Enzyme catalytic nitration of aromatic compounds
Mingming Kong1, Kun Wang1, Runan Dong1
1School of Life Science, Beijing Institute of Technology, Beijing 100081, PR China.
Enzyme and Microbial Technology
|May 24, 2015
Summary
Enzyme catalysis offers a greener alternative for synthesizing nitroaromatic compounds. Horseradish peroxidase (HRP) in a non-aqueous system efficiently nitrates aromatic compounds, showing selectivity similar to traditional chemical methods.
Area of Science:
- Green Chemistry
- Enzyme Catalysis
- Organic Synthesis
Background:
- Nitroaromatic compounds are key synthetic intermediates.
- Traditional nitration methods use harsh chemicals, posing environmental concerns.
- Enzyme catalysis presents a sustainable alternative in chemical synthesis.
Purpose of the Study:
- To explore enzyme-catalyzed nitration of aromatic compounds using a non-aqueous horseradish peroxidase (HRP) system.
- To investigate the relationship between substrate structure, NBO charges, and nitro product distribution.
- To optimize reaction conditions for efficient and selective HRP-catalyzed nitration.
Main Methods:
- Utilized a non-aqueous horseradish peroxidase (HRP)/NaNO2/H2O2 reaction system.
- Investigated various reaction parameters including temperature, pH, and reactant concentrations.
- Employed density functional theory to calculate Natural Bond Orbital (NBO) charges on aromatic carbons.
- Analyzed substrate structural characteristics and nitro product distribution.
Main Results:
- Mild reaction conditions (ambient temperature, neutral pH) and controlled H2O2/NaNO2 concentrations prevented HRP inactivation and substrate polymerization.
- An aqueous-organic two-liquid phase system enhanced substrate solubility and reduced substrate inhibition compared to co-solvent systems.
- Substrates with NH2 or OH substituents showed high catalytic activity.
- Nitration preferentially occurred at ortho and para positions, mirroring chemical nitration selectivity.
Conclusions:
- The HRP/NaNO2/H2O2 system provides an effective and green method for aromatic nitration.
- Substrate structure, particularly electron-donating groups, and NBO charges dictate nitration site selectivity.
- This enzymatic approach offers a promising, environmentally friendly alternative to conventional nitration techniques.
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