Benzenediazonium tetrafluoroborate

Benzenediazonium tetrafluoroborate
	; The benzenediazonium ion
Names
	IUPAC name Benzenediazonium chloride
	Other names Phenyldiazonium chloride
Identifiers
CAS Number	100-34-5 ;
3D model (JSmol)	Interactive image;
ChemSpider	54953 ;
PubChem CID	60992;
UNII	3U50A1GI4F ;
	InChI InChI=1S/C6H5N2.ClH/c7-8-6-4-2-1-3-5-6;/h1-5H;1H/q+1;/p-1 Key: CLRSZXHOSMKUIB-UHFFFAOYSA-M ; InChI=1/C6H5N2.ClH/c7-8-6-4-2-1-3-5-6;/h1-5H;1H/q+1;/p-1 Key: CLRSZXHOSMKUIB-REWHXWOFAT;
	SMILES [Cl-].N#[N+]c1ccccc1;
Properties
Chemical formula	C6H5ClN2
Molar mass	140.57 g·mol−1
Appearance	colorless crystals
Melting point	decomposes
Boiling point	decomposes
Solubility in water	very good, hydroscopic
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	unstable at temperature exceeding 278K (5C), possibly explosive
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Benzenediazonium chloride is an organic compound with the formula [C₆H₅N₂]Cl. It is a salt of a diazonium cation and chloride. It exists as a colourless solid that is soluble in polar solvents including water. It is the parent member of the aryldiazonium compounds,^[1] which are widely used in organic chemistry. Because the salt is unstable, it is not commercially available but is prepared upon demand.

Synthesis

This compound is prepared by diazotization of aniline in the presence of hydrochloric acid:^[2] The conversion involves in situ production of nitrous acid (HNO₂), which reacts with the aniline:

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

The reactions are conducted at low temperature to minimize decomposition of the diazonium salt. The diazonium salt is not isolated.

Benzenediazonium tetrafluoroborate

Benzenediazonium tetrafluoroborate can be obtained from crude benzenediazonium chloride by salt metathesis using tetrafluoroboric acid. The tetrafluoroborate is more stable.^[2]

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.

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

Safety

The compound is explosive.^[4]

References

^ March, J. (1992). Advanced Organic Chemistry (4th ed.). New York: J. Wiley and Sons. ISBN 0-471-60180-2.
^ ^a ^b Flood, D. T. (1933). "Fluorobenzene". Org. Synth. 13: 46. doi:10.15227/orgsyn.013.0046..
^ Hartman, W. W.; Dickey, J. B. (1934). "Diazoaminobenzene". Organic Syntheses. 14: 24. doi:10.15227/orgsyn.014.0024.
^ Nesmajanow, A. N. (1932). "β-Naphthylmercuric chloride". Organic Syntheses. 12: 54; Collected Volumes, vol. 2, p. 432.

[1] March, J. (1992). Advanced Organic Chemistry (4th ed.). New York: J. Wiley and Sons. ISBN 0-471-60180-2.

[OS-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] Nesmajanow, A. N. (1932). "β-Naphthylmercuric chloride". Organic Syntheses. 12: 54; Collected Volumes, vol. 2, p. 432.

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