Identification of intermediates leading to chloroform and C-4 diacids in the chlorination of humic acid

Abstract

The chlorination of terrestrial humic acid was studied at pH 7. 2 with varying chlorine to carbon ratios. The principal products are chloroform, di- and trichloroacetic acid, and chlorinated C-4 diacids. At a high chlorine dose many new chlorination products were detected, among them chlorinated aromatic acids. At a low chlorine dose a class of chlorinated compounds was found, which contained a trichloromethyl group. These compounds may be converted into chloroform and in most eases C-4 diacids by oxidation and hydrolysis reactions. Because these compounds are found mainly at low chlorine dosage, they may be regarded as intermediates in the reactions that give chloroform. The intermediates support the hypothesis of Rook that m-dihydroxybenzene moieties in humic acid are responsible for the formation of chloroform. A reaction scheme is proposed that explains the formation of the intermediates.