| Abstract | The equilibria between 2,2,6,6-tetramethylpiperidyl-1-thiyl and diisopropylaminothiyl and the corresponding bis(dialkylamino) disulfides have been examined by EPR spectroscopy: R2NSSNR2 ⇌ 2R2NS (k1, k-1). Within experimental error, the equilibrium constants are the same for both radicals (ΔS = 23 ± 4 gibbs/mol, ΔH = 27 ± 2 kcal/mol), as are the rate constants for disulfide decomposition and radical combination which can be represented, respectively, by log (k1/sec-1) = 16.8 - 31/θ and log (k-1/M-1 sec-1) = 11.8 - 4.0/0, where θ = 2.3RT kcal/mol. These radicals were generated in solution both thermally and photochemically, but photolysis in solid matrices at low temperatures gives some N-S bond scission. Dialkylaminothiyl radicals are unreactive toward a variety of molecular substrates. The first sulfur analogue of an iminoxy radical, diphenyliminothiyl, has been generated by photolysis of the corresponding disulfide. Its EPR parameters are g = 2.0152, aN = 18.16 G. |
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