question_answer 1)

Arrange the following set of compounds in order of their decreasing relative reactivity with an electrophile,\[{{E}^{+}}\]. (a) Chlorobenzene, 2, 4-dinitrochlorobenzene, p-nitrochlorobenzene (b) Toluene, \[p-{{H}_{3}}C-{{C}_{6}}{{H}_{4}}-N{{O}_{2}},\] \[p-{{O}_{2}}N-{{C}_{6}}{{H}_{4}}-N{{O}_{2}}\]  

Answer:

The typical reactions of benzene are electrophilic substitution reactions. (a) Nitro \[(-N{{O}_{2}})\] group is deactivating group(electron withdrawing) than Cl, therefore more the number of nitro groups, less reactive is the compound. (b) Methyl \[(-C{{H}_{3}})\]group is an activating group(electron donating).