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Ultrasonic chemical oxidative degradations of 1,3-dialkylimidazolium ionic liquids and their mechanistic elucidations

Li, X.H., Zhao, J.G., Li, Q.H., Wang, L.F. and Tsang, S.C. (2007) Ultrasonic chemical oxidative degradations of 1,3-dialkylimidazolium ionic liquids and their mechanistic elucidations. Dalton Transactions (19). pp. 1875-1880. ISSN 1364-5447

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To link to this item DOI: 10.1039/b618384k

Abstract/Summary

A highly efficient process for oxidative degradation of 1,3-dialkylimidazolium ionic liquids in hydrogen peroxide/acetic acid aqueous medium assisted by ultrasonic chemical irradiation is, for the first time, described. It is shown that more than 93% of the 1,3-dialkylimidazolium cation with the corresponding Cl-, Br-, BF4- and PF6- counter-anions at a concentration of 2.5 mM can be degraded at 50 degrees C within 12 h while at 72 h the conversions approach 99%. A tentative mechanism for the degradation of these ILs is for the first time proposed through a detailed kinetic analysis of several characteristic transients and/or immediate products, which are identified during the ILs degradation using GC-MS. The results clearly indicate that three hydrogen atoms in the imidazolium ring are the first sites preferably oxidized, followed by cleavage of the alkyl groups attached to the N atoms from the ring. The nature of the alkyl chain length on the imidazolium ring and the type of counter anion do not seem to affect the degradation process. Further, selective fragmentations of C-N bonds of the imidazolium or derived ring lead to ring opening, forming degraded intermediates. It is also shown that acetoxyacetic acid and biurea are the final kinetically stable degraded products from the ILs under the degradation conditions.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
ID Code:11428
Uncontrolled Keywords:1-N-BUTYL-3-METHYLIMIDAZOLIUM HEXAFLUOROPHOSPHATE, PHOTOSENSITIZED, OXIDATION, COUPLING REACTIONS, MOLTEN-SALTS, FORCE-FIELD, TEMPERATURE, IMIDAZOLIUM, TOXICITY, DERIVATIVES, CATALYSIS
Publisher:Royal Society of Chemistry

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