NBS will react with alkenes 1 in aqueous solvents to give bromohydrins 2. The preferred conditions are the portionwise addition of NBS to a solution of the alkene in 50% aqueous DMSO, DME, THF, or tert-butanol at 0 °C. Formation of a bromonium ion and immediate attack by water gives strong Markovnikov addition and anti stereochemical selectivities.
Side reactions include the formation of α-bromoketones and dibromo compounds. These can be minimized by the use of freshly recrystallized NBS.
With the addition of nucleophiles, instead of water, various bifunctional alkanes can be synthesized.