Nitrosobenzene

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.

Additional recommended knowledge

How to quickly check pipettes?

What is the Correct Way to Check Repeatability in Balances?

Don't let static charges disrupt your weighing accuracy

Preparation

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

• 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.; 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