[davidenarb]

Hi all,

1. Can I have a short explanation about why aromatic compounds doesn't undergo addition with bromine?

2. Will aromatic compounds never undergo any type of addition reaction or just bromination addition? For example, Can we add H2O2, H2O, or HX across aromatic compounds?

Thank you

[salteen]

1.  Short answer:  Addition of Br₂ across an aromatic ring would result in a product that has lost its aromaticity.  Compounds usually don't want to give up aromaticity very easily, given that it is a very stabilizing feature.

2.  As far as I'm aware, this won't happen using traditional conditions for the same reasons outlined above.  But perhaps someone here with more experience knows of a more exotic approach that would work...

[davidenarb]

1.  Short answer:  Addition of Br₂ across an aromatic ring would result in a product that has lost its aromaticity.  Compounds usually don't want to give up aromaticity very easily, given that it is a very stabilizing feature.

2.  As far as I'm aware, this won't happen using traditional conditions for the same reasons outlined above.  But perhaps someone here with more experience knows of a more exotic approach that would work...

Thank you !!! it was short ans logical

[spirochete]

The birch reduction of benzene and benzene derivatives is technically an example of an addition reaction, which owes itself to the strong reducing power of alkali metals. Aromatic rings can also be hydrogenated fully under harsh conditions with hydrogen gas and catalytic metals. But mostly they do substitution reactions that result in maintaining aromaticity.

[zsinger]

As spirochete correctly said (as always), most are EAS or NAS reactions.  That "re-aromitaziton" downhill energy drive is so great when the Lewis acid gets reformed by snagging the hydrogen off the de-aromatized intermediate complex with the temporarily halogenated LA( (FeBr₄) at that stage for instance), one gets a quite favorable reaction.  Many other competing reactions are squashed because aromatic states are very stable.