Redox catalysis involving substrate photooxidation with catalyst regeneration by substrate reduction. Simultaneous oxidative C-H bond cleavage and reductive C-S bond cleavage in thioethers catalyzed by W sub 10 O sub 32 sup 4 minus
- Emory Univ., Atlanta, GA (United States)
Several experiments examining the photooxidation of thioethers by polyoxotungstates have established that the less oxidizing photochemically active complex W{sub 10}O{sub 32}{sup 4{minus}} but not the more oxidizing photochemically active heteropolytungstates such as {alpha}-PW{sub 12}O{sub 40}{sup 3{minus}} can be used to effect both substrate photooxidation and reduction in the same reaction. Under anaerobic conditions in solution at ambient temperature, the excited state of W{sub 10}O{sub 32}{sup 4{minus}} reacts with thioethers in high selectivity by {alpha}-hydrogen abstraction to form the {alpha}-carbon radicals. Neither photooxidation by electron transfer to generate the thioether cation radicals nor production of the conventional oxygenated products, sulfoxide and sulfone, is seen in these reactions. The principal reduced form of the catalyst, W{sub 10}O{sub 32}{sup 6{minus}}, reduces thioethers to effect C-S bond cleavage; thus, the net observed products in anaerobic photooxidation of these substrates catalyzed by W{sub 10}O{sub 32}{sup 4{minus}} are the dimers resulting from coupling of the {alpha}-carbon radicals and C-S bond cleavage products including the hydrocarbon resulting from complete desulfurization of the thioether. The only important processes exhibited by the excited state,W{sub 10}O{sub 32}{sup 4{minus}*}, under conditions where background photooxidation of CH{sub 3}CN solvent is not significant ((thioether) > 25 mM) are attack on thioether substrate, k, and unimolecular radiationless decay, k{sub rd}.
- OSTI ID:
- 5542815
- Journal Information:
- Journal of the American Chemical Society; (United States), Vol. 112:23; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
SULFIDES
PHOTOCHEMICAL REACTIONS
TUNGSTEN OXIDES
CATALYTIC EFFECTS
ABSORPTION SPECTROSCOPY
ANAEROBIC CONDITIONS
CATALYSIS
CHEMICAL BONDS
CHEMICAL REACTION KINETICS
EXCITED STATES
EXPERIMENTAL DATA
GAS CHROMATOGRAPHY
IONS
LIQUID COLUMN CHROMATOGRAPHY
RADICALS
REDOX REACTIONS
REDUCTION
SAMPLE PREPARATION
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL REACTIONS
CHROMATOGRAPHY
DATA
ENERGY LEVELS
INFORMATION
KINETICS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
REFRACTORY METAL COMPOUNDS
SEPARATION PROCESSES
SPECTROSCOPY
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TUNGSTEN COMPOUNDS
400500* - Photochemistry
400201 - Chemical & Physicochemical Properties