Kinetics and Mechanism of the Reactions of Bis(biguanide)copper(II) Ion with Different Amino Acids in Aqueous Media
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Asim K. Das
Abstract
The kinetics of the reaction of [Cu(bigH)2]2+ (bigH = biguanide) with an excess of different amino acids (LH) like ß-alanine, L-phenylalanine and L-valine in aqueous solution in the 7.60-9.00 pH range at different temperatures (30-40°C) have been studied by stopped-flow spectrophotometry and compared with those of different ligands reacting with the title copper(II) complex. The ligand replacement process has been suggested to pass through an intermediate formation of the ternary complex, [Cu(bigH)L]+ as the rate determining step, followed by the rapid transformation into the binary complex, [CuL2]. The overall ligand replacement process follows a two-term rate law, kobs = k0 + k1Ka[L]T/([H+] + Ka, where [L]T gives the total concentration of the entering ligand, i.e. amino acid, and Κa gives the deprotonation constant of the amino acid (LH). Thus the process experiences both the ligand independent path (i.e. k0) and ligand dependent path (i.e. k0). The solvent assisted k0 path leads to a copper(II) mono-biguanide complex followed by the rapid nucleophilic substitution; the k1 path is in agreement with an associative mechanism. The k0 path is independent of the structure and basicity of the entering amino acids while the k0 path is dependent on the basicity and steric crowding of the entering amino acid. The reactivity order is: glycine > α-alanine > ß-alanine > L-valine > L-phenylalanine. The activation parameters have been evaluated. An iso-kinetic trend for different amino acids and other nucleophiles reacting with the title copper(II) complex has been found to prevail.
© 2014 by Walter de Gruyter Berlin/Boston
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- Kinetics and Mechanism of the Reactions of Bis(biguanide)copper(II) Ion with Different Amino Acids in Aqueous Media
- Keywords: Kinetics, copper(II), biguanide, amino acids, associative mechanism
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Artikel in diesem Heft
- Hypochlorite Oxidation of a Chromium(III) Schiff Base Complex
- Theoretical Estimates of Association Constants for Contact Triple-Ion Formation
- Inner Sphere Reduction of Tris(pyridine-2- carboxylato)manganese(III) by Hydroxylammonium Ion in Sodium Picolinate-Picolinic Acid Buffer Media
- The Complex Aqueous Chemistry of RUC12(TPPTS)3 and its Reaction with Dihydrogen
- Substitution Reactions of Platinum(II) Dipicolinate Complex with Some Mono- and Bidentate Ligands - Rates and Mechanism
- Kinetics and Mechanism of Oxidation of Azide Ion by 12-Tungstocobaltate(III), [CoW12O40]5-, Ion
- Osmium(VIII) Catalysed Oxidation of Thiocyanate by Periodate in Aqueous Alkaline Medium
- Kinetics and Mechanism of the Reactions of Bis(biguanide)copper(II) Ion with Different Amino Acids in Aqueous Media
- Keywords: Kinetics, copper(II), biguanide, amino acids, associative mechanism
- Aquation and Base Hydrolysis of trans-Tetraammine(methylamine)sulfatocobalt(III) Complex Ion
- Notes for Contributors. Inorganic Reaction Mechanisms
- Instructions for Authors
- Disk Specifications
