Coupling in benzene derivatives

The ortho coupling in benzene derivatives varies over the relatively small range of 6.7-8.5 Hz, depending on the resonance and inductive effects of the substituents. The presence of heteroatoms in the ring expands the range at the lower end down to 2 Hz, because of the effects of electronegativity (pyridines) and of smaller rings (furans and pyrroles). 

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