Photochemistry of dipenylketyl radicals: spectroscopy, kinetics, and mechanisms

Journal Article · Wed Jan 20 04:00:00 EST 1988 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00210a035· OSTI ID:5413357

Johnston, L J; Lougnot, D J; Wintgens, V; Scaiano, J C

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), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 110:2; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ALKYLATED AROMATICS
AROMATICS
ARRHENIUS EQUATION
ARYL RADICALS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
DATA
DISPERSIONS
ENERGY LEVELS
EQUATIONS
EXCITED STATES
EXPERIMENTAL DATA
FLUORESCENCE
HYDROCARBONS
INFORMATION
ISOTOPE EFFECTS
KINETICS
LASER SPECTROSCOPY
LASERS
LIFETIME
LUMINESCENCE
MEDIUM TEMPERATURE
MIXTURES
NUMERICAL DATA
ORGANIC COMPOUNDS
PHENYL RADICALS
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
RADICALS
RAMAN SPECTROSCOPY
REACTION KINETICS
SOLUTIONS
SPECTROSCOPY
TEMPERATURE DEPENDENCE
TOLUENE