The type of reactive intermediate that is formed in the reaction of propene with n-bromosuccinimide (nbs) to give 3-bromo-1-propene would be an allylic radical. Having NBS as one of the reactants suggests that a free radical bromination would occur between the reactants. In propene, the methyl group would be attacked since the free radical that is being formed would only stabilize by resonance. An allylic radical is a radical that is resonance-stabilized where each of the resonance forms containing unpaired electrons is on an allylic carbon. It can be classified as a primary, secondary or a tertiary allylic radical depending on where is the allylic carbon.
