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At which position will electrophilic substitution on p-cyanonitrobenzene occur?

As both are -M groups, there are two possible sites of reaction, meta to each of the groups.
The answer is meta to $\ce{CN-}$. Why is this so? According to me it should be meta to $\ce{NO2}$, because $\ce{NO2}$ is the stronger -M group?

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  • $\begingroup$ Welcome to Chemistry.SE. Take the tour to get familiar with this site. This appears to be a homework question, please share your thoughts and attempts towards the solution. It'll make us certain that ‎we aren't doing your homework for you. $\endgroup$
    – user15489
    Commented Aug 27, 2015 at 9:11
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    $\begingroup$ For such compound most eletrophilic subst. wouldn't work $\endgroup$
    – Mithoron
    Commented Aug 27, 2015 at 12:15

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As Mithoron suggests, the correct answer is probably "no reaction." There are no examples of electrophilic aromatic substitution of p-cyanonitrobenzene in SciFinder, by the introductory organic chemistry mechanism at least.

There is one report of halogenation (with N-halosuccinimide) of this compound with palladium catalysis. The cyano group serves as a directing group to place a halogen ortho to the cyano. Chlorination and bromination are both reported.

Reference: Palladium-Catalyzed Highly Selective ortho-Halogenation (I, Br, Cl) of Arylnitriles via sp2 C–H Bond Activation Using Cyano as Directing Group

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  • $\begingroup$ Do you mean that there is no such reaction at all ? $\endgroup$ Commented Aug 28, 2015 at 6:05
  • $\begingroup$ @arutoregni using the typical conditions. For example, reaction of p-cyanonitrobenzene with bromine and iron tribromide has never been reported in the literature. Halogenation has been accomplished by a different mechanism, which is what is described in the answer. $\endgroup$
    – jerepierre
    Commented Aug 28, 2015 at 15:54

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