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NHPI Stephenson.pdf (2.07 MB)

On the Mechanism of Electrochemical Generation and Decomposition of Phthalimide N-oxyl (PINO)

preprint
submitted on 14.04.2021, 01:57 and posted on 15.04.2021, 08:20 by Cheng Yang, Luke Farmer, Derek Pratt, Stephen Maldonado, Corey Stephenson
Phthalimide N-oxyl (PINO) is a potent hydrogen atom transfer (HAT) catalyst that can be generated electrochemically from N-hydroxyphthalimide (NHPI). However, catalyst decomposition has limited its application. This paper details mechanistic studies of the generation and decomposition of PINO under electrochemical conditions. Voltammetric data, observations from bulk electrolysis, and computational studies suggest two primary aspects. First, base-promoted formation of PINO from NHPI occurs via multiple-site concerted proton-electron transfer (MS-CPET). Second, PINO decomposition occurs by at least two second-order paths, one of which is greatly enhanced by base. Optimal catalytic efficiency in PINO-catalyzed oxidations occurs in the presence of bases whose corresponding conjugate acids have pKas in the range of 12-15, which strike a balance between promoting PINO formation and minimizing its decay.

Funding

ECO-CBET: Electrodeless Electrochemical Valorization of Lignin

Directorate for Engineering

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SusChEM: Catalytic lignin degradation

Directorate for Mathematical & Physical Sciences

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Light-Stimulated Hole Injection at Chemically Modified Photocathodes: Development of Semiconductor Ultramicroelectrodes for Measurement of Heterogeneous Charge Transfer

Basic Energy Sciences

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History

Email Address of Submitting Author

crjsteph@umich.edu

Institution

University of Michigan

Country

USA

ORCID For Submitting Author

0000-0002-2443-5514

Declaration of Conflict of Interest

None

Exports

ChemRxiv

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