Magnetic and micellar effects on photoreactions. Micellar cage and magnetic isotope effects on quantum yields. Correlation of /sup 13/C enrichment parameters with quantum yield measurements
The photoinduced homolytic ..cap alpha..-cleavage reaction of dibenzyl ketone (DBK) produces a germinate triplet radical pair whose reactivity has been shown to be significantly influenced by micellar and magnetic effects (included in Scheme). The products derived from the initial PhCH/sub 2/COCH/sub 2/Ph triplet radical pair (/sup 3/D) may be classified as germinate (spin-correlated) products which form in a cage process or as free-radical (spin-uncorrelated) products which form after diffusional separation of the initially formed radical pair. The remarkable /sup 13/C enrichment discovered in recovered DBK after partial photolysis in micellar solution was interpreted in terms of an enhanced cage effect of radical pairs in a micellar and a magnetic isotope (/sup 13/C) effect. The enhanced cage effects of radical pairs in micelles predict (1) a decreased quantum yield for disappearance of DBK and appearance of 1,2-diphenylethane (DPE) in hexadecyltrimethylammonium chloride (HDTCl) micelles relative to the quantum yields in homogeneous benzene solution. The magnetic isotope effect concept allows these predictions: (2) the quantum yield for disappearance of DBK and appearance of DPE will be significantly less for a ketone enriched in /sup 13/C in the carbonyl carbon; (3) the quantum yield for disappearance of DBK and appearance of DPE will be influenced by the application of an external laboratory magnetic field on the sample during photolysis; (4) the quantum yields for cage reactions will be magnetic field dependent; (5) the magnitude of ..cap alpha.., predicted by Bernstein's formula is directly related to the value of ..cap alpha.. derived from quantum yield measurements. All five predictions were confirmed. 1 table. (DP)
- Research Organization:
- Columbia Univ., New York, NY
- OSTI ID:
- 5528521
- Journal Information:
- J. Am. Chem. Soc.; (United States), Vol. 101:24
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBON 13
ISOTOPE EFFECTS
KETONES
PHOTOLYSIS
BENZENE
CARBONYLS
MAGNETIC FIELDS
MICELLAR SYSTEMS
PAIR PRODUCTION
QUANTUM MECHANICS
RADICALS
AROMATICS
CARBON ISOTOPES
CHEMICAL REACTIONS
DECOMPOSITION
EVEN-ODD NUCLEI
HYDROCARBONS
INTERACTIONS
ISOTOPES
LIGHT NUCLEI
MECHANICS
NUCLEI
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
STABLE ISOTOPES
400302* - Organic Chemistry- Isotope Effects- (-1987)
400500 - Photochemistry