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Does the presence of substituents (electron withdrawing or electron donating) on an aromatic system have any effect on the aromatic character?

In other words, would it be correct to say that benzene has "greater" aromatic character than aniline? (Because in aniline, the lone pair on nitrogen can interact with the aromatic ring through delocalisation.)

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  • $\begingroup$ No, it's not correct. $\endgroup$
    – Mithoron
    Oct 4, 2021 at 20:12
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    $\begingroup$ One should look at the hydrogenation of the compounds you have in mind. You can start with toluene and do the classical analysis always presented for benzene. This would give an answer at least if aromaticity is treated as a thermochenical property. Another possibility is to compare H-NMR spectra using the idea of ring current. And so on. $\endgroup$
    – Alchimista
    Oct 5, 2021 at 9:41

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It is also a matter of usage of terms. Electron withdrawing substituents slow the rates of electrophilic substitution and the effect is usually expressed as increasing the energy of the intermediate-activated complex and not on changing the energy of the ground state. This makes some sense and it is easy to see the effect. However, electron rich compounds such as hydroquinone or aminophenols are very easily oxidized suggesting that the resonance orbitals are of higher energy. I have been unable to find heats of hydrogenation for various substituted benzenes, they might give a clue. At the moment without some actual data it might be fine to suggest some research either in the literature or in the lab into the subject. My feeling is that there is an effect and the data is already out there.

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