| Résumé | The title radical, Ph 2P(O)O •, has been generated by laser flash photolysis (LPP) of the peroxide [Ph 2P(O)O] 2 (1) in CH 3CN solution. It has a broad, structureless absorption extending from 400 to beyond 800 mn. Absolute bimolecular rate constants k for its reactions with various organic substrates have been measured by LFP. It has been found that Ph 2P(O)O • is more reactive in hydrogen abstraction (e.g., cyclohexane, k = 2.4 × 10 8 M -1 s -1) and addition (e.g., benzene, k = 9.1 7times; 10 8 M -1 s -1) than any other organic oxygen-centered radical. Only HO • is (generally) more reactive. Although Ph 2P(O)O • could not be directly detected by EPR spectroscopy, it was successfully spin-trapped with a nitrone and with alkenes and alkynes. The formation of Ph 2P(O)O • in the photodecomposition but not in the thermal decomposition of 1 is supported by 31P NMR analyses of reaction products. Semiempirical AM1-PM3 calculations on H 2P(O)O • are also reported. |
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