ORGN 85 |
| We previously proposed a unimolecular photochemical mechanism for dibenzothiophene-S-oxide (DBTO) and dibenzoselenophene-Se-oxide (DBSeO) photodeoxygenation, in which formation of O(3P) accompanies the sulfide or selenide product. Sensitized photodeoxygenation of DBTO and DBSeO was investigated to gain further insight on the mechanism. By use of trapping studies, observed product ratios, or “fingerprints”, should indirectly indicate the presence or absence of a common oxidizing intermediate. The energetics of the DBTO and DBSeO systems differ in that the S-O bond strength of DBTO exceeds the spectroscopic triplet, while estimates for the Se-O bond strength and DBSeO triplet energy are more comparable. Therefore, it may be possible for unimolecular cleavage of the Se-O bond to occur out of the triplet, but is unlikely for the sulfoxide analogue. Different oxidation fingerprints are observed under direct and sensitized irradiations of DBTO, indicating different mechanisms. Results for sensitized photolysis of DBSeO suggest the possibility of competitive deoxygenation mechanisms.
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Physical Organic Chemistry: Calculations, Mechanisms, Photochemistry, and High-Energy Species
1:00 PM-5:20 PM, Sunday, 10 September 2006 Moscone Center -- Room 133, Oral
Division of Organic Chemistry |
