Medium Effect on Tetrahydroxy-1,4-Benzoquinone

Chemistry Department, Faculty of Science, Assiut University, Assiut, Egypt Manuscript received 24 July 1979, accepted 7 August 1980 The electronic absorption spectra of tetrahydroxy-p-benzoquinone (THBQ) are studied in organic solvents of different polarities, in mixed organic solvents and in aqueous solutions of varying pH's. The different types of interaction liable to occur in solution are discussed. The ability of the compound to form molecular complexes in ethanol media is investigated. The spectral changes with pH indicates that the four OH — groups are ionised simultaneously and only an overall pK value is obtained. The possibility of multistep ionisation is investigated by studying the titration behaviour of the compound at different ethanol concentrations