Question

Question: Explain why the addition of HBr to alkenes A and C is regioselective, forming addition products B and D, respectively.

Short answer

Answer

Step-by-step solution

Regioselectivity

The regioselectivity term is used when a compound has many locations to form products. But the attacking reagent attacks a particular location and forms a regioselective product.

Explanation for A

When alkene A is treated with HBr, Br can attack at two places, but it prefers the carbon adjacent to the methoxy group as it is more electrophilic. As a result, it forms a regioselective product.

Explanation for B

When alkene B is treated with HBr, Br can attack at two places, but it prefers the carbon away from the carbonyl group as it is more electrophilic. As a result, it forms a regioselective product.

Regioselective product obtained from B