Electrochemical Activation of C−C Bonds through Mediated Hydrogen Atom Transfer Reactions
Abstract
Activating inert sp3 -sp3 carbon-carbon (C-C) bonds remains a major bottleneck in the chemical upcycling of recalcitrant polyolefin waste. In this study, redox mediators are used to activate the inert C-C bonds. Specifically, N-hydroxyphthalimide (NHPI) is used as the redox mediator, which is oxidized to phthalimide-N-oxyl (PINO) radical to initiate hydrogen atom transfer (HAT) reactions with benzylic C-H bonds. The resulting carbon radical is readily captured by molecular oxygen to form a peroxide that decomposes into oxygenated C-C bond-scission fragments. This indirect approach reduces the oxidation potential by >1.2 V compared to the direct oxidation of the substrate. Studies with model compounds reveal that the selectivity of C-C bond cleavage increases with decreasing C-C bond dissociation energy. With NHPI-mediated oxidation, oligomeric styrene (OS510 ; Mn =510 Da) and polystyrene (PS; Mn ≈10 000 Da) are converted into oxygenated monomers, dimers, and oligomers.
We thank Griffin Drake, Thejas Wesley, Dr. Julie Rorrer, Dr. Ydna Questell‐Santiago, and other members of the BOTTLE Consortium for helpful discussions. Funding was provided by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office (AMO) and Bioenergy Technologies Office (BETO). This work was performed as part of the BioOptimized Technologies to keep Thermoplastics out of Landfills and the Environment (BOTTLE) Consortium and was supported by AMO and BETO under Contract DE‐AC36‐08GO28308 with the National Renewable Energy Laboratory (NREL), operated by Alliance for Sustainable Energy, LLC. The BOTTLE Consortium includes members from MIT and Colorado State University, funded under Contract DE‐AC36‐08GO28308 with NREL. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. This work was also supported by Eni S.p.A. through the MIT Energy Initiative.
