Choice of a suitable hetero-aromatic nitrogen base as promoter for chromic acid oxidation of dl-mandelic acid in aqueous media at room temperature

Choice of a suitable hetero-aromatic nitrogen base as promoter for chromic acid oxidation of... Chromic acid oxidation of dl-mandelic acid in the presence and absence of different promoters has been studied in aqueous media under the kinetic conditions [mandelic acid]T ≫ [Cr(VI)]T and [promoter]T ≫ [Cr(VI)]T at 30 °C. The promoters used in this oxidation reaction, picolinic acid (PA), 2,2′-bipyridine (bpy), and 1,10-phenanthroline (phen), are strong chelating ligands which form complexes with most transition metal ions. The reaction is first-order with regard to [H+], [mandelic acid]T, and [Cr(VI)]T and also has first-order dependence on [promoter]T. HCrO4 − was found to be kinetically active in the absence of promoters; in the presence of promoters the Cr(VI)–promoter complexes were believed to be the active oxidants. In this path the Cr(VI)-promoter complex in each case undergoes nucleophilic attack by the mandelic acid to form a ternary complex which subsequently undergoes redox decomposition involving 3e transfer as the rate-determining step. Among the three promoters oxidation is much faster with 1,10-phenanthroline. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Research on Chemical Intermediates Springer Journals

Choice of a suitable hetero-aromatic nitrogen base as promoter for chromic acid oxidation of dl-mandelic acid in aqueous media at room temperature

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Publisher
Springer Netherlands
Copyright
Copyright © 2012 by Springer Science+Business Media B.V.
Subject
Chemistry; Catalysis; Physical Chemistry; Inorganic Chemistry
ISSN
0922-6168
eISSN
1568-5675
D.O.I.
10.1007/s11164-012-0585-y
Publisher site
See Article on Publisher Site

Abstract

Chromic acid oxidation of dl-mandelic acid in the presence and absence of different promoters has been studied in aqueous media under the kinetic conditions [mandelic acid]T ≫ [Cr(VI)]T and [promoter]T ≫ [Cr(VI)]T at 30 °C. The promoters used in this oxidation reaction, picolinic acid (PA), 2,2′-bipyridine (bpy), and 1,10-phenanthroline (phen), are strong chelating ligands which form complexes with most transition metal ions. The reaction is first-order with regard to [H+], [mandelic acid]T, and [Cr(VI)]T and also has first-order dependence on [promoter]T. HCrO4 − was found to be kinetically active in the absence of promoters; in the presence of promoters the Cr(VI)–promoter complexes were believed to be the active oxidants. In this path the Cr(VI)-promoter complex in each case undergoes nucleophilic attack by the mandelic acid to form a ternary complex which subsequently undergoes redox decomposition involving 3e transfer as the rate-determining step. Among the three promoters oxidation is much faster with 1,10-phenanthroline.

Journal

Research on Chemical IntermediatesSpringer Journals

Published: May 29, 2012

References

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