Ianiant [Jan 22 07:49 PM]: Do you want to learn about both Markovnikov and anti-Markovnikov hydrohalogenation of alkenes?
~DoodleNoodle~ [Jan 22 07:51 PM]: Sure thing, Ianiant
Ianiant [Jan 22 07:54 PM]: Markovnikov hydrohalogenation occurs when a hydrogen-halogen compound is added to an alkene, and ionic mechanisms cause the hydrogen to be added to the less-substituted carbocation while the halogen is added to the more-substituted carbocation.
Ianiant [Jan 22 07:56 PM]: anti-Markovnikov hydrohalogenation works similarly, but only with HBr and only in the presence of even a minute amount of peroxide. The peroxide breaks apart to form radicals, and one of these radicals takes the hydrogen from bromine to form a bromine radical.
Ianiant [Jan 22 07:57 PM]: The bromine radical then interacts with the alkene's π-bond, which is an area of electron density, which causes the bromine to be placed at the less-substituted carbon radical so that the only carbon radical in the molecule is in the most substituted area possible.
Ianiant [Jan 22 07:58 PM]: Then, another HBr breaks apart to form radicals. The hydrogen radical joins with the carbon radical to make a stable molecule and an anti-Markovnikov product.
Ianiant [Jan 22 07:59 PM]: Oh, I forgot to mention, the peroxide needs to be in the presence of light energy or heat to break apart into radicals.
Ianiant [Jan 22 08:03 PM]: Oh, and the remaining bromine radical causes a chain reaction of hydrohalogenation.
