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Accelerating effect of imidazolium ionic liquids on the singlet oxygen promoted oxidation of thioethers: A theoretical study

Paper ID Volume ID Publish Year Pages File Format Full-Text
27068 43998 2012 7 PDF Available
Title
Accelerating effect of imidazolium ionic liquids on the singlet oxygen promoted oxidation of thioethers: A theoretical study
Abstract

A computational study of the catalytic activity exhibited by imidazolium based ionic liquids on the singlet oxygen promoted oxidation of thioethers is presented. The reaction of singlet oxygen with thioanisole and diethyl sulfide, in the absence and in the presence of 1-butyl-3-methylimidazolium cation, was followed along the reaction coordinate up to the formation of the persulfoxide intermediate that is widely recognized as the key intermediate in this process. In line with previous experimental observations, the results obtained show that the imidazolium cation strongly stabilizes the persulfoxide intermediate by hydrogen bonding thus depressing the unproductive intersystem crossing and favoring product formation. Evidence for a significant role played by exciplex intermediates in this reaction was also found. Surprisingly, the results for the singlet oxygen-sulfide system in the absence of imidazolium show that whereas diethyl sulfide can readily form the persulfoxide intermediate, from which S-oxidation products ensue, for thioanisole the persulfoxide formation is characterized by a high activation energy. A detailed investigation on the role played by the aromatic ring in this dramatic activation energy increase is presented suggesting, for the first time, a rationale for the well known low reactivity exhibited by aromatic sulfides in reactions with singlet oxygen.

► We study theoretically the oxidation of thioethers by singlet oxygen with and without the effect of ionic liquids. ► We establish the reliability of DFT for study this kind of reaction. ► Reaction mechanisms for an aromatic and an aliphatic thioether. ► A rationale for different reactivity versus singlet oxygen of aromatic and aliphatic thioethers.

Keywords
Singlet oxygen; Thioethers; Density functional theory; Reaction mechanism; Oxidation
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Accelerating effect of imidazolium ionic liquids on the singlet oxygen promoted oxidation of thioethers: A theoretical study
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 240, 15 July 2012, Pages 59–65
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us