On the existence of quinone radical cations. A study in 1,1,1,3,3,3-hexafluoropropan-2-ol

The strongly stabilizing influence of 1,1,1,3,3,3-hexafluoropropan-2-ol (HFP) upon radical cations has been utilized to study the photolysis of a few quinones (Q), viz. benzoquinone, duroquinone, anthraquinone and tetrafluorobenzoquinone, in HFP containing 6% trifluoroacetic acid. The EPR spectra of the photolysed solutions are assigned to the radical cations of the corresponding hydroquinones (QH(2)(.+), the three first-mentioned quinones) or the protonated semiquinone (QH(.), the tetrafluoro derivative), formed in a one-electron redox process involving excited Q as the reductant, in agreement with earlier studies in strongly acidic media.