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

The kinetics of oxidations of two aliphatic α-amino acids (AA), namely, alanine and valine by platinum (IV) has been investigated spectrophotometrically in perchloric and sulfuric acids solutions in the presence of silver (I) catalyst at a constant ionic strength of 1.0 mol dm -3 and at 25°C. The reactions were very slow to be measured in the absence of the catalyst. The reactions in both acids showed a first order dependence on both [Pt IV ] and [Ag I ], and less than unit order dependences with respect to both [AA] and [H + ]. Increasing ionic strength was found to decrease the oxidation rates. Under comparable experimental conditions, the oxidation rates of alanine and valine in perchloric acid solutions were found to be about five times higher than those obtained in sulfuric acid solutions and the oxidation rates of alanine in both acids were found to be higher than those recorded with respect to valine. A plausible oxidations mechanism has been proposed and the rate law expression has been derived. Both spectral and kinetic evidences revealed formation of 1:1 intermediate complexes between AA and Ag I in both acids before the rate-controlling step. Then the formed complexes react with the oxidant (Pt IV ) by an inner-sphere mechanism to give rise to the oxidation products of the amino acids which were identified as the corresponding aldehyde, ammonium ion and carbon dioxide. The activation parameters of the second order rate constants were evaluated and discussed.

[1]  A. Fawzy,et al.  Copper(II) catalysis for oxidation of l-tryptophan by hexacyanoferrate(III) in alkaline medium: A kinetic and mechanistic approach , 2017 .

[2]  A. Fawzy,et al.  Kinetics and mechanistic approach to the chromic acid oxidation of l-tryptophan with a spectral detection of chromium(III) product , 2016 .

[3]  A. Fawzy,et al.  Silver(I) catalysis of oxidative deamination and decarboxylation of l-asparagine and l-histidine by platinum(IV) in perchloric acid solutions: A comparative kinetics study , 2016 .

[4]  A. Fawzy.  Palladium(II)-catalyzed oxidation of l-tryptophan by hexacyanoferrate(III) in perchloric acid medium: a kinetic and mechanistic approach , 2016, Journal of Chemical Sciences.

[5]  A. Fawzy,et al.  Transition metal-catalyzed oxidation of l-asparagine by platinum(IV) in acid medium: a kinetic and mechanistic study , 2015, Transition Metal Chemistry.

[6]  A. Fawzy,et al.  Kinetics and mechanism of uncatalyzed and silver(I)-catalyzed oxidation of l-histidine by hexachloroplatinate(IV) in acid medium , 2015, Transition Metal Chemistry.

[7]  A. Fawzy.  Kinetics and Mechanistic Approach to the Oxidative Behavior of Biological Anticancer Platinum(IV) Complex toward ‐Asparagine in Acid Medium and the Effect of Copper(II) Catalyst , 2015 .

[8]  A. Fawzy,et al.  Kinetics and Mechanism of Oxidation of l‐Histidine by Permanganate Ions in Sulfuric Acid Medium , 2014 .

[9]  A. Fawzy.  Influence of copper(II) catalyst on the oxidation of l-histidine by platinum(IV) in alkaline medium: a kinetic and mechanistic study , 2014, Transition Metal Chemistry.

[10]  A. Fawzy,et al.  Base-catalyzed oxidation of l-asparagine by alkaline permanganate and the effect of alkali metal ion catalysts: a kinetic and mechanistic approach , 2014, Reaction Kinetics, Mechanisms and Catalysis.

[11]  S. Chandraju,et al.  Oxidation of L-Valine by Manganese(III) in Pyrophosphate Medium: Kinetics and Mechanism , 2012 .

[12]  K. Sharanabasamma,et al.  Kinetics of Oxidation of L-Valine by a Copper(III) Periodate Complex in Alkaline Medium , 2012, Journal of Solution Chemistry.

[13]  M. Christian,et al.  New Cisplatin Analogues in Development , 1993, Drugs.

[14]  P. S. Sundaram,et al.  A kinetic and mechanistic study on the silver (I)-catalyzed oxidation of l-alanine by cerium (IV) in sulfuric acid medium , 2011 .

[15]  Ritu Singh,et al.  Oxidation of Amino acids by Manganese (III) in aqueous Sulphuric acid , 2011 .

[16]  S. T. Patil,et al.  Oxidative Deamination and Decarboxylation of L-Asparagine by the Aqueous Alkaline Diperiodatonickelate(IV) Complex , 2008 .

[17]  S. Upadhyay,et al.  Non-ionic micellar inhibition on the rate of oxidation of l-histidine by alkaline hexacyanoferrate(III) , 2008 .

[18]  M. Khalid.  OXIDATIVE KINETICS OF AMINO ACIDS BY PEROXYDISULFATE: EFFECT OF DIELECTRIC CONSTANT , 2008 .

[19]  K. R. Koch,et al.  195Pt NMR study of the speciation and preferential extraction of Pt(IV)-mixed halide complexes by diethylenetriamine-modified silica-based anion exchangers. , 2006, Inorganic chemistry.

[20]  M. Georgieva,et al.  Determination of platinum(IV) by UV spectrophotometry , 2003, Analytical and Bioanalytical Chemistry.

[21]  N. García,et al.  Oxidation of di- and tripeptides of tyrosine and valine mediated by singlet molecular oxygen, phosphate radicals and sulfate radicals. , 2001, Journal of photochemistry and photobiology. B, Biology.

[22]  T. Shi,et al.  Kinetics and mechanism for reduction of the anticancer prodrug trans,trans,trans-[PtCl2(OH)2(c-C6H11NH2)(NH3)] (JM335) by thiols. , 2000, Inorganic chemistry.

[23]  B. Pal,et al.  Kinetics and Mechanism of Hexachloroplatinate (IV) Reduction by Some Neutralized α-Hydroxy Acids in a Carbonate : Hydrogencarbonate Buffer Medium , 2000 .

[24]  K. Lemma,et al.  Kinetics and mechanism for reduction of oral anticancer platinum(IV) dicarboxylate compounds by L-ascorbate ions , 2000 .

[25]  P. Sharma,et al.  Kinetics and mechanism of oxidation of glycine, alanine, and threonine by fluoride coordinated bismuth(V) in aqueous HClO4–HF medium , 1994 .

[26]  R. Hassan.  Kinetics and mechanism of oxidation of DL-α-alanine by permanganate ion in acid perchlorate media , 1991 .

[27]  J. Garrido,et al.  Kinetics and mechanisms of the permanganate oxidation of l valine in neutral aqueous solutions , 1989 .

[28]  M. Nicol,et al.  Kinetics of the reduction of platinum(IV) by tin(II) and copper(I) in aqueous chloride solutions , 1977 .

[29]  W. Mason.  Platinum(ii)-catalyzed substitutions of platinum(iv) complexes , 1972 .

[30]  J. Beattie,et al.  Two-electron inner-sphere reduction of chloropentaammineplatinum(IV) ion by aquochromium(II) ion , 1971 .

[31]  J. Beattie,et al.  Reduction of some platinum(IV) comlexes with tris(bipyridine)chromium(II) ion , 1967 .

[32]  Ralph G. Pearson,et al.  Kinetics and mechanism , 1961 .

[33]  Fritz Feigl,et al.  Spot tests in organic analysis , 1956 .

[34]  J. W. COOK,et al.  A Text-Book of Practical Organic Chemistry , 1948, Nature.