11.3 Anti-Markovnikov hydrobromination
11.3.1 Of an alkene
Anti-Markovnikov halides can also be synthesized. When peroxide is added to the reaction of HBr and an alkene, a different mechanism occurs than the one we saw previously. When peroxide is added, a free radical mechanism occurs. The first step of this mechanism is that the peroxide breaks apart to form free radicals.
The oxygen free radicals react with H-Br to make bromine radicals.
The bromine radical can attack one of two ways. We’ll look at both possibilities and choose the one with the more stable intermediate. Remember, we ALWAYS do this. But, in the end, we will make more of the anti-Markovnikov product.
11.3.2 Of an alkyne
If HBr and peroxide are reacted with an alkyne, a free radical reaction occurs giving anti-Markovnikov addition of HBr.
The reaction usually does not occur again. It tends to stop at the double bond.
2. Draw the products of the following reactions.
