Degradative Pathways for Aqueous Chlorination of Orcinol

The reaction mechanisms for aqueous chlorination of orcinol and other model compounds of natural humic substances were studied using gas chromatography-mass spectrometry (GC-MS) analysis of products and intermediates. The experiments were conducted at chlorine to substrate molar ratios from 1:2 to 4:l and neutral pHs. Longer reaction times led to the increased production of oxidized products and the disappearance of polychlorinated products due to slow hydrolysis reactions. Chlorination of orcinol gave rise to more than 40 reaction products and intermediates, including chlorinated orcinols, noncyclic and cyclic chlorinated ketones, carbonic acids, ketoacids, lactones, and furanones. Proposed reaction schemes are suggested for the degradation of orcinol in water with chlorine, which can be used to explain the reactivity of humic substances upon chlorination and account for the presence of known disinfection byproducts, such as MX and other chlorinated furanones.