Benzenediazonium tetrafluoroborate

Benzenediazonium tetrafluoroborate
Names
IUPAC name
Benzenediazonium tetrafluoroborate
Other names
Phenyldiazonium tetrafluoroborate
Identifiers
3D model (JSmol)
ChemSpider
EC Number
  • 820-352-6
  • 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
  • [B-](F)(F)(F)F.C1=CC=C(C=C1)[N+]#N
Properties
C6H5BF4N2
Molar mass 191.92 g·mol−1
Appearance colorless crystals
Density 1.565 g/cm3
Melting point 77 °C (171 °F; 350 K)
Boiling point Decomposes at 91 °C (196 °F; 364 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X markN (what is checkYX markN ?)

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, which are widely used in organic chemistry.

Synthesis

Diazotization of aniline with nitrous acid in the presence of hydrochloric acid gives phenyldiazonium chloride:

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

The required nitrous acid can be generated in situ by combining sodium nitrite and hydrochloric acid. The tetrafluoroborate salt of phenyl diazonium can be obtained from benzenediazonium chloride by salt metathesis using tetrafluoroboric acid.

[C6H5N2]Cl + HBF4 → [C6H5N2]BF4 + HCl

The tetrafluoroborate is more stable than the chloride.

Properties

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.

Reaction with aniline gives 1,3-diphenyltriazene.

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

Safety

While tetrafluoroborate salts are typically less sensitive than chlorides, all aryldiazonium salts should be assumed to pose a risk of explosion "unless proved otherwise".

Benzenediazonium tetrafluoroborate has been described as shock-insensitive, and, when dry, decomposes smoothly upon heating. It is less sensitive than benzenediazonium chloride, which is liable to detonate upon exposure to heat, friction, or shock.

References

  1. 1 2 Souza, Edson Leonardo Scarpa de; Chorro, Tomaz Henrique Duarte; Correia, Carlos Roque Duarte (September 2023). "Thermal analysis of arenediazonium tetrafluoroborate salts: Stability and hazardous evaluation". Process Safety and Environmental Protection. 177: 69–81. doi:10.1016/j.psep.2023.06.082.
  2. ↑ March, J. (1992). Advanced Organic Chemistry (4th ed.). New York: J. Wiley and Sons. ISBN 0-471-60180-2.
  3. ↑ Henry M. Leicester (1938). "Diphenyl Selenide". Organic Syntheses. 18: 27. doi:10.15227/orgsyn.018.0027.
  4. 1 2 Flood, D. T. (1933). "Fluorobenzene". Org. Synth. 13: 46. doi:10.15227/orgsyn.013.0046.
  5. ↑ Hartman, W. W.; Dickey, J. B. (1934). "Diazoaminobenzene". Organic Syntheses. 14: 24. doi:10.15227/orgsyn.014.0024.
  6. ↑ 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.
  7. ↑ Firth, James D.; Fairlamb, Ian J. S. (18 September 2020). "A Need for Caution in the Preparation and Application of Synthetically Versatile Aryl Diazonium Tetrafluoroborate Salts". Organic Letters. 22 (18): 7057–7059. doi:10.1021/acs.orglett.0c02685.
  8. ↑ Maas, Gerhard; Tanaka, M.; Sakakura, Toshiyasu (15 April 2001). "Benzenediazonium Tetrafluoroborate". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rb009.
  9. ↑ Coates, Robert M.; Denmark, Scott E., eds. (1999). Handbook of Reagents for Organic Synthesis. Vol. 6: Reagents, Auxiliaries, and Catalysts for C–C Bond Formation. Chichester, West Sussex, UK: Wiley. p. 83. ISBN 0-471-97924-4.
  10. ↑ Maas, Gerhard (15 April 2001). "Benzenediazonium Chloride". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rb007.