Redox, kinetics, and complexation chemistry of the CrVI/CrV/CrIV -D-glycero-D-gulo-heptono-1,4-lactone System

Autor:	María Florencia Mangiameli, Silvia García, Juan Carlos González, Ana María Atria, Sebastián Bellú, María Inés Frascaroli, Juan Manuel Salas Peregrín, Evangelina Caffaratti, Mabel Santoro, Luis F. Sala
Rok vydání:	2010
Předmět:	chemistry.chemical_classification Chemistry Formic acid Radical Organic Chemistry Inorganic chemistry Reactive intermediate Kinetics chemistry.chemical_element Redox Medicinal chemistry law.invention chemistry.chemical_compound Chromium law Physical and Theoretical Chemistry Electron paramagnetic resonance Lactone
Zdroj:	Journal of Physical Organic Chemistry. 23:960-971
ISSN:	0894-3230
DOI:	10.1002/poc.1745
Popis:	When a 60-times or higher excess of D-glycero-D-gulo-heptono-1,4-lactone (GHL) over CrVI is used, reaction yields D-gluconic acid, formic acid and CrIII as final products. The redox reaction involves formation of intermediates, CrIV and CrV species, reacting with GHL at comparable rates. CrIV is a very reactive intermediate and does not accumulate during this reaction; its rate of disappearance is 2.0 × 104 and 4.0 × 103 times higher than CrVI or CrV reaction with GHL, respectively. Kinetic studies show that the redox reaction proceeds through a mechanism combining CrVI CrIV CrII and CrVI CrIV CrIII pathways. This mechanism is supported by the observation of free radicals, superoxoCrIII (CrO) and oxo-CrV as intermediates species. Complete rate laws for the GHL/chromium redox reaction are described in the present work. EPR spectra show that five-coordinate oxo-CrV bischelates (giso1 = 1.9802; giso2 = 1.9803) are formed at pH ≤ 4 where the OH and O-ring groups of GHL participate in the bonding to oxo-CrV. Penta-coordinated oxo-CrV monochelates are observed as minor species (giso3 = 1.9866; giso4 = 1.9879) in addition to the major penta-coordinated oxo-CrV bischelates. Copyright © 2010 John Wiley & Sons, Ltd.
Databáze:	OpenAIRE
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