Benzenediazonium chloride

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Benzenediazonium chloride
The benzenediazonium ion
CAS number 100-34-5 YesY
PubChem 60992
ChemSpider 54953 YesY
Jmol-3D images Image 1
Molecular formula C6H5ClN2
Molar mass 140.57 g mol−1
Appearance colorless crystals
Melting point decomposes
Boiling point decomposes
Solubility in water very good, hydroscopic
Main hazards unstable, possibly explosive
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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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. It is representative of a family of aryldiazonium compounds that are used to prepare azo dyes.[1]


Method 1[edit]

This compound is easily prepared by ordinary methods of diazotization: by dissolving aniline in ice-cold hydrochloric acid, followed by addition of sodium nitrite.[2] This mixture produces nitrous acid (HNO2), which proceed to react with the aniline:

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

The temperature must be controlled to avoid the product decomposition. Due to its instability, this salt is not commercially available.

Method 2[edit]

Diazonium chloride is also prepared by treating nitrite esters with aniline in presence of HCl. Nitrite esters are formed from alcohol and nitrous acid.[3]

C5H11ONO + HCl + C6H5NH2 → [C6H5N2]Cl + C5H11OH + H2O

Physical properties[edit]

Benzenediazonium chloride is a colourless crystalline solid. It is readily soluble in water but less soluble in alcohol. It turns brown on exposure to air.

Chemical properties[edit]

Main article: Diazonium compound

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

C6H5N+ + 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.


Workers have mentioned the violent decomposition of this compound.[4]


  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 ; Coll. Vol. 2: 295  This procedure described the tetrafluoroborate salt of phenyldiazonium.
  3. ^ Jain, S. K. (2009). Conceptual Chemistry for class XII. New Delhi: S. Chand & Company. pp. 1179–1183. ISBN 81-219-1623-2. 
  4. ^ Nesmajanow, A. N. (1932), "β-Naphthylmercuric chloride", Org. Synth. 12: 54 ; Coll. Vol. 2: 432