Which of the following compound will most easily be attacked by an electrophile?

Step-by-step solution

Ortho, para directing groups are electron-donating groups; meta directing groups are electron-withdrawing groups. The halide ions, which are electron-withdrawing but ortho, para directing, are the exception. Here - OH group is strong electron donating group. Hence electrophile can easily give electron. - O H group in phenol can release electrons to the ring better than - C H 3 group in toluene. C l atom has electron withdrawing effect which inhibits electrophile attack readily.