Is Electron Transfer a Step in the Nitration of Reactive Aromatics?
1Department of Chemistry, University of California─San Diego, La Jolla, California 92093-0358, United States.
The Journal of Organic Chemistry
|February 17, 2026
Summary
Electrochemical synthesis and direct nitration of naphthalene yield similar nitronaphthalene ratios, suggesting a shared radical pair mechanism in both processes. This mechanism explains nitration selectivity.
Area of Science:
- Organic Chemistry
- Electrochemistry
- Reaction Mechanisms
Background:
- Naphthalene nitration typically employs mixed acids (HNO3 + H2SO4).
- Electrochemical methods offer alternative synthetic routes for aromatic functionalization.
- Understanding reaction intermediates is crucial for controlling selectivity.
Purpose of the Study:
- To investigate the mechanism of naphthalene nitration using controlled-potential electrolysis.
- To compare the product distribution from electrochemical nitration with direct nitration.
- To provide evidence for a radical pair mechanism in naphthalene nitration.
Main Methods:
- Controlled-potential electrolysis of naphthalene in the presence of NO2.
- Analysis of nitronaphthalene isomer ratios using chromatography.
- Comparison of electrochemical results with literature data for direct nitration.
Main Results:
- Electrolysis produced a nitronaphthalene mixture with a 1-nitronaphthalene to 2-nitronaphthalene ratio of 10.2 ± 1.
- This ratio closely matched the 10.9 ± 1 obtained from direct nitration.
- The similar product distribution suggests a common intermediate in both methods.
Conclusions:
- The formation of a radical pair is proposed as a unifying mechanism for both electrochemical and direct naphthalene nitration.
- This radical pair mechanism explains the observed high intramolecular selectivity.
- The study supports the hypothesis that electron transfer precedes C-N bond formation in direct nitration.
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