Posts Tagged ‘Meisenheimer’

Concerted vs stepwise (Meisenheimer) mechanisms for aromatic nucleophilic substitution.

Monday, March 25th, 2013
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My two previous explorations of aromatic substitutions have involved an electrophile (NO+ or Li+). Time now to look at a nucleophile, representing nucleophilic aromatic substitution. The mechanism of this is thought to pass through an intermediate analogous to the Wheland for an electrophile, this time known as the Meisenheimer complex[1]. I ask the same question as before; are there any circumstances under which the mechanism could instead be concerted, by-passing this intermediate?

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References

  1. J. Meisenheimer, "Ueber Reactionen aromatischer Nitrokörper", Justus Liebig's Annalen der Chemie, vol. 323, pp. 205-246, 1902. http://dx.doi.org/10.1002/jlac.19023230205