cis-Bromination of Alkynes without Cationic Intermediates

摘要

The textbook mechanism of the trans-bromination of alkenes and alkynes via a more or less symmetrically bridged bromonium ion does not always apply.Even in the parent system,the reaction of bromine with ethylene,this mechanism is not correct.Highly pure bromine reacts with ethylene in anhydrous dichloromethane only very slowly at room temperature.