Ionic Liquid Stabilized 2,2,6,6-Tetramethylpiperidine 1‑Oxyl Catalysis for Alcohol Oxidation

N-Oxyl reagents, particularly 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), have been extensively used for alcohol oxidations. While TEMPO-mediated oxidations are kinetically and thermodynamically favorable in high-pH electrolytes, base-induced degradation often results in significant loss of cataly...

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Bibliographic Details
Published in:ACS sustainable chemistry & engineering 2020-03, Vol.8 (11), p.4489-4498
Main Authors: Li, Min, Klunder, Kevin, Blumenthal, Emmy, Prater, Matthew B, Lee, Jack, Matthiesen, John E, Minteer, Shelley D
Format: Article
Language:English
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Summary:N-Oxyl reagents, particularly 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), have been extensively used for alcohol oxidations. While TEMPO-mediated oxidations are kinetically and thermodynamically favorable in high-pH electrolytes, base-induced degradation often results in significant loss of catalytic activity. Herein, we demonstrate enhanced alkaline stability of a TEMPO derivative in ionic liquids (ILs). By incorporating TEMPO in an imidazole-anchored IL, no loss of current was observed at pH 10.0 after 2.0 h during the oxidation of butanol and glycerol, while TEMPO in polycaprolactone (PCL), a patternable binder material, degraded 58.5% and 67.1%, respectively. The stability enhancement was further demonstrated by analyzing the conversion of glycerol in an 800 μL electrochemical cell using bulk chemical analysis techniques. Successive cycles of glycerol oxidation indicated 14-fold stability enhancement by applying IL in a TEMPO electrode composite in comparison to PCL. The strategy demonstrated here provides an opportunity to prepare catalytic systems with enhanced stability. Further, this method provides the ability to convert what are typically homogeneous catalysts to heterogeneous systems.
ISSN:2168-0485
2168-0485
DOI:10.1021/acssuschemeng.9b07650