Kinetics of the oxidation of quercetin by 2,2-diphenyl-1-picrylhydrazyl (dpph•)

Org Lett. 2011 Sep 16;13(18):4826-9. doi: 10.1021/ol2019086. Epub 2011 Aug 16.

Abstract

In methanol/water, dpph(•) bleaching (519 nm) by quercetin, QH(2), exhibits biphasic kinetics. The dpph(•) reacts completely with the quercetin anion within 100 ms. Subsequent slower bleaching involves solvent and QH(2) addition to quinoid products. The fast reaction is first-order in dpph(•) but only ca. 0.38 order in [QH(2)]. This extraordinary nonintegral order is attributed to reversible formation of π-stacked {QH(-)/dpph(•)} complexes in which electron transfer to products, {QH(•)/dpph(-)}, is slow (k(ET) ≈ 10(5) s(-1)).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biphenyl Compounds / chemistry*
  • Kinetics
  • Methanol / chemistry
  • Models, Molecular
  • Molecular Structure
  • Oxidation-Reduction
  • Picrates / chemistry*
  • Quercetin / chemistry*
  • Stereoisomerism
  • Water / chemistry

Substances

  • Biphenyl Compounds
  • Picrates
  • Water
  • Quercetin
  • 1,1-diphenyl-2-picrylhydrazyl
  • Methanol