[pradeepk]

Hey Guys,

I attached the problem. I get so confused on these types of problems.  I understand that Br2 and H20 add Br and OH to the double bond, but I have no idea what to do after that.  How can you possible make a ring?  Any help would be appreciated.  Thanks!

[UG]

When you add Br₂ what is the intermediate formed?
Water can act as a nucleophile but what else can act as a nucleophile?

[pradeepk]

When you add Br2, you get a bridged halonium ion intermediate.  So normally H2O would act as the nucleophile and break the bridge...but I suppose that the lone pair from the hydroxyl group could attack it instead?  Ahh I see..so that is how you get the ring structure?

[UG]

...but I suppose that the lone pair from the hydroxyl group could attack it instead?  Ahh I see..so that is how you get the ring structure?

Very good! 

[pradeepk]

...but I suppose that the lone pair from the hydroxyl group could attack it instead?  Ahh I see..so that is how you get the ring structure?

Very good!  

Thanks for the *delete me* My only question is..what is the point of H2O being in the reaction if it isnt used?

[pradeepk]

nevermind! i think i got it.  AFter the attack of the lone pair from the hydroxyl there is a positive charge, so that is where the H2O comes in i think.