OXIDATION AND DECHLORINATION OF CHLOROPHENOLS IN DILUTE AQUEOUS SUSPENSIONS OF MANGANESE OXIDES - REACTION-PRODUCTS

Some monomeric and dimeric oxidation products of para- and/or ortho-chlorinated phenols in dilute (1 mmol/L phenol), acidified, aqueous suspensions of manganese oxide (Na-buserite) were identified by MS, Fourier-transform IR spectroscopy and UV/visible spectroscopy. The para-chlorinated phenols (4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 4-chloro-2-methylphenol) gave corresponding p-benzoquinones (benzoquinone, 2-chlorobenzoquinone, 2,6-dichlorobenzoquinone, 2-methylbenzoquinone) as the detectable water-soluble oxidation products. Dimeric products were present in the extracts obtained by washing the oxide with methylene chloride. Michael addition of phenolate to quinone seems to be the predominant mode of coupling. Chlorinated phenols without chlorine in the para-position (2-chlorophenol, 2,6-dichlorophenol) were more difficult to oxidize and afforded diphenoquinones as the only detectable water-soluble products. For all studied phenols, with the exception of 2,4,6-trichlorophenol, the amount of water-soluble products accounts only for a small fraction of oxidized phenol. The quinone and diphenoquinone products readily couple with phenols into humuslike materials.