The main product formed when ethyl benzene reacts with chlorine in the presence of UV light is

1-Chloro-1-phenyl ethane

The correct answer is option 1. 1-Chloro-1-phenyl ethane.

When chlorination of ethylbenzene is carried out in presence of heat or light, 1-chloro-1-phenylethane is obtained as the major product. In this reaction, chlorine enters the alkyl side chain and aromatic benzene ring is not affected.

When chlorination of ethylbenzene is carried out in the presence of iron or ferric chloride catalyst, the aromatic ring is substituted to form a mixture of o-chloroethyl benzene and p o-chloroethyl benzene. This is because the ethyl group is an ortho para directing group. Also, ethyl groups are activating in electrophilic aromatic substitution reactions.