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The halogenation reactions of 1,3-dihydroxyaromatic compounds and simple methyl ketones in dilute aqueous solution have been investigated in order to elucidate the mechanism of analogous processes involving naturally occurring humic material. The 1,3-dihydroxyaromatic model compounds were most reactive with maximum yields of CHC13 (>90%) and CHBr3 (>70%) at pH 8-10 with substrate concentrations of 10"® M and halogen concentrations of 10"5-10"4 M. At high chlorine concentrations, substantial yields of a variety of Cl-substituted carboxylic acids were detected, whereas at low [Cl2] values, a number of important polyhalogenated reaction intermediates were identified. Halogenation of resorcinol-2-13C produced 13CHC13 and 13CHBr3 with isotopic enrichments equivalent to that of the labeled precursor. The experimental data are generally consistent with a dominant haloform-type reaction mechanism, but some details of these results strongly suggest that several competitive pathways are also involved.

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