Fluorobenzene

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Fluorobenzene
Structure of fluorobenzene
Space-filling model of fluorobenzene
Names
IUPAC name
Fluorobenzene
Other names
Phenyl fluoride
Monofluorobenzene
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.006.657
KEGG
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
Structure
Planar
Hazards
R-phrases (outdated) R36, R37, R38
S-phrases (outdated) S16, S26, S36
NFPA 704
Flammability code 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. gasolineHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
3
1
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 ☑Y☒N ?)
Infobox references

Fluorobenzene is the chemical compound with the formula C6H5F, often abbreviated PhF. This species is a derivative of benzene, with a single fluorine atom attached.

Properties[edit]

Its melting point is -44 °C, which is lower than that of benzene, as a result of the reduced symmetry of the molecule compared to 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.[1]

Preparation[edit]

On the laboratory scale, PhF is conveniently prepared by the thermal decomposition of the benzenediazonium tetrafluoroborate[2]

PhN2BF4 → PhF + BF3 + N2

According to the procedure, solid [PhN2]BF4 is heated with a flame to initiate an exothermic reaction that affords two volatile products, PhF and BF3, which are readily separated because of their differing boiling points.

History[edit]

PhF was first reported in 1886 by O. Wallach at the University of Bonn, who prepared the compound in two steps, starting also with a phenyldiazonium salt. The diazonium chloride was first converted to its piperidine triazene, which in turn was cleaved using hydrofluoric acid.

[PhN2]Cl + 2 C5H10NH → PhN=N-NC5H10 + [C5H10NH2]Cl
PhN=N-NC5H10 + 2 HF → PhF + N2 + [C5H10NH2]F

Historical note: in Wallach’s era, the element fluorine was symbolized with “Fl”. Thus, his procedure is subtitled “Fluorbenzol, C6H5Fl”.[3]

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[edit]

PhF is a relatively inert compound because the C–F bond is very strong. PhF is a useful solvent for highly reactive species, but a metal complex has been crystallized.[4]

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

See also[edit]

References[edit]

  1. ^ Table of Dielectric Constants of Pure Liquids. National Bureau of Standards. 1951.
  2. ^ Flood, D. T. (1943). "Fluorobenzene". Organic Syntheses.; Collective Volume, 2, p. 295.
  3. ^ Wallach, O. “Über einen Weg zur leichten Gewinnung organischer Fluorverbindungen” (Concerning a method for easily preparing organic fluorine compounds) Justus Liebig's Annalen der Chemie, 1886, Volume 235, p. 255–271; doi:10.1002/jlac.18862350303
  4. ^ R.N. Perutz and T. Braun “Transition Metal-mediated C–F Bond Activation” Comprehensive Organometallic Chemistry III, 2007, Volume 1, p. 725–758; doi:10.1016/B0-08-045047-4/00028-5.