Journal article
Reaction of phenol with singlet oxygen
Physical Chemistry Chemical Physics, Vol.21(1), pp.171-183
2019
Abstract
Photo-degradation of organic pollutants plays an important role in their removal from the environment. This study provides an experimental and theoretical account of the reaction of singlet oxygen O2(1Δg) with the biodegradable-resistant species of phenol in an aqueous medium. The experiments combine customised LED-photoreactors, high-performance liquid chromatography (HPLC), and electron paramagnetic resonance (EPR) imaging, employing rose bengal as a sensitiser. Guided by density functional theory (DFT) calculations at the M062X level, we report the mechanism of the reaction and its kinetic model. Addition of O2(1Δg) to the phenol molecule branches into two competitive 1,4-cycloaddition and ortho ene-type routes, yielding 2,3-dioxabicyclo[2.2.2]octa-5,7-dien-1-ol (i.e., 1,4-endoperoxide 1-hydroxy-2,5-cyclohexadiene) and 2-hydroperoxycyclohexa-3,5-dien-1-one, respectively. Unimolecular rearrangements of the 1,4-endoperoxide proceed in a facile exothermic reaction to form the only experimentally detected product, para-benzoquinone. EPR revealed the nature of the oxidation intermediates and corroborated the appearance of O2(1Δg) as the only active radical participating in the photosensitised reaction. Additional experiments excluded the formation of hydroxyl (HO˙), hydroperoxyl (HO2˙), and phenoxy intermediates. We detected for the first time the para-semibenzoquinone anion (PSBQ), supporting the reaction pathway leading to the formation of para-benzoquinone. Our experiments and the water-solvation model result in the overall reaction rates of kr-solvation = 1.21 × 104 M−1 s−1 and kr = 1.14 × 104 M−1 s−1, respectively. These results have practical application to quantify the degradation of phenol in wastewater treatment.
Details
- Title
- Reaction of phenol with singlet oxygen
- Authors/Creators
- J. Al-Nu’airat (Author/Creator) - Murdoch UniversityB.Z. Dlugogorski (Author/Creator) - Murdoch UniversityX. Gao (Author/Creator) - Murdoch UniversityN. Zeinali (Author/Creator) - Murdoch UniversityJ. Skut (Author/Creator) - Murdoch UniversityP.R. Westmoreland (Author/Creator) - North Carolina State UniversityI. Oluwoye (Author/Creator) - Murdoch UniversityM. Altarawneh (Author/Creator) - Murdoch University
- Publication Details
- Physical Chemistry Chemical Physics, Vol.21(1), pp.171-183
- Publisher
- Royal Society of Chemistry
- Identifiers
- 991005543233907891
- Copyright
- © 2019 Royal Society of Chemistry
- Murdoch Affiliation
- School of Engineering and Information Technology
- Language
- English
- Resource Type
- Journal article
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- Collaboration types
- Domestic collaboration
- International collaboration
- Citation topics
- 2 Chemistry
- 2.59 Pigments, Sensors & Probes
- 2.59.735 Photodynamic Therapy
- Web Of Science research areas
- Chemistry, Physical
- Physics, Atomic, Molecular & Chemical
- ESI research areas
- Chemistry