bromohydrin

A bromohydrin is an organic compound containing both a bromine atom and a hydroxyl group on adjacent carbon atoms. They are typically formed by the addition of hypobromous acid (HOBr) to an alkene. This reaction proceeds via a cyclic bromonium ion intermediate, where the bromide ion can then attack from the backside, leading to the formation of the bromohydrin with anti stereochemistry. The hydroxyl group is incorporated at the more substituted carbon due to the carbocation-like character of the intermediate.

Bromohydrins are versatile intermediates in organic synthesis. The hydroxyl group can be readily oxidized or further functionalized, while the bromine atom serves as a good leaving group for nucleophilic substitution reactions. For instance, treatment of a bromohydrin with a base can lead to the formation of an epoxide through an intramolecular nucleophilic substitution. This epoxide formation is a key step in various synthetic pathways.

The synthesis of bromohydrins can be achieved using various reagents, most commonly N-bromosuccinimide (NBS) in the presence of water. Alternatively, molecular bromine in water can also be used, although it can sometimes lead to the formation of dibromoalkanes as byproducts. The regioselectivity and stereochemistry of bromohydrin formation are important considerations for synthetic chemists.