Chromium(V) Peptide Complexes: Synthesis and Spectroscopic Characterization
作者:Peter J. Barnard、Aviva Levina、Peter A. Lay
DOI:10.1021/ic048322h
日期:2005.2.1
covalently bound to the amine group of the peptide ligand, yielding a urea group, and a third coordinated deprotonated urea nitrogen donor. A metal-directed oxidative coupling has been proposed as a possible mechanism for the organic transformation. The Cr(V/IV) reduction potential was determined for the three Cr(V) complexes using cyclic voltammetry, and in all cases it was quasi-reversible. These are the first
Chromium(V) Complexes of Hydroxamic Acids: Formation, Structures, and Reactivities
作者:Swetlana Gez、Robert Luxenhofer、Aviva Levina、Rachel Codd、Peter A. Lay
DOI:10.1021/ic048317d
日期:2005.4.1
A new family of relatively stable Cr(V) complexes, [Cr(V)O(L)(2)](-) (LH(2) = RC(O)NHOH, R = Me, Ph, 2-HO-Ph, or HONHC(O)(CH(2))(6)), has been obtained by the reactions of hydroxamic acids with Cr(VI) in polar aprotic solvents. Similar reactions in aqueous solutions led to the formation of transient Cr(V) species. All complexes have been characterized by electron paramagnetic resonance spectroscopy
Characterization and oxidation of chromium(III) by sodium hypochlorite in alkaline solutions
作者:Huijian Jiang、Linfeng Rao、Zhicheng Zhang、Dhanpat Rai
DOI:10.1016/j.ica.2006.03.035
日期:2006.7
caustic leaching or oxidation of Cr(III) to Cr(VI). The objective of this study is to investigate the effect of oligomerization of Cr(III) on its oxidation by hypochlorite in alkalinesolutions. Monomeric, dimeric and trimeric Cr(III) species in solution were separated by ion exchange. The kinetics of the oxidation of the separated species by hypochlorite in alkalinesolutions was studied by UV/Vis
A Light Reaction with Negative Temperature Coefficient
作者:K. WEBER、S. AŠPERGER
DOI:10.1038/157373b0
日期:1946.3.23
With increasing temperature this equilibrium is displaced in such a manner that the concentration of one of the reacting components diminishes, and, consequently, the resulting reaction velocity decreases. It is evident that a negative temperaturecoefficient is more easily attained the more the equilibrium depends on the rise of temperature and the less the velocity-determining reaction depends on it
CrO42− anion and a relatively stable Cr(V) complex. Consecutive biphasic kinetics through two first-order steps were observed for the base hydrolysis and the oxidation process, whereas the acid-catalyzed aquation obeys a simple first-order pattern. Based on the kinetic and spectroscopic data, mechanisms of the coordinated amino acid liberation and chromium(III) oxidation are discussed.