Redox interactions between structurally different alkylresorcinols and iron(III) in aqueous media: Frozen-solution 57Fe Mössbauer spectroscopic studies, redox kinetics and quantum chemical evaluation of the alkylresorcinol reactivities

Alexander A. Kamnev, Roman L. Dykman, Krisztina Kovács, Alexei N. Pankratov, Anna V. Tugarova, Zoltán Homonnay, Erno Kuzmann

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Abstract

Iron(III)-containing aqueous solutions of 5-methylresorcinol (5-MR), 5-n-propylresorcinol (5-n-PR) and 4-n-hexylresorcinol (4-n-HR) at pH ~ 3 were studied by means of 57Fe transmission Mössbauer spectroscopy. Kinetic considerations were applied to the redox reactions. Density Functional Theory (DFT) calculations were performed for the alkylresorcinol (AR) molecules and their non-alkylated analogue (resorcinol). Mössbauer spectra consisted of quadrupole doublets assigned to high-spin Fe(III) and Fe(II) species. From changes in their relative spectral areas, a gradual reduction of Fe(III) by all the ARs studied was observed. However, significant differences were found for the reduction rates among the ARs. The following series of the reduction rates was established by means of Mössbauer spectroscopy: 4-n-HR 5-MR > 5-n-PR, supplemented by rate constants calculated using a kinetic model. DFT calculations resulted in the following series: 4-n-HR 5-n-PR > 5-MR resorcinol (the latter is not oxidised under the conditions applied). The reversed order of the experimentally observed 5-MR and 5-n-PR oxidation rates may be explained in terms of their different kinetic parameters related to their structure.

Original languageEnglish
Pages (from-to)649-657
Number of pages9
JournalStructural Chemistry
Volume25
Issue number2
DOIs
Publication statusPublished - Apr 2014

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Keywords

  • Alkylresorcinols
  • DFT calculations
  • Iron(III) reduction
  • Redox kinetics

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

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