Matrix Isolation and Spectroscopic Characterization of the Phenylperoxy Radical and Its Rearranged Products

The phenylperoxy radical 1 has been synthesized by the reaction of the phenyl radical 2 with (3)O(2). Radical 1 could be either generated in the gas phase and subsequently trapped in solid argon at 10 K, or directly synthesized in argon matrices. By reacting 2 as well as its perdeuterated isotopomer [D(5)]-2 with (16)O(2) and with (18)O(2), respectively, the four isotopomers [H(5)]-(16)O(2)-1, [D(5)]-(16)O(2)-1, [H(5)]-(18)O(2)-1, and [D(5)]-(18)O(2)-1 were matrix-isolated and characterized by IR spectroscopy. The experimental IR spectra are in excellent agreement with results from DFT calculations. Irradiation of 1 with visible light produces the 2-oxepinoxy radical 5 in a clean reaction. Subsequent irradiation results in ring-opening and formation of several conformers of ketoketene 6. The radicals 1, 5, and 6 play an important role in the combustion of aromatic hydrocarbons and could now be isolated and spectroscopically characterized for the first time.