Question

Allylic bromination of an olefin is:
A. Nucleophilic substitution
B. Electrophilic substitution
C. Free radical substitution
D. Electrophilic addition

Answer 1

Bromination refers to any reaction in which bromine (and no other elements) is treated into a molecule. Bromination of an olefins takes place by free radical substitution of $B{r_2}$ that means halogenation of a benzylic position takes place by a free radical substitution reaction.

Complete step by step solution
Free radical substitution takes place, in the presence of sunlight. A free radical is formed during bromination of olefins. Free radical Halogenation refers to the addition of a halogen preceded by free radical substitution reaction. For the allylic bromination a reagent named as NBS is used. NBS refers to N-bromosuccinimide.
There is a different mechanism of bromination also that reaction is called anti-addition. In anti-addition the two substituents are added to opposite sides of a double bond or triple bond that means from the opposite faces. It results in a decrease in bond order and increase in number of substituents.
Bromination reactions are highly crucial in the chemical industry because the versatility of the formed organic bromides makes them suitable building blocks for numerous syntheses. So, due to the use of the toxic and highly reactive molecular bromine these brominations become very challenging and hazardous.
So, option C is correct.

Note
An alkene is named as olefins. Olefins are the unsaturated acyclic hydrocarbons. The word unsaturated means the hydrocarbons which have double bonds. Many of the physical properties of alkenes and alkanes are similar such as they both are colorless, nonpolar, and combustible. The physical state of olefins depends on molecular mass to the corresponding saturated hydrocarbons, the lighter simplest alkenes are gases at room temperature but the linear alkenes with approximately five to sixteen carbons are liquids at room temperature and higher alkenes are waxy solids. As the molecular mass increases the melting point of the liquids.