Question

The best leaving group is :

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

Since more information is not given, we can assume a general case. For all the four options, we have either a lack or the presence of various substituents at the position para to sulphonate group. For the leaving group to be more effective, the charge on the sulphonate group should be better spread out. Hence, more the electron-withdrawing nature of the para group attached, greater is the stabilization of negative charge. Hence the answer. The nitro group is much more electron withdrawing than any other group. Bromine withdraws electrons via the inductive effect but it may be able to weakly donate electrons into the benzene ring via conjugation. The methyl group slightly activates the ring via hyperconjugation.