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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: owlpower on October 21, 2018, 02:35:17 AM

Title: Representing product of alkene hydration
Post by: owlpower on October 21, 2018, 02:35:17 AM
Here is a hydration reaction. I know that BH3 and OH- is used, so this will be a anti-Markovnikov, syn addition.

However, I am not exactly sure how to represent the addition of H and OH. I know they will be added on the same side (syn), but since there is a cyclic ring involved, do I represent it with the molecule on the left or right? Or are they both wrong?
Title: Re: Representing product of alkene hydration
Post by: kriggy on October 21, 2018, 03:23:30 AM
Quote from: owlpower on October 21, 2018, 02:35:17 AM
Here is a hydration reaction. I know that BH3 and OH- is used, so this will be a anti-Markovnikov, syn addition.


You are wrong on this, its indeed a syn addition but it follows the markovnikov rule. Look up the mechanism on wikipedia, its not really an addition of water but first addition of BH3 followed by oxidative cleavage of the boron compound into alcohol

 I think both are correct but I prefer the 1st one because its bit easier to read
Title: Re: Representing product of alkene hydration
Post by: spirochete on October 23, 2018, 02:54:01 PM
They should both be correct, but it would be good to understand here that you can't really observe syn addition in that product, because only one chirality center is formed. So it's a little weird to draw the H as a wedge. Syn and anti addition would give the same product in that molecule, due to free single bond rotation.