[Caeldom]

My teacher used bromine water as an example of a halogenation addition reaction with cyclohexene, to produce dibromocyclohexane. However, I’m a bit confused since in my textbook, it says 3-hexene will react with bromine water in a halohydration reaction, forming 4-bromo-3-hexanol. Is it just because one is cyclic and the other acyclic that the reactions differ?

Furthermore, I found out that bromine water partially disassociates into the equilibrium (leaning heavily to the left):

Br_2(l) + H₂O_(l) HOBr_(aq) + HBr_(aq)

Which means that there are both hypobromous acid and hydrogen bromide present in the solution as well. Doesn’t that mean they will all react with the hydrocarbon to form three or even four different products?

Or does it depend on the state of the reactant, the length of chain, concentrations etc... because to my understanding bromine will cause a halogenation, water will cause hydration, hypobromous acid will cause halohydration and hydrogen bromide will cause hydrohalogenation.

I also found out that this would all be simplified to a halogenation reaction if it were bromine in a non-aqueous solution. My teacher didn’t go into this much detail at all, though I haven’t had a chance to ask him specifically yet.


Also, what will be the favoured product in halohydration with unsymmetrical alkenes?

In a simple example like the reaction of 2-pentene with hypobromous acid:

CH3-CH=CH-CH2-CH3_(g) + HOBr_(aq)

will it form 3-bromo-2-pentanol, or 2-bromo-3-pentanol?

I know there’s Markovnikov’s Rule when it comes to hydrogen, but is there one for hydroxyl groups? Or perhaps it will form equal amounts of both?


Cheers,
Dan

[Caeldom]

For some reason I can't modify my original post above, but I believe I might receive a response in the organic forum so I've posted the question there as well, however I know it would be better to just move this topic, but I'm not sure how soon it can be moved and whether I would get an answer faster this way. So sincere apologies for violating a red rule, and if a moderator/admin sees this, you can delete my other topic (if there are no replies), then move this one accordingly, or move the replies etc (not sure what the extent of Simple Machines' administration features are).