Fluorobenzene

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Fluorobenzene
Structure of fluorobenzene
Structure of fluorobenzene
Space-filling model of fluorobenzene
Space-filling model of fluorobenzene
Names
Preferred IUPAC name
Fluorobenzene
Other names
Phenyl fluoride
Monofluorobenzene
Identifiers
3D model (
JSmol
)
1236623
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard
 100.006.657 Edit this at Wikidata
EC Number
  • 207-321-7
49856
KEGG
UNII
UN number 2387
  • InChI=1S/C6H5F/c7-6-4-2-1-3-5-6/h1-5H checkY
    Key: PYLWMHQQBFSUBP-UHFFFAOYSA-N checkY
  • InChI=1/C6H5F/c7-6-4-2-1-3-5-6/h1-5H
    Key: PYLWMHQQBFSUBP-UHFFFAOYAM
  • Fc1ccccc1
Properties
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)
low
-58.4·10−6 cm3/mol
1.46553
Structure
Planar
Hazards
GHS labelling:
GHS02: FlammableGHS05: CorrosiveGHS07: Exclamation mark
Warning
H225, H318, H411
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)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
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).
checkY verify (what is checkY☒N ?)

Fluorobenzene is an

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

Preparation

PhF was first reported in 1886 by O. Wallach at the

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

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

References

  1. doi:10.1002/jlac.18862350303
  2. doi:10.15227/orgsyn.013.0046
    ..
  3. doi:10.1021/ed080p679
    .
  4. ^ Table of Dielectric Constants of Pure Liquids. National Bureau of Standards. 1951.
  5. doi:10.1016/B0-08-045047-4/00028-5
    .
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