| Autor: |
Borsarelli, Claudio D., Mischne, Mirta, Venia, Agustina La, Vieyra, Faustino E. Morán |
| Předmět: |
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| Zdroj: |
Photochemistry & Photobiology; Nov/Dec2007, Vol. 83 Issue 6, p1313-1318, 6p, 2 Diagrams, 5 Graphs |
| Abstrakt: |
The steady-state UVA (350 nm) photolysis of ( E)-β-ionone ( 1) in aerated toluene solutions was studied by 1H 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 1O2 phosphorescence detection, confirmed the formation of the excited triplet state of 1 with a quantum yield ΦT = 0.50 as the precursor for the generation of singlet oxygen 1O2 ( ΦΔ = 0.16) and the isomeric α-pyran derivative ( 3), which was a reaction intermediate detected by NMR. In turn, the reaction of 1O2 with 1 and 3 occurred with rate constants of 1.0 × 106 and 2.5 × 108 m−1s−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 1O2. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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