benzenediazonium tetrafluoroborate
{{short description|Organic compound containing an –N≡N+ function}}
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| verifiedrevid =
| ImageFile = PhN2BF4.svg
| ImageSize = 160px
| ImageFile1 = PhN2BF4.jpg
| ImageSize1 = 200px
| IUPACName = Benzenediazonium tetrafluoroborate
| OtherNames = Phenyldiazonium tetrafluoroborate
|Section1={{Chembox Identifiers
| CASNo_Ref =
| CASNo = 369-57-3
| UNII_Ref = {{fdacite|changed|FDA}}
| UNII =
| PubChem = 5284485
| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}
| ChemSpiderID=4447548
| EC_number = 820-352-6
| StdInChI=1S/C6H5N2.BF4/c7-8-6-4-2-1-3-5-6;2-1(3,4)5/h1-5H;/q+1;-1
| StdInChIKey = JNCLVGMBRSKDED-UHFFFAOYSA-N
| SMILES = [B-](F)(F)(F)F.C1=CC=C(C=C1)[N+]#N
}}
|Section2={{Chembox Properties
| C=6 | H=5 | N=2 | B=1|F=4
| Appearance = colorless crystals
| Density = 1.565 g/cm3
| MeltingPt = decomposes
| BoilingPt = decomposes
| Solubility = }}
|Section3={{Chembox Hazards
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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,{{ cite book | author = March, J. | title = Advanced Organic Chemistry | edition = 4th | publisher = J. Wiley and Sons | year = 1992 | location = New York | isbn = 0-471-60180-2 }} which are widely used in organic chemistry.
Synthesis
Diazotization of aniline:
: C6H5NH2 + HNO2 (from NaNO2 and HCl) + 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.{{cite journal |journal=Org. Synth.| author = Flood, D. T. | year = 1933 | title = Fluorobenzene | volume = 13 | pages = 46 | doi = 10.15227/orgsyn.013.0046}}
Properties
{{main|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.{{cite journal| author = Hartman, W. W.| author2 = Dickey, J. B.| title = Diazoaminobenzene | journal = Organic Syntheses | volume = 14 | pages = 24 | year = 1934 | doi= 10.15227/orgsyn.014.0024}}
The structure of the salt has been verified by X-ray crystallography. The N-N bond distance is 1.083(3) Å.{{cite journal|doi=10.1139/v82-407|title=The Crystal Structure of Benzenediazonium Tetrafluoroborate, C6H5N2+•BF4−1|year=1982|last1=Cygler|first1=Miroslaw|last2=Przybylska|first2=Maria|last3=Elofson|first3=Richard Macleod|journal=Canadian Journal of Chemistry|volume=60|issue=22|pages=2852–2855|doi-access=free}}
Safety
Whereas the chloride salt is explosive,{{OrgSynth | author = Nesmajanow, A. N. | title = β-Naphthylmercuric chloride | year = 1932 | volume = 12 | pages = 54 | collvol = 2 | collvolpages = 432 | prep = cv2p0432 }} the tetrafluoroborate is readily isolated.