(2Z)-2,3,4,5,5-Pentachloropenta-2,4-dienic acid as a minor product in the synthesis of 5,5-dimetoxytetrachlorocyclopentadiene from hexachlorocyclopentadiene

Abstract

Pentachloropentadienic acid was isolated, apart from the expected 5,5-dimetoxytetrachlorocyclopentadiene, in the reaction of hexachlorocyclopentadiene with potassium hydroxide in methanol. The structure of this minor product was established by X-ray crystallography. The plausible mechanism of its formation is discussed.