Nitrosobenzene

Nitrosobenzene

Names
IUPAC name Nitrosobenzene
Identifiers
CAS Number	586-96-9
3D model (Jmol)	Interactive image
ChEBI	CHEBI:27986
ChEMBL	ChEMBL98797
ChemSpider	10989
ECHA InfoCard	100.008.721
KEGG	C06876
PubChem	11473
RTECS number	DA6497525
InChI InChI=1S/C6H5NO/c8-7-6-4-2-1-3-5-6/h1-5H Key: NLRKCXQQSUWLCH-UHFFFAOYSA-N InChI=1/C6H5NO/c8-7-6-4-2-1-3-5-6/h1-5H Key: NLRKCXQQSUWLCH-UHFFFAOYAR
SMILES O=Nc1ccccc1
Properties
Chemical formula	C6H5NO
Molar mass	107.11 g·mol^−1
Appearance	Colorless solid
Melting point	65 to 69 °C (149 to 156 °F; 338 to 342 K)
Boiling point	59 °C (138 °F; 332 K) (at 18 mmHg)
Solubility in water	Low
Solubility in other solvents	Sol. in organic solvents
Structure
Molecular shape	N is sp^2
Hazards
Main hazards	toxic
R-phrases	R20/21–R25
S-phrases	S26–S36/37–S45
Related compounds
Related compounds	Nitrobenzene Aniline
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Nitrosobenzene is the organic compound with the formula C₆H₅NO. This diamagnetic species exists in equilibrium with its dimer.

Preparation

Nitrosobenzene 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 sodium dichromate (Na₂Cr₂O₇).^[2]

Nitrosobenzene 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

Nitrosobenzene undergoes Diels–Alder reactions with dienes.^[4] Condensation with anilines affords azobenzene derivatives in a reaction known as the Mills reaction.^[5] Reduction of nitrosobenzene produces aniline.

Most characteristically, nitrosobenzene condenses with active methylene groups, such as those of malonic esters and benzyl cyanide. For example, condensation with benzylcyanide (PhCH₂CN) gives the imine (PhC(CN)=NPh) in a reaction known as the Ehrlich-Sachs Reaction:^[6]

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

References

1. Baeyer, A. (1874). "Nitrosobenzol und Nitrosonaphtalin". Chemische Berichte. 7: 1638–1640. doi:10.1002/cber.187400702214.
2. G. H. Coleman, C. M. McCloskey, F. A. Stuart (1955). "Nitrosobenzene". Org. Synth.; Coll. Vol., 3, p. 668
3. H. Caro (1898). Z. angew. Chem. 11: 845ff. Missing or empty |title= (help)
4. H. Yamamoto, N. Momiyama "Rich Chemistry of Nitroso Compounds" Chemical Communications 2005, pp.3514–25.
5. H. D. Anspon (1955). "p-Phenylazobenzoic Acid". Org. Synth.; Coll. Vol., 3, p. 711
6. H. Feuer. S. Patai, ed. The Chemistry of the Nitro and Nitroso Groups Part 1. New York: Wiley. pp. 278–283. Missing or empty |title= (help)
7. "Asymmetric O− and N− Nitroso Aldol Reaction – an efficient access to a-oxy and a-amino carbonyl compound" (PDF).