \mathord{\left/ {\vphantom {1 {k_3 }}} \right. \kern-\nulldelimiterspace} {k_3 }}}}

Physico-chemical studies on the interaction of transition metal ions with Schiff bases—II: Polarographic study of copper(II) complexes of o-vanillin-glycine, o-vanillin-aspartic acid and salicylaldehyde-aspartic acid

The reaction has the features of a template mechanism which proceeds through coordination of ninhydrin to the [Cr(histidine)]2+ complex. The reaction is expected to involve the combination of two ligands (ninhydrin and histidine) attached to the same CrIII (CLAM reaction). The CrIII ion provides a better opportunity for the reaction of ninhydrin and histidine by assembling their reactive groups together. On the basis of the observed data the probable mechanism has been proposed.

Amperometric studies on chromium (III) and iron (III) hydroxocyanotungstates (IV)

The composition of the complex formed by the interaction of hexaaquochromium(III) with acetate ions was determined by Jobs method of continuous variations and by conductivity measurements. It was found to be (1:2). Kinetic studies were carried out at 30, 35 and 40°C while the [H+] of the medium was varied from 0.1 × 10−4 M to 31.6 × 10−4 M. The variation of the pseudo-first order rate constant (kobs) with [H+] and the ligand concentration indicated a mechanism based on ion-pair formation and the following rate equation was derived on this basis: kobs=[kanKIKa[H+]+k′anK′IKa][acetate]T[H+]2[H+]Ka+[H+]K′I+KaK′I+[KIKa+[H+]+K′IK′aKa][acetate]T The reaction was found to be of the associative interchange (Ia) type for the reaction of Cr(H2O)63+ and dissociative interchange (Id) type for that of Cr(H2O)5OH2+ with acetate ions. The activation parameters, calculated using the Eyring equation are: ΔH∗ = 103 kJ mol−1; ΔS∗ = 31 JK−1mol−1 for the formation of Cr(H2O)5(OOCCH3)2+ and ΔH = 104 kJ mol−1; ΔS∗ = 41(±2)JK−1mol−1 for the formation of Cr(H2O)4OH(OOCCH3)+.

Studies on the kinetics and mechanism of the complex formation between hexa-aquachromium(III) and phthalic acid

Abstract The interaction of hexaaquochromium(III) with salicylic acid was studied in the pH range 2.5-4.2. The composition of the complex formed was one mole of salicylic acid to one mole of hexaaquochromium(III). The variation of pseudo first order rate constant with pH, ionic strength and ligand concentrations indicated a mechanism based on ion-pair formation. The rate equation derived on the basis of this mechanism is: k obs = k an K 1 K a [salicylic] T [H + +K a +K 1 K a [salicylic] T An associative interchange mechanism is suggested for the reaction. The activation parameters calculated by Eyring equation are ΔH ∗ = 74.48 (±0.33) kJ mol−1; ΔS ∗ = −60.49 (±1.11) JK−1 mol−1 for anation and ΔH = −9.00 (±0.43) kJ mol−1; ΔS = −13.60(±1.42) KJ−1 mol−1 for ion-pairing.

Kinetics and mechanism of decarboxylation of aspartic acid with ninhydrin

Abstract The interaction of copper(II) with salicylidene glycine schiff-base has been studied polarographically and the composition of the complex in methanol and aqueous media has been established. The polarographic reduction of the complex is found to be diffusion controlled but irreversible in nature.

Potentiometric estimation of tripotassium aquo-trihydroxotetracyanomolybdate (IV) and determination of standard potential

Abstract Copper(II) complexes with Schiff-bases derived from o -vanillin-glycine, o -vanillin-aspartic acid and salicylaldehyde-aspartic acid have been studied polarographically in aqueous and non-aqueous media at constant ionic strength. The reduction of copper in various concentrations of Schiff-base is diffusion controlled at sufficiently negative potential but not reversible. The kinetic parameters, stability constants and thermodynamic parameters are reported. The effect of pH has also been studied.

Kinetics and mechanism of ninhydrin reaction with copper(II) complexes of glycine and α‐alanine. Elucidation of the template mechanism

Die Zusammensetzung von in wässeriger Lösung gebildeten Ionenpaaren des Anions [W(CN)4(OH)4]4- mit Cr3+ bzw. Fe3+ wird amperometrisch ermittelt.