Fluorobenzene

Fluorobenzene is an aryl fluoride and the simplest of the fluorobenzenes, with the formula C₆H₅F, often abbreviated PhF. A colorless liquid, it is a precursor to many fluorophenyl compounds.

Fluorobenzene

Structure of fluorobenzene Space-filling model of fluorobenzene
Names
Preferred IUPAC name Fluorobenzene
Other names Phenyl fluoride Monofluorobenzene
Identifiers
CAS Number	462-06-6 Y
3D model (JSmol)	Interactive image
Beilstein Reference	1236623
ChEBI	CHEBI:5115 Y
ChEMBL	ChEMBL16070 Y
ChemSpider	9614 Y
ECHA InfoCard	100.006.657
EC Number	207-321-7
Gmelin Reference	49856
KEGG	C11272 Y
PubChem CID	10008
UNII	G3TSZ68K12 Y
UN number	2387
CompTox Dashboard (EPA)	DTXSID4025329
InChI InChI=1S/C6H5F/c7-6-4-2-1-3-5-6/h1-5H Y Key: PYLWMHQQBFSUBP-UHFFFAOYSA-N Y InChI=1/C6H5F/c7-6-4-2-1-3-5-6/h1-5H Key: PYLWMHQQBFSUBP-UHFFFAOYAM
SMILES Fc1ccccc1
Properties
Chemical formula	C6H5F
Molar mass	96.103
Appearance	Colorless liquid
Density	1.025 g/mL, liquid
Melting point	−44 °C (−47 °F; 229 K)
Boiling point	84 to 85 °C (183 to 185 °F; 357 to 358 K)
Solubility in water	low
Magnetic susceptibility (χ)	−58.4·10−6 cm3/mol
Refractive index (nD)	1.46553
Structure
Molecular shape	Planar
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H225, H318, H411
Precautionary statements	P210, P233, P240, P241, P242, P243, P264, P273, P280, P303+P361+P353, P305+P351+P338, P310, P337+P313, P370+P378, P391, P403+P235, P501
NFPA 704 (fire diamond)	1 3 0
Related compounds
Related halobenzenes	Chlorobenzene Bromobenzene Iodobenzene
Related compounds	Benzene 1,2-Difluorobenzene
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Preparation

PhF was first reported in 1886 by O. Wallach at the University of Bonn, who prepared the compound in two steps. Phenyldiazonium chloride was first converted to a triazene using piperidine:

[PhN₂]Cl + 2 (CH₂)₅NH → PhN=N-N(CH₂)₅ + [(CH₂)₅NH₂]Cl

The triazine was then cleaved with hydrofluoric acid:

PhN=N-N(CH₂)₅ + 2 HF → PhF + N₂ + [(CH₂)₅NH₂]F

Historical note: in Wallach's era, the element fluorine was symbolized with "Fl". Thus, his procedure is subtitled "Fluorbenzol, C₆H₅Fl".^[1]

On the laboratory scale, PhF is prepared by the thermal decomposition of the benzenediazonium tetrafluoroborate:

PhN₂BF₄ → PhF + BF₃ + N₂

According to the procedure, solid [PhN₂]BF₄ is heated with a flame to initiate an exothermic reaction, which also affords boron trifluoride and nitrogen gas. Product PhF and BF₃ are readily separated because of their differing boiling points.^[2]

The technical synthesis is by the reaction of cyclopentadiene with difluorocarbene. The initially formed cyclopropane undergoes a ring expansion and subsequent elimination of hydrogen fluoride.

Reactions

PhF behaves rather differently from other halobenzene derivatives owing to the pi-donor properties of fluoride. For example, the para position is more activated than benzene toward electrophiles. For this reason, it can be converted to 1-bromo-4-fluorobenzene with relatively high efficiency.^[3]

Solvent properties

Structure of [(C₅Me₅)₂Ti(FC₆H₅)]⁺, a coordination complex of fluorobenzene.

PhF is a useful solvent for highly reactive species. Its melting point at −44 °C is lower than that of benzene. In contrast, the boiling points of PhF and benzene are very similar, differing by only 4 °C. It is considerably more polar than benzene, with a dielectric constant of 5.42 compared to 2.28 for benzene at 298 K.^[4] Fluorobenzene is a relatively inert compound reflecting the strength of the C–F bond.

Although it is usually considered a non-coordinating solvent, a metal complex of PhF has been crystallized.^[5]

See also

• Bromobenzene
• Chlorobenzene
• Iodobenzene
• Pentafluoromethylbenzene