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Preferred IUPAC name
Diphenyldiazene oxide[1]
Other names
(Z)-1,2-Diphenyldiazene 1-oxide
Molar mass 198.225 g·mol−1
Appearance yellow solid
Density 1.318 g/cm3
Melting point 35.5–36.5 °C (95.9–97.7 °F; 308.6–309.6 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Azoxybenzene is organic compound with the formula C6H5N(O)NC6H5. It is a yellow, low-melting solid.[2] The molecule has a planar C2N2O core. The N-N and N-O bond lengths are nearly the same at 1.23 Å.[3]


It can be prepared by partial reduction of nitrobenzene. This reaction is proposed to proceed via the intermediacy of phenylhydroxylamine and nitrosobenzene:[2]

PhNHOH + PhNO → PhN(O)NPh + H2O

Another option is the oxidation of aniline by hydrogen peroxide, in acetonitrile at 50 ºC. In this reaction, the pH should be kept around 8, to activate the hydrogen peroxide and avoid too much oxygen evolution at the same time. First, the acetonitrile is oxidized, forming an imine hydroperoxide. Then, this intermediate oxidizes the aniline to azoxybenzene. [4]

CH3CN + H2O2 → [CH3C(OOH)=NH]
2 PhNH2 + 3 [CH3C(OOH)=NH] → PhN(O)NPh + 3 CH3C(O)NH2 + 2 H2O
PhNO2 + Na3AsO3/NaOH→ Ph−N+O=N-Ph


  1. ^ a b c d Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 1009. doi:10.1039/9781849733069-00648. ISBN 978-0-85404-182-4.
  2. ^ a b H. E. Bigelow, Albert Palmer (1931). "Azoxybenzene". Organic Syntheses. 11: 16. doi:10.15227/orgsyn.011.0016.{{cite journal}}: CS1 maint: uses authors parameter (link)
  3. ^ S. P. G. Martínez, S. Bernès (2007). "trans-Diphenyldiazene Oxide". Acta Crystallographica Section E. 63 (8): o3639. doi:10.1107/S1600536807035787.{{cite journal}}: CS1 maint: uses authors parameter (link)
  4. ^ George B. Payne, Philip H. Deming, Paul H. Williams (1961). "Reactions of Hydrogen Peroxide. VII. Alkali-Catalyzed Epoxidation and Oxidation Using a Nitrile as Co-reactant". The Journal of Organic Chemistry. 26 (3): 659-663. doi:10.1021/jo01062a004.{{cite journal}}: CS1 maint: uses authors parameter (link)