Nanosecond transient processes in the triethylamine quenching of benzophenone triplets in aqueous alkaline media. Substituent effect, ketyl radical deprotonation, and secondary photoreduction kinetics

Journal Article · Thu Aug 14 04:00:00 EDT 1986 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100408a032· OSTI ID:5469570

Bhattacharyya, K; Das, P K

In the course of benzophenone triplet quenching by triethylamine (TEA) at high concentrations in alkaline aqueous acetonitrile, two temporally distinct processes are observed for ketyl radical anion formation. The fast component occurs on a nanosecond time scale, has kinetics sensitive to basicity and water content of the medium, and is ascribed to the deprotonation of the diphenylhydroxymethyl radical initially produced as a result of subnanosecond intra-ion-pair proton transfer. The slow process occurs on a microsecond time scale and is characterized by pseudo-first-order rate constants linearly dependent on ketone ground-state concentration; this is assigned to the one-electron reduction of the ketone by the methyl(diethylamino)methyl radical (derived from TEA). Substituent effects on the kinetics of the two processes follow trends expected from those of the acidity of diarylhydroxymethyl radicals and of the behavior of diaryl ketones as oxidants. Neither of the two processes is observed with N,N-dimethylaniline (DMA) and 1,4-diazabicyclo(2.2.2)octane (DABCO) as quenchers. The electron or hydrogen transfer yields in the course of diaryl ketone triplet quenching by the three amines are all close to unity, suggesting that the back electron transfer in the triplet ion pairs is relatively unimportant.

• Research Organization: Univ. of Notre Dame, IN
• OSTI ID: 5469570
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 90:17; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ACETONITRILE
AMINES
ANIONS
BENZOPHENONE
CHARGED PARTICLES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DATA
DE-EXCITATION
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXPERIMENTAL DATA
GAS DYNAMIC LASERS
GAS LASERS
HYDROGEN TRANSFER
INFORMATION
IONS
KETONES
KINETICS
LASERS
NITRILES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
RADIATIONLESS DECAY
REACTION INTERMEDIATES
REACTION KINETICS
TIME DEPENDENCE