Oxidation of 1-naphthol and related phenols with hydrogen peroxide and potassium superoxide catalysed by 5,10,15,20-tetraarylporphyrinatoiron(III)chlorides in different reaction conditions

Chauhan, S. M. S.; Kalra, Bhanu; Mohapatra, Prabhu P.

doi:10.1016/s1381-1169(98)00079-x

Cited by 40 publications

(6 citation statements)

References 24 publications

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“…According to the observed surface reaction kinetics, identified products, and the published information on the oxidation of phenolic and substituted phenolic compounds mentioned previously [30,38–40], we propose a tentative reaction scheme for the PCP oxidation by MnO 2 (Fig. 6).…”

Section: Resultsmentioning

confidence: 59%

Oxidation kinetics of pentachlorophenol by manganese dioxide

Zhao

Peng

et al. 2006

Environmental Toxicology and Chemistry

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This study examined the abiotic transformation kinetics of pentachlorophenol (PCP) by manganese dioxide (MnO2) at different solution chemistry and initial concentrations of PCP and MnO2. The measured PCP transformation rates were found to be on the order of 1.07 with respect to [PCP] and 0.91 and 0.87 with respect to [MnO2] and [H+], respectively. Dissolved Mn2+ and Ca2+ as background electrolytes considerably decreased the reaction rate because of their adsorption and hence blocking of active sites on MnO2 surfaces. The dechlorination number, 0.59 chloride ions per transformed PCP after a 1-h reaction, suggests that a fraction of the transformed PCP was not dechlorinated and may be coupled directly to dimeric products. Gas chromatography/ mass spectrometry and liquid chromatography/mass spectrometry/mass spectrometry techniques were used to identify two isomeric nonachlorohydroxybiphenylethers as major products and 2,3,5,6-tetrachloro-1,4-hydroquinone and tetrachlorocatechol as minor products. Product identification suggested that the reaction may include two parallel reactions to form either dimers or 2,3,5,6-tetrachloro-1,4-hydroquinone and tetrachlorocatechol via simultaneous dehydrochlorination and hydroxylation.

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Section: Resultsmentioning

confidence: 59%

Oxidation kinetics of pentachlorophenol by manganese dioxide

Zhao

Peng

et al. 2006

Environmental Toxicology and Chemistry

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“…Reaction Schemes. On the basis of the observed surface reaction kinetics, product identification, and literature on the oxidation of phenolic compounds by oxygen and metal complexes ( − ), the reaction scheme for triclosan oxida tion by manganese oxide is proposed in Figure . Initially triclosan is bound to the surface Mn IV to form a precursor complex.…”

Section: Resultsmentioning

confidence: 99%

Oxidative Transformation of Triclosan and Chlorophene by Manganese Oxides

Zhang

Huang

2003

Environ. Sci. Technol.

345

316

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The antibacterial agents triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) and chlorophene (4-chloro-2-(phenylmethyl)phenol) show similar susceptibility to rapid oxidation by manganese oxides (delta-MnO2 and MnOOH) yielding Mn(II) ions. Both the initial reaction rate and adsorption of triclosan to oxide surfaces increase as pH decreases. The reactions are first-order with respect to the antibacterial agent and MnO2. The apparent reaction orders to H+ were determined to be 0.46 +/- 0.03 and 0.50 +/- 0.03 for triclosan and chlorophene, respectively. Dissolved metal ions (Mn(II), Zn(II), and Ca(II)) and natural organic matter decrease the reaction rate by competitively adsorbing and reacting with MnO2. Product identification indicates that triclosan and chlorophene oxidation occurs at their phenol moieties and yields primarily coupling and p-(hydro)quinone products. A trace amount of 2,4-dichlorophenol is also produced in triclosan oxidation, suggesting bond-breaking of the ether linkage. The experimental results support the mechanism that after formation of a surface precursor complex of the antibacterial agent and the surface-bound Mn(IV), triclosan and chlorophene are oxidized to phenoxy radicals followed by radical coupling and further oxidation to form the end products. Compared to several structurally related substituted phenols (i.e., 2-methyl-4-chlorophenol, 2,4-dichlorophenol, 3-chlorophenol, and phenol), triclosan and chlorophene exhibit comparable or higher reactivities toward oxidation by manganese oxides. The higher reactivities are likely affected by factors including electronic and steric effects of substituents and compound hydrophobicity. Once released into the environment, partitioning of triclosan and chlorophene to soils and sediments is expected because of their relatively hydrophobic nature. Results of this study indicate that manganese oxides in soils will facilitate transformation of these antibacterial agents.

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“…A variety of substituted quinolines, including 8-hydroxyquinoline, that is prone to phenolic oxidation, 42 have undergone a smooth and chemoselective transformation to the corresponding N -oxides. Similarly, substituted pyridines are also viable substrates for the reaction.…”

Section: Resultsmentioning

confidence: 99%

Insights into the mechanistic and synthetic aspects of the Mo/P-catalyzed oxidation of N-heterocycles

et al. 2014

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A Mo/P catalytic system for an efficient gram-scale oxidation of a variety of nitrogen heterocycles to N-oxides with hydrogen peroxide as terminal oxidant has been investigated. Combined spectroscopic and crystallographic studies point to the tetranuclear Mo4P peroxo complex as one of the active catalytic species present in the solution. Based on this finding an optimized catalytic system has been developed. The utility and chemoselectivity of the catalytic system has been demonstrated by the synthesis of over 20 heterocyclic N-oxides.

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Oxidation of 1-naphthol and related phenols with hydrogen peroxide and potassium superoxide catalysed by 5,10,15,20-tetraarylporphyrinatoiron(III)chlorides in different reaction conditions

Cited by 40 publications

References 24 publications

Oxidation kinetics of pentachlorophenol by manganese dioxide

Oxidation kinetics of pentachlorophenol by manganese dioxide

Oxidative Transformation of Triclosan and Chlorophene by Manganese Oxides

Insights into the mechanistic and synthetic aspects of the Mo/P-catalyzed oxidation of N-heterocycles

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