Mechanism of Oxidation of L-Cysteine by Hexachloroiridate(IV) — A Kinetic Study

Abstract

The kinetics of oxidation of L-Cysteine in aqueous HClO 4 medium were studied using a one-equivalent oxidant, hexachloroiridate(IV). The reaction exhibits second-order dependence with respect to hexachloroiridate(IV) and first-order in cysteine. The rate decreases with increase in hydrogen ion concentration indicating that the zwitterionic form of cysteine is more reactive. Cysteic acid is identified as the product of oxidation. A suitable mechanism involving the formation of [IrCl 6 ] 2) -sulphur bonded intermediate is proposed. The activation parameters of the reaction are computed using the linear least squares method and the values of E a and DS # are found to be 27.97±1.82 kJ mol )1 and )51.30±6.0 J K )1 mol )1 , respectively.

Synthesis and Characterization of Task‐Specific Ionic Liquids Based on Peroxydisulfate and Their Application in Oxidation Reactions

“…The selective oxidation of cysteine to cystine is a fundamentally important laboratory and commercial procedure and is conventionally carried out with stoichiometric amounts of metallic complex ions such as [Fe III (bpy) 2 (CN) 2 ] + ,19 [IrIVCl 6 ] 2– ,20 [Co III W 12 O 40 ] 5– ,21 [Fe III (CN) 6 ] 3– ,22 and [Co 2 (CN) 10 (O) 2 ] 5–[23] in volatile organic solvents. From both an economic and environmental point of view, developing a green process for converting cysteine to cystine on an industrial scale has been an important objective for chemists.…”

Orientation on Electron-Transfer Nature for Oxidation of Some Water-Soluble Carbohydrates: Kinetics and Mechanism of Hexacholroiridate (IV) Oxidation of Methyl Cellulose in Aqueous Perchlorate Solutions

“…A variety of reaction mechanisms was recognized in redox reactions involving hexachloroiridate (IV) as of oneequivalent nature [27][28][29][30][31]. Some of these reactions tend to proceed through formation of intermediate complexes of innersphere nature [14,15,21], outer-sphere type [32] or by both inner-and outer-sphere [33] mechanisms via free-radicals intervention. Other reactions are proceeding through outer-sphere mechanisms of non-free-radicals intervention [34][35][36][37][38][39][40][41][42], whereas the formation binuclear complexes [16,17] and ion-pairs [20] have been postulated for some other redox systems.…”

Kinetics and Mechanism of Catalyzed Oxidation of L-Cysteine by Salen Schiff Base Complexes of Co(III), Fe (III) and Cr(III)

“…Oxidation of L-cysteine have been the subject of several studies in recent years, using various kinetics techniques and various transition metal complexes (Jameson, Linert, Tschinkowitz, Gutmann,, 1988;Kottapalli, Adari, Vani, 2005;Laloo & Mahanti, 1990;Lay & Levina, 1996;Lemma Shi, Elding., 2000;Mehrotra Kapoor, Vajpai, 1984;Salomao et al, 2007;Sami Venkateshwari, Mariselvi, Mariselvi, Rajasekaran., 2010;Taube, 1970;Wang & Stanbury, 2008). As an extension of our previous studies Abdel-Halim,, Abu-Surrah, and Baker 2012;Abdel-Halim,Abu-Surrah, and Baker 2010;Abdel-Halim, Abu-Surrah, and Baker, 2006;Abdel-Halim, Saleh, Khreizat, 2018;Abdel-Halim, Saleh , Khreizat., 2015;H M Abdel-Halim, Salama, Al-Burtmani, 1998;Abdel-Halim, Abu-Surrah, Qaqish, 2006;Abu-Surrah, Abdel-Halim, Al-Qaisi, 2008;Abu-Surrah, Abdel-Halim, Feda'a, 2008) on both kinetics and catalytical application, and to widen our knowledge about the oxidation of biologically important amino acids we present this work.…”