High-Temperature Reactions of Hexafluorobenzene

Area of Science:

• Organic Chemistry
• Fluorine Chemistry

Background:

• Aromatic fluorine substitution traditionally requires nucleophilic reagents.
• Hexafluorobenzene (C6F6) is a key fluorinated aromatic compound.

Purpose of the Study:

• To explore non-nucleophilic substitution of aromatic fluorine in hexafluorobenzene.
• To achieve fluorine replacement using weakly nucleophilic or non-nucleophilic reagents at high temperatures.

Main Methods:

• Reactions of hexafluorobenzene with non-nucleophilic reagents (e.g., Br2, Cl2, tetrafluoroethylene) at 300-850 °C.
• Passage of hexafluorobenzene over alkali or alkaline earth-metal halides at elevated temperatures.

Main Results:

• Successful replacement of nuclear fluorine in hexafluorobenzene by non-nucleophilic reagents.
• Formation of bromopentafluorobenzene, chloropentafluorobenzene, and octafluorotoluene as major products.
• Synthesis of pentafluorohalobenzenes via reaction with metal halides.

Conclusions:

• High-temperature reactions provide a new route for aromatic fluorine substitution.
• Pyrolytic reactions likely involve free-radical intermediates.
• Ionic or complex free radical-ionic mechanisms may operate with ionic coreactants.