Kinetics and mechanism of Ru(III) and Hg(II) co-catalyzed oxidation of D-galactose and D-ribose by N-bromoacetamide in perchloric acid.
Kinetics of oxidation of reducing sugars D-galactose (Gal) and D-ribose (Rib) by N-bromoacetamide (NBA) in the presence of ruthenium(III) chloride as a homogeneous catalyst and in perchloric acid medium, using mercuric acetate as a scavenger for Br(minus sign) ions, as well as a co-catalyst, have been investigated. The kinetic results indicate that the first-order kinetics in NBA at lower concentrations tend towards zero order at its higher concentrations. The reactions follow identical kinetics, being first order in the [sugar] and [Ru(III)]. Inverse fractional order in [H(+)] and [acetamide] were observed. A positive effect of [Hg(OAc)(2)] and [Cl(minus sign)] was found, whereas a change in ionic strength (mu) has no effect on oxidation velocity. Formic acid and D-lyxonic acid (for Gal) and formic acid and L-erythronic acid (for Rib) were identified as main oxidation products of reactions. The various activation parameters have been computed and recorded. A suitable mechanism consistent with experimental findings has been proposed.
Singh
Ashok Kumar
AK
Department of Chemistry, University of Allahabad, 211 002, Allahabad, India. ashokeks@rediffmail.com
Singh
Vineeta
V
Singh
Ajaya Kumar
AK
Gupta
Neena
N
Singh
Bharat
B
D000081:Acetamides / Q000737:chemistry*; D002087:Butyrates / Q000737:chemistry; D002384:Catalysis; D005561:Formates / Q000737:chemistry; D005690:Galactose / Q000737:chemistry*; D008628:Mercury / Q000737:chemistry*; D010084:Oxidation-Reduction; D010472:Perchlorates / Q000737:chemistry*; D012266:Ribose / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D013400:Sugar Acids / Q000737:chemistry
D000081:Acetamides; D002087:Butyrates; D005561:Formates; D010472:Perchlorates; D013400:Sugar Acids; C121691:erythronic acid; C016272:N-bromoacetamide; C030544:formic acid; C092647:lyxonic acid; D012266:Ribose; D012428:Ruthenium; D008628:Mercury; D005690:Galactose