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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: BioFelix on November 25, 2020, 03:02:10 AM

Title: Electrophilic addition of Halogen and Water (Halohydrin) on Alkenes??
Post by: BioFelix on November 25, 2020, 03:02:10 AM
I am currently learning for an organic chemistry test and I just couldn't come up with a solution to the following question:
Consider the reaction of 2-Propen + Br2 with water as solvent.
Why will the nucleophilic water molecule add on C-2 and rather than on C1 of the Bromonium-Ion?
The answer seems to be, because in the transition state the bonding between Br and C will dissociate quicker than the bonding between O and C will form, which leads to a positive charge on that C-Atom in the transition state and therefore water will add on the more stable "carbokation-like" carbon.
My question is: why does the Br-C bonding dissociate quicker than the O-C bonding forms? (I read that in the pearson organic chemistry textbook). Does it have anything to do with the Hammond-postulate? Or are there any other thermodynamic or kinetics reasons?
Unfortunately I haven't found an answer on the internet yet and also not in other textbooks.
Maybe you can help :) Thanks!