Photochemistry of dipenylketyl radicals: spectroscopy, kinetics, and mechanisms
The photochemistry of the diphenylketyl radical has been examined in nonpolar solutions. Transient studies using two-laser techniques yield an excited-state lifetime of 3.9 ns in toluene at room temperature, while for diphenylketyl-O-d the lifetime is 8.7 ns. Dye laser irradiation (515 nm) in the ketyl's visible absorption band leads to efficient photobleaching with Phi/sub bleach/ = 0.27 +/- 0.06 for the parent radical and 0.39 and 0.26 for the 4-methyl and 4-chloro derivatives, respectively. The photobleaching reaction involves the cleavage of the O-H ketyl bond to yield benzophenone and hydrogen atoms; in cyclohexane the latter abstract hydrogen from the solvent to produce molecular hydrogen which was characterized by Raman spectroscopy. In accordance with this mechanism, two-laser experiments produce lower yields of photoreduction products than the one-laser experiments in which the ketyls are not photobleached. When the ketyl radicals are generated by reaction of tert-butoxy radicals with benzhydrol, dye laser irradiation leads to a large increase in the yield of benzophenone (now a product), although the mechanism here is somewhat more complex due to the quenching of excited ketyl radicals by di-tert-butyl peroxide (k/sub q/ = 1.9 x 10/sup 9/ M/sup -1/ s/sup -1/). Detailed studies of the fluorescence, isotope effects, temperature effects, and products are also included.
- Research Organization:
- National Research Council or Canada, Ottawa, Ontario
- OSTI ID:
- 5413357
- Journal Information:
- J. Am. Chem. Soc.; (United States), Vol. 110:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
PHENYL RADICALS
EXCITED STATES
FLUORESCENCE
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
ARRHENIUS EQUATION
CHEMICAL REACTION KINETICS
EXPERIMENTAL DATA
ISOTOPE EFFECTS
LASERS
LIFETIME
MEDIUM TEMPERATURE
RAMAN SPECTROSCOPY
SOLUTIONS
TEMPERATURE DEPENDENCE
TOLUENE
ALKYLATED AROMATICS
AROMATICS
ARYL RADICALS
CHEMICAL REACTIONS
CHEMISTRY
DATA
DISPERSIONS
ENERGY LEVELS
EQUATIONS
HYDROCARBONS
INFORMATION
KINETICS
LASER SPECTROSCOPY
LUMINESCENCE
MIXTURES
NUMERICAL DATA
ORGANIC COMPOUNDS
RADICALS
REACTION KINETICS
SPECTROSCOPY
400500* - Photochemistry