Question

Arrange the following in the decreasing order of basic strength:
i)Aniline
ii)p-nitroaniline
iii)p-toluidine

• A. i > ii > iii
• B. ii > i > iii
• C. iii > i > ii
• D. iii > ii > i

Answer 1

The correct option is C iii > i > ii

In aniline ($C_6{H}_5-N{H}_2$) lone pair of electrons is in conjugated system with benzene ring thus is less available. In p-nitroaniline ($N{H}_2-C_6{H}_5-N{O}_2$) the nitro group exhibits $-M$ effect which withdraws the electrons and makes it least basic. The $-C{H}_3$ group in $p-toluidine$ is an activating group which releases electrons to the ring and makes it a strong base. Thus the decreasing order of strength is $ii>i>iii$/.