Q.
Under certain conditions an alkyl halide reacts with base to give an alkene and HCl [Elimination Reaction] for example
$ R - CH_2 - CH2 - Cl ® R - CH = CH_2 + HCl$
The extent of these reactions depends on the structure of alkyl halides (e.g. primary, secondary or tertiary). The relative extent to which such reactions take place is in the order (of haloalkanes) :
Haloalkanes and Haloarenes
Solution: