Final answer:
Halogenation of ethylbenzene or propylbenzene under radical conditions typically occurs at the alkyl side-chain, with the hydrogen atoms being replaced by halogen atoms.
Step-by-step explanation:
When ethylbenzene or propylbenzene react under radical conditions, halogenation typically occurs at the side-chain rather than the benzene ring itself. This is because the alkyl groups (ethyl or propyl) are more susceptible to free radical reactions than the benzene ring, which is relatively stable due to electron delocalization.
In the case of ethylbenzene, the hydrogen atoms on the ethyl group are more likely to be replaced by a halogen atom, forming a haloalkane. Similarly, for propylbenzene, the halogenation will preferentially occur on the propyl side chain. These reactions are typically carried out with chlorine (Cl2) or bromine (Br2), and can be initiated by ultraviolet light or high temperatures to produce the respective chlorinated or brominated alkanes.