• Resorcinol;
  • Chlorination;
  • Intermediate;
  • Pentachloride;
  • Mechanisms


The investigation reported here describes an attempt to establish the structure of the intermediate that undergoes ring-opening in the chlorination of resorcinol and its chloro-derivatives in a nucleophilic solvent such as H2O or CH3OH. The evidence suggests that the pentachloride and not the tetrachloride is the intermediate that reacts with the nucleophiles. Chlorination reactions were conducted in CH3OH/H2O. The structures of the “early-generation” products from incorporation of CH3OH were sufficiently stable to be characterized. These products implicated the pentachloride. Resorcinol, di- and trichlororesorcinol, and the pentachloride gave the same products. The mechanisms of the ring-opening and the reactions leading to the products are described in detail. The assumption is made that the same or similar reactions are involved in the aqueous chlorination of resorcinol, but that decarboxylation and solvolysis reactions rapidly degrade the products immediately following ring-opening.