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Systematic name Nitrosobenzene
Other names  ?
Molecular formula C6H5NO
SMILES O=Nc1ccccc1
Molar mass 107.11 g/mol
Appearance colourless solid
CAS number [586-96-9]
Density and phase  ? g/cm3, ?
Solubility in water low
Other solvents sol. in organic solvents
Melting point 65-69 °C
Boiling point 59 °C, 18 mm Hg
Acidity (pKa)  ?
Viscosity  ? cP at ? °C
Molecular shape N is sp2
Dipole moment  ? D
MSDS External MSDS
Main hazards toxic
NFPA 704
Flash point  ? °C
R/S statement R: 20/21-25
S: 26-36/37-45
RTECS number DA6497525
Supplementary data page
Structure and
n, εr, etc.
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
Related compounds
Related compounds Nitrobenzene
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Infobox disclaimer and references

Nitrosobenzene is the organic compound with the formula C6H5NO. The compound can be viewed as hybrid of singlet O2 and azobenzene. This diamagnetic species exists in equilibrium with its dimer.



C6H5NO was first prepared by Adolf von Baeyer by the reaction of diphenylmercury and nitrosylbromide:[1]

[C6H5]2Hg + BrNO → C6H5NO + C6H5HgBr

The modern synthesis entails reduction of nitrobenzene to phenylhydroxylamine, C6H5NHOH, which is then oxidized by Na2Cr2O7.[2] C6H5NO can also be prepared by oxidation of aniline using peroxymonosulfuric acid, Caro's acid.[3] It is usually purified by steam distillation, where it comes over as a green liquid that solidifes to a colorless solid.

Characteristic reactions

The monomer undergoes Diels-Alder reactions with dienes.[4] Most characteristically nitrosobenzene condenses with "active" methylene and amine groups, e.g. of malonic esters. Condensation with anilines affords azobenzene derivatives (Mills reaction)[5] and condensation with benzylcyanide PhCH2CN the imine PhC(CN)=NPh (The Ehrlich-Sachs Reaction).[6]

Reduction of PhNO produces C6H5NH2.

See also


  1. ^ Baeyer, A. "Nitrosobenzol und Nitrosonaphtalin" Chemische Berichte 1874, volume 7, pp.1638–1640.
  2. ^ G. H. Coleman, C. M. McCloskey, F. A. Stuart (1955). "Nitrosobenzene". Org. Synth.; Coll. Vol. 3: 668. 
  3. ^ H. Caro, Z. angew. Chem., volume 11, p 845ff (1898).
  4. ^ H. Yamamoto, N. Momiyama "Rich Chemistry of Nitroso Compounds" Chemical Communications 2005, pp.3514–3525.
  5. ^ H. D. Anspon (1955). "p-Phenylazobenzoic Acid". Org. Synth.; Coll. Vol. 3: 711. 
  6. ^ H. Feuer in S. Patai (ed.) "The Chemistry of the Nitro and Nitroso Groups Part 1," Wiley: New York. pp. 278-283
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Nitrosobenzene". A list of authors is available in Wikipedia.
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