# Bromination of an alkene in presence of water

Bromination of an alkene in presence of water results in its mechanism in a cyclic bromonium ion and "afterwards $$\ce{H2O}$$ binds to the carbon atom surrounded by more electron donating groups." This is what we learned in class and I couldn't understand why. Shouldn't an electron donating group decrease the "strength" of an electrophile?

Also to my surprise, in an exercise, $$\ce{H2O}$$ was added to the formerly $$sp2$$ carbon bonded to $$\ce{-OCH3}$$ which donates electrons by resonace in an alkene. But $$\ce{H2O}$$ was added to the cyclic bromonium and not to the alkene directly! So why to care about the resonance effect of $$\ce{-OCH3}$$?

• Electron donation stabilises the carbocation so that it hangs around long enough to react with a nucleophile – Waylander Sep 20 at 13:47
• But carbocations are not formed in halogenation mechanism of alkenes – user208973 Sep 20 at 13:54
• they are formed as an equilibrium form of the cyclic bromonium ion, particularly if stabilised – Waylander Sep 20 at 14:25