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In the conversion of m-chloroanisole to m-anisidine using $\ce{NaNH2}$ and liquid $\ce{NH3}$, apparently the reason the $\ce{NH2-}$ goes for the meta- position instead of the para position is that, in the reaction mechanism for the conversion to m-anisidine, the benzyne intermediate involved has the triple bond closer to the $\ce{-OCH3}$ group than in the reaction to the para product, thus stabilizing the intermediate due to the stronger inductive effects of $\ce{-OCH3}$.

I know the triple bond in benzyne isn't exactly your typical triple bond, but is there always some(if negligible) stabilization of all multiple bonds through electron-withdrawing inductive effects?

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Since electron-withdrawing groups (EWGs) lower orbital energy (we can rationalise this in terms of reduced electron density leading to reduced shielding), they will stabilise multiple bonds - you see this in the Diels-Alder reaction, where EWGs on the dienophile reduce the energy of its LUMO and so accelerate the reaction by reducing the gap between the dienophile LUMO and diene HOMO (conversely, electron-donating groups on the diene destabilise its HOMO by the same logic and so also speed up the reaction).

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  • $\begingroup$ I don't know if I understand your reasoning here. EWG's lower the orbital energy of the multiple bond LUMO, but what does that say about the total energy of the molecule? OP is asking why one isomer is more stable than the other, and I don't think you can invoke LUMO lowering as an explanation. $\endgroup$
    – S R Maiti
    Apr 19 at 8:37
  • $\begingroup$ I should have been clearer - EWGs lower the orbital energy of all orbitals (including the LUMO), so by lowering energy of the occupied orbitals they will have a stabilising effect (the stabilisation of the LUMO is simply a specific example relevant to the Diels-Alder reaction). OP's question was specifically whether electron-withdrawing effects stabilise multiple bonds. $\endgroup$
    – atbm
    Apr 19 at 11:13

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