On the addition of a radical across the spin-paired π bond, it generates a new radical. For instance, the bromine radical interacts with an alkene to produce a radical at a carbon center. The mechanism of the reaction is based on spin conservation, similar to conservation of charge in a chemical reaction. So, a reactant with an unpaired electron forms a product with an unpaired electron. The simplest radical addition reaction is the reduction process, where an electron is added to a spin-paired molecule. One example is Birch reduction, where metals in liquid ammonia generate electrons that react with ketones to form ketyl radicals.