Nitrosobenzene

Nitrosobenzene
IUPAC name Nitrosobenzene
Other names ?
Identifiers
CAS number	586-96-9 Y
PubChem	11473
ChemSpider	10989 Y
KEGG	C06876 Y
ChEBI	CHEBI:27986 N
ChEMBL	CHEMBL98797 Y
RTECS number	DA6497525
Jmol-3D images	Image 1
SMILES O=Nc1ccccc1
InChI InChI=1S/C6H5NO/c8-7-6-4-2-1-3-5-6/h1-5H Y Key: NLRKCXQQSUWLCH-UHFFFAOYSA-N Y InChI=1/C6H5NO/c8-7-6-4-2-1-3-5-6/h1-5H Key: NLRKCXQQSUWLCH-UHFFFAOYAR
Properties
Molecular formula	C6H5NO
Molar mass	107.11 g/mol
Appearance	colourless solid
Density	? g/cm3, ?
Melting point	65-69 °C
Boiling point	59 °C, 18 mm Hg
Solubility in water	low
Solubility in other solvents	sol. in organic solvents
Structure
Molecular shape	N is sp2
Hazards
R-phrases	20/21-25
S-phrases	26-36/37-45
Main hazards	toxic
Related compounds
Related compounds	Nitrobenzene Aniline
N (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox 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.

Preparation

C₆H₅NO was first prepared by Adolf von Baeyer by the reaction of diphenylmercury and nitrosyl bromide:^[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] Condensation with anilines affords azobenzene derivatives (Mills reaction)^[5]. Reduction of PhNO produces C₆H₅NH₂.

Most characteristically nitrosobenzene condenses with "active" methylene groups, e.g. of malonic esters, benzyl cyanide etc. For example, condensation with benzylcyanide PhCH₂CN gives the imine PhC(CN)=NPh (The Ehrlich-Sachs Reaction)^[6] :

Ph-CH₂-CN + Ph-NO → Ph-CH(CN)-N(OH)-Ph (oxyamination adduct) → PhC(CN)=N(OH)Ph

Sometimes condensation with "active" methylene compounds could give products of O-nitroso-aldol reaction ^[7]:

R-CH₂-CHO + Ph-NO → R-CH(CHO)-O-NHPh (aminoxylation adduct)

See also

• Nitroso

References

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., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV3P0668 ; 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., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV3P0711 ; 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
7. ^ Asymmetric O- and N- Nitroso Aldol Reaction - an efficient access to a-oxy and a-amino carbonyl compound