Molecules 2012, 17(1), 48-60; doi:10.3390/molecules17010048
Article

Influence of Halogen Substituents on the Catalytic Oxidation of 2,4,6-Halogenated Phenols by Fe(III)-Tetrakis(p-hydroxyphenyl) porphyrins and Potassium Monopersulfate

1 Laboratory of Chemical Resources, Division of Sustainable Resources Engineering, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan 2 Environmental Energy and Science, Graduate School of Science and Engineering for Research, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan 3 Low Level Radioactivity Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, Wake, Nomi-shi, Ishikawa 923-1224, Japan
* Author to whom correspondence should be addressed.
Received: 29 November 2011; in revised form: 17 December 2011 / Accepted: 19 December 2011 / Published: 22 December 2011
(This article belongs to the Special Issue Tetrapyrroles, Porphyrins and Phthalocyanine)
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Abstract: The influence of halogen substituents on the catalytic oxidation of 2,4,6-trihalogenated phenols (TrXPs) by iron(III)-porphyrin/KHSO5 catalytic systems was investigated. Iron(III)-5,10,15,20-tetrakis(p-hydroxyphenyl)porphyrin (FeTHP) and its supported variants were employed, where the supported catalysts were synthesized by introducing FeTHP into hydroquinone-derived humic acids via formaldehyde poly-condensation. F (TrFP), Cl (TrCP), Br (TrBP) and I (TrIP) were examined as halogen substituents for TrXPs. Although the supported catalysts significantly enhanced the degradation and dehalogenation of TrFP and TrCP, the oxidation of TrBP and TrIP was not enhanced, compared to the FeTHP catalytic system. These results indicate that the degree of oxidation of TrXPs is strongly dependent on the types of halogen substituent. The order of dehalogenation levels for halogen substituents in TrXPs was F > Cl > Br > I, consistent with their order of electronegativity. The electronegativity of a halogen substituent affects the nucleophilicity of the carbon to which it is attached. The levels of oxidation products in the reaction mixtures were analyzed by GC/MS after extraction with n-hexane. The most abundant dimer product from TrFP via 2,6-difluoroquinone is consistent with a scenario where TrXP, with a more electronegative halogen substituent, is readily oxidized, while less electronegative halogen substituents are oxidized less readily by iron(III)-porphyrin/KHSO5 catalytic systems.
Keywords: iron(III)-porphyrin; humic acid; hydroquinone; catalytic oxidation; 2,4,6-halogenated phenols; halogen substituent; electronegativity

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MDPI and ACS Style

Fukushima, M.; Mizutani, Y.; Maeno, S.; Zhu, Q.; Kuramitz, H.; Nagao, S. Influence of Halogen Substituents on the Catalytic Oxidation of 2,4,6-Halogenated Phenols by Fe(III)-Tetrakis(p-hydroxyphenyl) porphyrins and Potassium Monopersulfate. Molecules 2012, 17, 48-60.

AMA Style

Fukushima M, Mizutani Y, Maeno S, Zhu Q, Kuramitz H, Nagao S. Influence of Halogen Substituents on the Catalytic Oxidation of 2,4,6-Halogenated Phenols by Fe(III)-Tetrakis(p-hydroxyphenyl) porphyrins and Potassium Monopersulfate. Molecules. 2012; 17(1):48-60.

Chicago/Turabian Style

Fukushima, Masami; Mizutani, Yusuke; Maeno, Shouhei; Zhu, Qianqian; Kuramitz, Hideki; Nagao, Seiya. 2012. "Influence of Halogen Substituents on the Catalytic Oxidation of 2,4,6-Halogenated Phenols by Fe(III)-Tetrakis(p-hydroxyphenyl) porphyrins and Potassium Monopersulfate." Molecules 17, no. 1: 48-60.

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