Palladium(II)-catalyzed oxidation of l-tryptophan by hexacyanoferrate(III) in perchloric acid medium: a kinetic and mechanistic approach

Abstract

The catalytic effect of palladium(II) on the oxidation of L-tryptophan by potassium hexacyanoferrate(III) has been investigated spectrophotometrically in aqueous perchloric acid medium. A first order dependence in [hexacyanoferrate(III)] and fractional-first order dependences in both [L-tryptophan] and [palladium(II)] were obtained. The reaction exhibits fractional-second order kinetics with respect to [H + ]. Reaction rate increased with increase in ionic strength and dielectric constant of the medium. The effect of temperature on the reaction rate has also been studied and activation parameters have been evaluated and discussed. Initial addition of the reaction product, hexacyanoferrate(II), does not affect the rate significantly. A plausible mechanistic scheme explaining all the observed kinetic results has been proposed. The final oxidation products are identified as indole-3-acetaldehyde, ammonium ion and carbon dioxide. The rate law associated with the reaction mechanism is derived.

A Study of the Kinetics and Mechanism of Oxidation of Fluorene by Alkaline Hexacyanoferrate(III)

“…Moreover, fluorene is considered as effective and pronounced precursor for synthesis of photochromic di and tetrahydroindolizines [11][12][13][14]. On the other hand, oxidation of organic compounds by hexacyanoferrate (III) has been a subject of much interest especially in alkaline media [15][16][17][18][19][20][21][22][23][24][25][26] because hexacyanoferrate (III) has a high stability, water solubility and moderate reduction potential [27]. A literature survey revealed no work has been reported about the kinetics of oxidation of fluorene by any oxidant.…”

Kinetics and Mechanism of Silver(I)-Catalyzed Oxidation of Tryptophan by Platinum(IV) in Perchlorate Solutions

“…They play a significant role in a number of metabolic reactions like biosynthesis of polypeptide, protein and nucleotides. Thus, the mechanism of analogous nonenzymatic chemical processes in the oxidation of amino acids is a potential area for intensive investigation [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] in order to understand some aspects of enzyme kinetics. Tryptophan (Trp) is an essential amino acid in the human diet.…”

A Comparative Kinetic Study of Silver(I)-Catalyzed Oxidations of Alanine and Valine by Platinum (IV) in Perchloric and Sulfuric Acids Solutions

“…Transition metal ions have been widely employed as homogenous catalysts for oxidation of organic and inorganic substrates [12][13][14][15][16][17][18][19][20][21][22] by different reaction pathways such as formation of complexes with the reactants, oxidation of a substrate, or the formation of free radicals [32]. Kinetic investigations on the oxidation of amino acids catalyzed by different metal ions are an important field of chemistry due to the role played by metals in biological systems.…”