Deactivating group

[Power12]

Would benzoic acid reacting with Br2/FeBr3 be a deactivator or activator? I understand that strongly activating groups over shadowing the deactivating ones. OH would be activating and the carbonyl deactivating....therefore, should the Br be para or meta?

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[AlbinoPolarBear]

Would benzoic acid reacting with Br2/FeBr3 be a deactivator or activator? I understand that strongly activating groups over shadowing the deactivating ones. OH would be activating and the carbonyl deactivating....therefore, should the Br be para or meta?

You got to look at the group as a whole, not separately as OH and carbonyl.

Carboxylic acids are DEACTIVATING and meta directing.

 

[boomchakalak]

Would benzoic acid reacting with Br2/FeBr3 be a deactivator or activator? I understand that strongly activating groups over shadowing the deactivating ones. OH would be activating and the carbonyl deactivating....therefore, should the Br be para or meta?

The carbon on the carboxylic acid has a partially positive charge due to the electronegativity difference between carbon bearing the carboxylic acid and the electron greedy oxygen. This makes the carboxylic acid functional group an electron withdrawing group because the partially positive carbon wants electrons to neutralize itself and compensates by withdrawing electrons from the benzene ring.

The addition of Br2/FeBr3 is a EAS (Electrophilic Aromatic Substitution) reaction where the benzene ring is the nucleophile. When benzene has an electron withdrawing group present on it, it becomes less electron rich and thus a worse nucleophile, therefore carboxylic acid is a deactivating functional group.