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UVA Self‐Photosensitized Oxygenation of β‐Ionone
Author(s) -
Borsarelli Claudio D.,
Mischne Mirta,
Venia Agustina La,
Vieyra Faustino E. Morán
Publication year - 2007
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2007.00147.x
Subject(s) - chemistry , photochemistry , singlet oxygen , quantum yield , flash photolysis , photodissociation , reaction rate constant , yield (engineering) , phosphorescence , propyne , excited state , oxygen , fluorescence , organic chemistry , materials science , kinetics , physics , quantum mechanics , nuclear physics , metallurgy
The steady‐state UVA (350 nm) photolysis of ( E )‐β‐ionone ( 1 ) in aerated toluene solutions was studied by 1 H NMR spectroscopy. The formation of the 1,2,4‐trioxane ( 2 ) and 5,8‐endoperoxide ( 5 ) derivatives in the ratio of 4:1 was observed. Time‐resolved laser induced experiments at 355 nm, such as laser‐flash photolysis, photoacoustic and singlet oxygen 1 O 2 phosphorescence detection, confirmed the formation of the excited triplet state of 1 with a quantum yield Φ T = 0.50 as the precursor for the generation of singlet oxygen 1 O 2 ( Φ Δ = 0.16) and the isomeric α‐pyran derivative ( 3 ), which was a reaction intermediate detected by NMR. In turn, the reaction of 1 O 2 with 1 and 3 occurred with rate constants of 1.0 × 10 6 and 2.5 × 10 8 m −1 s −1 to yield the oxygenated products 5 and 2 , respectively, indicating the relevance of the fixed s‐cis configuration in the α‐pyran ring in the concerted [2+4] cycloaddition of 1 O 2 .