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Can an Electron Withdrawing Group(EWG)(like NO2, F, Cl, OH, etc.) behave as a Electron Donating group(EDG) in a compound where a carbocation is present in order to stabilise it?

Does the position where it is present or distance from the carbocation affect it's behaviour as an EWG or EDG?

I feel that it should behave as an EDG as carbocation is electron deficient so it has a greater tendency to accept an electron.

Can we say a similar thing that an EDG behaves as an EWG in presence of carbanion as it has excess electrons?

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Of course not. That's why it is called EDG or EWG. It tends to destabilize it more in the absence of other effects like resonance and hyperconjugation.

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  • $\begingroup$ I'm afraid this may be an oversimplification; atoms care not for how we categorise them. For example, the fact that halide substituents on a phenyl ring are deactivating/electron-withdrawing yet ortho/para-directing suggests there can be simultaneous electron-withdrawing and electron-donating effects in operation, which in this case happens to have a net withdrawing effect. Now what if a bromine atom was linked to 2,4,6-trinitrobenzene? Or a pyrimidine ring? Would it still have a net electron-withdrawing effect into the ring? I have wondered this for a while myself. $\endgroup$ – Nicolau Saker Neto Oct 24 '18 at 8:48

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