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)[1]
Boiling point Decomposes at 91 °C (196 °F; 364 K)[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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,[2] 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.[3] 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.[4]

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.

Reaction with aniline gives 1,3-diphenyltriazene.[5]

The structure of the salt has been verified by X-ray crystallography. The N-N bond distance is 1.083(3) Å.[6]

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".[7]

Benzenediazonium tetrafluoroborate has been described as shock-insensitive,[8][9] and, when dry, decomposes smoothly upon heating.[4] It is less sensitive than benzenediazonium chloride, which is liable to detonate upon exposure to heat, friction, or shock.[10]

References

  1. ^ a b 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. ^ a b 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.
allikas: https://en.wikipedia.org/wiki/Benzenediazonium_cation