Dynamics of proton tautomerism in 2,5-dihydroxy-p-benzoquinone: A ¹³C NMR and CNDO study

The temperature and solvent dependence of the 13C NMR spectra of 2,5-dihydroxy-p-benzoquinone have been investigated. The variations of the line shapes are analyzed in terms of chemical exchange of the two equivalent intramolecular hydrogen bonds. The interpretation of the rate parameters suggests an interconversion mechanism in which the two hydroxylic protons move in a two consecutive step mechanism. This is supported by the shape of the potential surface for the motion of the hydroxylic protons, calculated by CNDO. © 1979.