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Updated: Jun 8, 2026

Reliable Mechanochemistry: Protocols for Reproducible Outcomes of Neat and Liquid Assisted Ball-mill Grinding Experiments
Published on: January 23, 2018
Switchable selectivity during oxidation of anilines in a ball mill
Rico Thorwirth1, Franziska Bernhardt, Achim Stolle
1Institute for Technical Chemistry and Environmental Chemistry, Friedrich-Schiller University Jena, Lessingstraße 12, 07743 Jena, Germany.
A novel solvent-free planetary ball mill method oxidizes anilines to azo, azoxy, or nitro compounds. Selectivity is controllable by oxidant and auxiliary choice, offering an energy-efficient alternative.
Area of Science:
- Green Chemistry
- Organic Synthesis
- Mechanochemistry
Background:
- Direct oxidation of anilines is crucial for synthesizing azo and azoxy compounds.
- Traditional methods often require solvents and harsh conditions, posing environmental concerns.
- Developing solvent-free, energy-efficient synthetic routes is a key goal in sustainable chemistry.
Purpose of the Study:
- To develop a solvent-free mechanochemical method for direct aniline oxidation.
- To achieve selective synthesis of azo, azoxy, and nitro compounds from anilines.
- To evaluate the energy efficiency and advantages of the ball mill approach compared to other energy inputs.
Main Methods:
- Utilized a planetary ball mill for solvent-free direct oxidation of anilines.
- Investigated various oxidants and grinding auxiliaries to optimize reaction conditions.
- Explored a range of substituted aromatic anilines to assess substrate scope.
- Compared the ball mill method with microwave, classical heating, and ultrasound energy inputs.
Main Results:
- Successfully synthesized azo, azoxy, and nitro compounds from aromatic anilines.
- Demonstrated chemoselective control over product formation (azo, azoxy, or nitro).
- Showcased switchable selectivity by varying the combination of oxidant and grinding auxiliary.
- Highlighted the high energy efficiency of the planetary ball mill method.
Conclusions:
- A versatile and solvent-free mechanochemical method for aniline oxidation was established.
- The reaction offers tunable selectivity for azo, azoxy, or nitro product formation.
- Planetary ball milling presents a highly energy-efficient and environmentally friendly alternative to conventional heating methods for aniline oxidation.
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