Benzenediazonium tetrafluoroborate

Benzenediazonium tetrafluoroborate

Names
IUPAC name Benzenediazonium tetrafluoroborate
Other names Phenyldiazonium tetrafluoroborate
Identifiers
CAS Number	369-57-3
3D model (JSmol)	Interactive image
ChemSpider	4447548^N
EC Number	820-352-6
PubChem CID	5284485
InChI InChI=1S/C6H5N2.BF4/c7-8-6-4-2-1-3-5-6;2-1(3,4)5/h1-5H;/q+1;-1 Key: JNCLVGMBRSKDED-UHFFFAOYSA-N
SMILES [B-](F)(F)(F)F.C1=CC=C(C=C1)[N+]#N
Properties
Chemical formula	C6H5BF4N2
Molar mass	191.92 g·mol^−1
Appearance	colorless crystals
Density	1.565 g/cm^3
Melting point	decomposes
Boiling point	decomposes
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N (what is ^YN ?) Infobox references

Benzenediazonium tetrafluoroborate is an organic compound with the formula [C₆H₅N₂]BF₄. It is a salt of a diazonium cation and tetrafluoroborate. It exists as a colourless solid that is soluble in polar solvents. It is the parent member of the aryldiazonium compounds,[1] which are widely used in organic chemistry.

Synthesis

Diazotization of aniline in the presence of hydrochloric acid:

C₆H₅NH₂ + HNO₂ + HCl → [C₆H₅N₂]Cl + 2 H₂O

The tetrafluoroborate can be obtained from crude benzenediazonium chloride by salt metathesis using tetrafluoroboric acid.

[C₆H₅N₂]Cl + HBF₄ → [C₆H₅N₂]BF₄ + HCl

The tetrafluoroborate is more stable than the chloride.[2]

Properties

Main article: Diazonium compound

The diazo group (N₂) can be replaced by many other groups, usually anions, giving a variety of substituted phenyl derivatives:

C₆H₅N₂^+ + Nu^− → C₆H₅Nu + N₂

These transformations are associated with many named reactions including the Schiemann reaction, Sandmeyer reaction, and Gomberg-Bachmann reaction. A wide range of groups that can be used to replace N₂ including halide, SH^−, CO₂H^−, OH^−. Of considerable practical value in the dye industry are the diazo coupling reactions.

The reaction of phenyldiazonium salts with aniline gives 1,3-diphenyltriazene.[3]

The structure of the salt has been verified by X-ray crystallography. The N-N bond distance is 1.083(3) Å.[4]

Safety

Whereas the chloride salt is explosive,[5] the tetrafluoroborate is readily isolated.

References

1. March, J. (1992). Advanced Organic Chemistry (4th ed.). New York: J. Wiley and Sons. ISBN 0-471-60180-2.
2. Flood, D. T. (1933). "Fluorobenzene". Org. Synth. 13: 46. doi:10.15227/orgsyn.013.0046.
3. Hartman, W. W.; Dickey, J. B. (1934). "Diazoaminobenzene". Organic Syntheses. 14: 24. doi:10.15227/orgsyn.014.0024.
4. Cygler, Miroslaw; Przybylska, Maria; Elofson, Richard Macleod (1982). "The Crystal Structure of Benzenediazonium Tetrafluoroborate, C₆H₅N₂^+•BF₄^−1". Canadian Journal of Chemistry. 60 (22): 2852–2855. doi:10.1139/v82-407.
5. Nesmajanow, A. N. (1932). "β-Naphthylmercuric chloride". Organic Syntheses. 12: 54; Collected Volumes, vol. 2, p. 432.