Small-Ring Compounds. XXV. Phenylcyclobutadienoquinone and Related Compounds

Abstract

Thermal addition of phenylacetylene to trifluorochloroethylene and tetrafluoroethylene followed by hydrolysis of either product with concentrated sulfuric acid has led to the formation of phenylcyclobutene-1,2-dione(phenylcyclobutadienoquinone). This compound proved to be quite stable and displayed some unusual properties. A number of its substitution products have been prepared and their properties are described. Of these, 4-hydroxy-3-phenylcyclobutene-1,2-dione was of special interest in being a remarkably strong acid with pK_a of 0.37. The stability of phenylcyclobutadienoquinone and the acid strength of the 4-hydroxy derivative are discussed and correlated with delocalization energies calculated by the LCAO method.

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