Reduction of Crystal Violet by Diphenylketyl Radicals

Article abstract of DOI:10.1021/ja00261a021

Crystal violet (CV⁺) is stable to direct photolysis in acetonitrile at λ_irr >/= 366 nm even in the presence of hydrogen donors (benzhydrol and 2-propanol).However, when benzophenone (K) is present in samples containing hydrogen donor and λ_irr + by diphenylketyl (KH^.) followed by hydrogen transfer to the intermediate CV^. with formation of the leuco dye (CVH) is proposed.The rate constant (k₆) for the electron transfer reaction CV⁺ + KH^. -> CV^. + K + H⁺, k₆ = 6 +/- 2 x 10⁵ M^-1 s^-1 (6) has been determined by two methods both of which rely on the competition between reactions 5 and 6 2KH^. -> K₂H₂, k₅ = 1.05 +/- 0.02 x 10⁸ M^-1 s^-1 (5) In the first the quantum yield of sensitized fading is determined as a function of CV⁺ concentration.In the second the rates of benzpinacol formation in the absence and presence of CV⁺ are followed.