1,2-Difluorobenzene, also known as DFB, is an aromatic compound with formula C6H4F2. This colorless flammable liquid is a solvent used in the electrochemical studies of transition metal complexes. Compared to most conventional halogenated aliphatic and aromatic solvents, it possesses an exceptionally high dielectric constant (ε0 = 13.8 at 300 K). Thus, it can be a suitable solvent for cationic, and/or highly electrophilic organometallic complexes.
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Synthesis
Difluorobenzenes can be prepared by the Balz-Schiemann reaction, which entails conversion of diazonium tetrafluoroborate salts to their fluorides. The synthesis of 1,2-difluorobenzene starts with 2-fluoroaniline:
C6H4F(NH2) + HNO2 + HBF4 → [C6H4F(N2)]BF4 + 2 H2O
[C6H4F(N2)]BF4 → C6H4F2 + N2 + BF3
The syntheses of 1,3- and 1,4-difluorobenzene proceed respectively from 1,3- and 1,4-diaminobenzene, which are doubly diazotized.
Laboratory applications
Organometallic derivatives of 1,2-difluorobenzene have been well developed. It is found to be a weaker base than benzene.
1,2-Difluorobenzene has been used as solvent for the electrochemical analysis of transition metal complexes. It is relatively chemically inert, weakly coordinating and has a relatively high dielectric constant. In contrast to acetonitrile, DMSO, and DMF it is a weakly coordinating solvent for metal complexes, .
It has anaesthetic properties.
1,2-Difluorobenzene can be acylated to 3',4'-difluoropropiophenone.