Arrange the following in increasing order of reactivity towards sulphonation with fuming sulphuric acid.
Benzene, toluene, methoxy benzene, chlorobenzene.

Explanation

Reactivity in electrophilic substitution reactions increases as the electron density in the benzene ring increases. Now since methoxy `(-OCH_(3))` group is a stronger electron-donating group than methyl `(-CH_(3))` group, therefore, methoxybenzene is more reactive than toluene and both are more reactive than benzene. further, since chlorine has -I-effect, therefore, chlorobenzene is less reactive than even benzene. thus, the overall reactivity towards sulphonation increases in the order: chlorobenzeneltbenzenelttolueneltmethoxybenzene.