In the classical view of electrophilic aromatic substitution of a phenol, an intermediate involving a dieneone is produced. This intermediate is thought to rapidly rearomatize to form the chlorinated phenol.  In the chlorination of the polyphenol resorcinol by hypochlorous acid, Rebenne, et al. (Env. Sci. & Tech, 1996) have reported rate constants for multiple chlorination steps that would be appropriate assuming a sequential chlorination mechanism involving a rapid rearomatization. However, Heasley, et al. (Env. Tox. & Chem, 1989) report the predominance of trichlorinated product even when there is a single molar equivalent of chlorine to resorcinol. This is inconsistent with a sequential mechanism involving rapid rearomatization. The reaction between resorcinol and hypochlorous acid has been investigated using stopped flow techniques.  The data suggest that the dieneone intermediate may not always rearomatize prior to reacting with additional hypochlorous acid.  The results of these experiments will be the subject of this presentation.

Investigations into the mechanism of the chlorination of resorcinol by hypochlorous acid

245th National Meeting (2013)

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