I have searched for this answer for a long while but haven't got it. Why is diazobenzene named so and not phenyl diazobenzene or something? The group with two bonded nitrogens is the diazo group. Why does the term diazobenzene refer to a molecule with two benzene rings?

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    $\begingroup$ Does it?$\;\!\!$ $\endgroup$ Sep 13, 2018 at 14:15

1 Answer 1


Diazo group is $\ce{=N2}$.

Example: diazomethane $\ce{CH2=N2}$
(detailed structure: $\ce{H2C=N+=N- <-> H2C^{-}-N+\bond{#}N}$)

$\ce{-N=N-}$ is azo group.

Example: azomethane $\ce{CH3-N=N-CH3}$
However, preferred names are based on diazene $\ce{HN=NH}$, so better name for azomethane is dimethyldiazene.

So, note that “diazobenzene” does not exist. You obviously mean “azobenzene”, $\ce{C6H5-N=N-C6H5}$, whose preferred name is diphenyldiazene.

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    $\begingroup$ Actually my book had written diazobenzene, I think it was a misprint. $\endgroup$
    – Hema
    Sep 13, 2018 at 14:37
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    $\begingroup$ @Hema I wonder what the structure was.. there are similar compounds, diazonium salts, like $\ce{C6H5-N_{2}^{+} X^{-}}$ $\endgroup$
    – mykhal
    Sep 13, 2018 at 14:39
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    $\begingroup$ the structure in my book was of azobenzene $\endgroup$
    – Hema
    Sep 13, 2018 at 14:40

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