1. In Search of Aryloxenium Ions
Michael Novak
Department of Chemistry and Biochemistry
Miami University
Laser flash photolysis of 4-acetoxy-4-(4´-methylpheny)-2,5-cyclohexadienone (2b) in water generates two transient absorbance bands (A). The one with λmax 460 nm decays in a first-order manner with a lifetime of 170 ns that is independent of O2, but decreases with increasing [N3-]. The intermediate associated with that band is identified as 1b based on the sensitivity to N3- and the agreement between its calculated (B3LYP/6-31G(d)) and observed time resolved resonance Raman (TR3) spectrum. In CH3CN only the shorter wavelength band is observed (B). This band decays in a biphasic manner on the μs time scale, and is only slightly sensitive to O2. The intermediate associated with this band is identified as the radical 5b based on identification of reaction products, comparison of the uv spectrum to the authentic biphenylyloxy radical, and on kinetic modeling of the decay kinetics.