Reaction of the 2-hydroxy-2-propyl radical with acrylate type molecules in aqueous solution: Radical addition or electron transfer

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Abstract

The reaction of 2-hydroxy-2-propyl (IP) radical with 12 acrylate type monomers in aqueous solutions was investigated by means of pulse radiolysis: the molecular structure effects and the mechanisms were evaluated. Radicals were generated either in the reaction of hydrated electron with acetone and subsequent protonation or in the H abstraction reaction by OH radicals from i-propanol. IP radical reacts with acrylamides and acrylic acid esters in radical addition reaction of the type: (CH3)2(OH)C{radical dot} + CH2{double bond, long}CH-C(O)R → (CH3)2(OH)C-CH2-C{radical dot}H-C(O)R with rate coefficients between 3.2 × 107 and 1.9 × 108 mol-1 dm3 s-1. Rate coefficients of the reaction with maleic acid (neutral), dimethyl- and diethyl maleate are between 1.3 × 108 and 4.7 × 108 mol-1 dm3 s-1. The values for dimethyl- and diethyl fumarate are ca. one order of magnitude higher. However with maleates and fumarates there is also a few percent contribution from the electron transfer reaction of the type (CH3)2(OH)C{radical dot} + ROOC-CH{double bond, long}CH-COOR + H2O → ROOC-CH{double bond, long}CH-C{radical dot}O-OR + (CH3)2CO + H3O+. In neutral solutions and at pH ∼3 and ∼9, the same rate coefficients were measured. However, in dialkyl maleate and -fumarate solutions between pH 9.5 and 10.5, a base catalyzed decomposition of the IP radical adduct was observed forming electron adduct: ROOC-C((CH3)2(OH)C)H-C{radical dot}H-COOR + OH- → ROOC-CH{double bond, long}CH-C{radical dot}O-OR + (CH3)2CO + H2O. Molecular structure effects were evaluated using log k-σp and log k-LUMO plots.

Original languageEnglish
Pages (from-to)335-343
Number of pages9
JournalChemical Physics
Volume327
Issue number2-3
DOIs
Publication statusPublished - Sep 11 2006

Keywords

  • 2-Hydroxy-2-propyl radical
  • Acrylamides
  • Acrylic acid esters
  • Electron transfer
  • Fumaric acid
  • Maleic acid
  • Radical addition

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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