Photoaddition and photoreduction of chloranil with arenes via singlet and triplet excited complexes: effects of irradiation wavelength and radical ion pair spin multiplicity

Journal Article · Wed Mar 16 04:00:00 EST 1988 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00214a043· OSTI ID:7255993

Jones, G II; Haney, W A; Phan, X T

The photochemistry of chloranil (Q) in the presence of the arenes hexamethylbenzene, 1-methyl-, 1,3-dimethyl-, 1,4-dimethyl-, and 2,3-dimethylnaphthalene, and acenaphthene has been investigated. Irradiation in a nonpolar solvent provided ether adducts resulting from formal addition of the quinone to the arene side chain, the hydroquinone, (QH/sub 2/), and in one case, an identifiable oxidation product, acenaphthylene. The quantum yield for these transformations was shown to have a complex dependence on the concentration of the arene and irradiation wavelength. On irradiation at 366 nm under conditions in which free chloranil absorbs, the preferred product was the reduced species, QH/sub 2/. On irradiation at 436 nm under conditions in which the ground-state charge-transfer (CT) complex of Q and the arene chiefly absorbs, the preferred product was the ether adduct. Excitation of complexes at 546 nm resulted in a sharply reduced quantum yield. Flash photolysis studies show that the quenching of Q triplets by the arenes leads to free radicals (QH/sup ./ and DH/sup ./) by a sequential electron-transfer, proton-transfer mechanism. Irradiation of QDH/sub 2/ complexes appears alternatively to lead to singlet radical ion pairs (Q/sup .-/, DH/sub 2//sup .+/) which evolve into singlet radical pairs (QH/sup ./, DH/sup ./) and final products in competition with back reactions which return radical pairs to ground-state reactants.

• Research Organization: Boston Univ., MA (USA)
• OSTI ID: 7255993
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 110:6; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ABSORPTION SPECTROSCOPY
AROMATICS
BENZOQUINONES
CHEMICAL REACTIONS
CHEMISTRY
CHLORANIL
DATA
EFFICIENCY
ENERGY LEVELS
EXCITED STATES
EXPERIMENTAL DATA
INFORMATION
MULTIPLETS
NUMERICAL DATA
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
QUANTUM EFFICIENCY
QUINONES
RADICALS
REDUCTION
SPECTROSCOPY
TRIPLETS