Tuning Green Explosives through S_NAr Chemistry.

Area of Science:

• Organic Chemistry
• Materials Science

Background:

• Nucleophilic aromatic substitution (S_NAr) reactions are fundamental in organic synthesis.
• Polyfluorinated aromatic compounds offer unique reactivity profiles.
• Azido-substituted compounds are precursors to energetic materials.

Purpose of the Study:

• To investigate the reactivity and regioselectivity of S_NAr fluorine substitution with azide in polyfluorinated nitrobenzenes.
• To characterize the resulting polyazido-substituted nitrobenzene derivatives.
• To study the thermal decomposition and energetic properties of these compounds.

Main Methods:

• Theoretical calculations using Density Functional Theory (DFT).
• Experimental characterization including Nuclear Magnetic Resonance (NMR), Infrared (IR) spectroscopy, High-Performance Liquid Chromatography (HPLC), and X-ray crystallography.
• Thermal decomposition studies (controlled kinetic decay and uncontrolled explosion modes).

Main Results:

• Azide substitution preferentially occurred at the para- and ortho-positions relative to the nitro group.
• Transazidation reactions were observed.
• Controlled thermal decomposition of ortho-azidonitrobenzenes yielded benzofuroxans, except when an adjacent azido group was present.
• The bursting power of azidonitrobenzenes increased with the number of azide substituents.

Conclusions:

• The regioselectivity of azide substitution is governed by the nitro group's electronic influence.
• Polyazido-substituted nitrobenzenes exhibit tunable energetic properties.
• Benzofuroxan formation is a key decomposition pathway for ortho-azidonitrobenzenes.