Résumé | The reactions between triplet diphenylcarbene and fluorenylidene with a variety of sulphides and disulfides were investigated with use of electron paramagnetic resonance (EPR) spectroscopy, laser flash photolysis, and product studies. Diphenylcarbene reacted with these substrates by a radical-like displacement mechanism. Rate constants were ca. 10⁶ M⁻1 s⁻1, and the resulting thio-substituted diphenylmethyl radicals were identified by their EPR and optical spectra. By contrast, the analogous reactions of fluorenylidene had rate constants of 10⁸-10⁹ M⁻¹ s⁻¹ and proceeded by an ylide mechanism. Product studies were consistent with these results but were not sufficient in themselves to reveal these mechanistic differences. |
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