Benzene electron donating / withdrawing

[Lifeman]

EK / O-Chem / Lec. 3 / Q. 63

There is an ester attached to a benzene. The molecule is methyl benzoate.
The question is asking which substituent on the benzene ring would make the methyl benzoate less reactive.

They said it is NO2 because electron withdrawing substituents stabilize the methyl benzoate.
I thought it would be an electron donating group since the ester reacts at the carbonyl carbon. A nucleophile attacks the partial positive on the carbonyl carbon, so if I can donate negative charges to the carbon, it will be less reactive.

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[Trayshawn]

You're thinking about carbonyl (ester) chemistry when they're clearly hinting at aromaticity.
Electron donating groups activate aromatic compounds thus promoting electrophilic aromatic subsitution (EAS). Electron withdrawing groups deactivate aromatic compounds towards EAS. Thus, NO2 is a good option.

 

[Lifeman]

That makes sense, thanks. It's confusing because I just learned how benzene being an electron withdrawing group itself, makes a phenol more acidic than a regular alcohol - and benzene substituents that withdraw electron density even more, make the phenol even more acidic. I don't Iike this question because the carbonyl has nothing to do with the question then, if all we are talking about is EAS.

 

[straight2thapros]

Just because the question is leading you to think about EAS doesn't mean that we should assume "less reactive in terms of EAS" right?! Is it possible this is just a bad question? I too, focused on the ester reactivity and not the EAS. it seems to me if there is already an ester (strong deactivating group) attached to the ring the rxn that the focus is on how the ester reacts not the ring (if not provided any numbers about their reaction rates). Unfortunately I can't find anything (my Ochem book, internet) to support my theory (i.e. that the ester reaction is the reaction that is "more reactive" and thus the one you should focus on if trying to affect reactivity).

How can we know for a question like this if it's trying to focus our attention or misdirect?