halohydriinien

Halohydrins are organic compounds that contain both a halogen atom and a hydroxyl group on adjacent carbon atoms (vicinal halohydrins). They are typically formed by the electrophilic addition of a halogen, such as chlorine or bromine, to an alkene in the presence of water. The reaction proceeds via a halonium ion intermediate, which is opened by water, delivering the halogen and hydroxyl groups in an anti arrangement across the former double bond. In most cases the hydroxyl group ends up on the more substituted carbon and the halogen on the less substituted carbon, though the exact regiochemistry depends on the substrate.

Common halohydrins arise from alkenes treated with Br2/H2O or Cl2/H2O to give bromohydrins or chlorohydrins, respectively. The general product can be represented as R-CH(OH)-CH2-X, with X representing the halogen, but the precise placement reflects the alkene's substitution pattern. Halohydrins are usually liquids or low-melting solids whose properties vary with substituents.

Reactions and applications: halohydrins are versatile intermediates in organic synthesis. They readily undergo base-promoted intramolecular cyclization to form epoxides (three-membered rings) via deprotonation and SN2 displacement of the halide. They can also be transformed into diols or further functionalized, serving as gateways to diverse motifs in natural product synthesis, pharmaceuticals, and polymer chemistry.

Safety and handling: halohydrins can be corrosive and reactive due to the presence of both halogen and hydroxyl functionalities. Proper laboratory precautions and waste handling are required.