Acid-Catalyzed Electron Transfer Processes in Naphthalene peri-Dichalcogenides
Tyler A Tuck1, David J Press1, Brandon LeBlanc1
1Department of Chemistry , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada.
The Journal of Organic Chemistry
|August 28, 2018
Summary
Protonation of 1,8-naphthalene peri-dichalcogenides triggers single electron transfer (SET), forming radicals and causing NMR signal changes. This reversible proton-coupled electron transfer is enhanced by electron-donating substituents.
Area of Science:
- Organic Chemistry
- Supramolecular Chemistry
- Physical Chemistry
Background:
- 1,8-Naphthalene peri-dichalcogenides are electron-rich aromatic compounds.
- Protonation of such systems can lead to complex reaction pathways.
- Understanding electron transfer mechanisms is crucial in redox chemistry.
Purpose of the Study:
- To investigate the reaction mechanism of 1,8-naphthalene peri-dichalcogenides with Bronsted acids.
- To elucidate the role of single electron transfer (SET) in this process.
- To explore the influence of substituents on the electron transfer efficiency.
Main Methods:
- Protonation experiments using Bronsted acids (e.g., trifluoroacetic acid).
- Nuclear Magnetic Resonance (NMR) spectroscopy to observe signal changes.
- Electron Paramagnetic Resonance (EPR) spectroscopy and radical quenching studies (sodium dithionite).
- Computational chemistry methods.
Main Results:
- Protonation generates electrophilic cations, initiating single electron transfer (SET).
- Formation of radical species leads to significant NMR peak broadening and coalescence.
- The process is reversible upon treatment with base.
- 2,7-Dialkoxy substituents enhance electron transfer due to increased electron-donating ability.
Conclusions:
- The study demonstrates an unusual proton-coupled electron transfer (PCET) process in peri-dichalcogenides.
- Radical formation is a key intermediate in the reaction with strong acids.
- The findings offer insights into the redox behavior of electron-rich aromatic systems.
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