Match the following.

	Column-I (Reaction)		Column-II (Type of reaction)
a)		p)	Free radical addition
b)		q)	Free radical substitution
c)	${\mathrm{CH}}_4+{\mathrm{Br}}_2\stackrel{\text{ hv }}{⟶}$	r)	Electrophilic addition
d)		s)	Electrophilic substitution

	a	b	c	d
1)	p	q	s	r
2)	q	p	s	r
3)	s	p	q	r
4)	r	p	q	s

The reaction between benzene and chlorine in the presence of either aluminium chloride or iron gives chlorobenzene.It is example of electrophilic substitution.

Under ultraviolet light, three molecules of chlorine add to benzene to produce benzene hexachloride. Benzene hexachloride (C₆H₆Cl₆) is also known as Gammaxane. it is free radical addition.

The reaction between bromine and methane happens in the presence of sunlight. ${\mathrm{CH}}_4+{\mathrm{Br}}_2\to {\mathrm{CH}}_3+\mathrm{HBr}$. The product obtained is bromomethane. One of the hydrogen atom in the methane is replaced by a bromine atom. So this is substitution reaction. During the chain reaction, a new species is generated at the end. The overall process is called as free radical substitution.