Is this an error? Why is the nitro group reduced as the benzene ring is oxidized? I don't see any possible reducing agents here..

Also, what is the mechanism of aromatic fluorination by xenon difluoride? This appears analogous to electrophilic aromatic substitution in which benzene acts as a nucleophile and attacks an electrophile because of the expected meta-substitution pattern given the presence of the nitro group.

Is fluorine really electrophilic here? How so?

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1 Answer 1


The reaction as pictured above is incorrect, the nitro group is not reduced. As you suggest this is (predominantly) an electrophilic aromatic substitution reaction.

Usually $\ce{HF}$ is used as a catalyst in these reactions and the following equilibrium is established.

$$\ce{XeF2 + HF <=> XeF+ + HF2^-}$$

The electrophilic $\ce{XeF^+}$ is the reactive species forming a complex with the aromatic ring. Xenon is expelled from the complex and the reaction proceeds to yield the meta-fluoro isomer as expected for an electrophilic aromatic substitution. Some other products, such as substituted biphenyls, are usually formed in small amounts suggesting that some minor pathway (radical-cation?) is also in play.


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