Kinetics and Mechanism of the oxidation of D-galactono-1,4 Lactone by Chromium(VI) and Chromium(V)

S. SIGNORELLA; M. SANTORO; C. PALOPOLI; C.D. BRONDINO; J. M. SALAS-PEREGRIN; M. QUIROS; L. F. SALA

POLYHEDRON

PERGAMON-ELSEVIER SCIENCE LTD

Año: 1998 vol. 17 p. 2739 - 2749

0277-5387

The oxidation of D!galactono!0\3!lactone by CrVI yields D!lyxonic acid\ carbon dioxide and Cr2 as _nal products when an excess of sugar acid over CrVI is used[ The redox reaction occurs through CrVI: CrIII and CrVI:CrV:CrIII paths[ The complete rate law for the CrVI oxidation reaction is expressed by dCrVI:dt"k9kH H# galCrVI\ where k9"2022#093 M0 s0 and kH"8824#093 M1 s0\ at 39>C[ CrV is formed in a rapid step by reaction of the CO=1 radical with CrVI[ CrV reacts with the substrate faster than does CrVI[ The CrV oxidation follows the rate law ] dCrV:dt"k?9k?H H# gal\ where k?9"0421#092 M0 s0 and k?H"2323#092 M1 s0\ at 39>C[ The EPR spectra show that several intermediate Cr"O#"gala#1 linkage isomers are formed in rapid pre!equilibria before the redox steps.