Question

Arrange the following in the increasing order of basic strength :
i) $C_6{H}_{5}N{H}_2$
ii)$C_6{H}_5{N\left({CH}_3\right)}_2$,
iii)$(C_2{H}_5{)}_{2}NH$
iv) ${CH}_3{NH}_2$

• A. i < ii < iii < iv
• B. iii < i < ii < iv
• C. i < iii < ii < iv
• D. i < ii < iv < iii

Answer 1

The correct option is D i < ii < iv < iii

$+I$ effect of alkyl group increases electron density on $-N$ of amine and increases basic strength. Thus $(C_2{H}_5{)}_{2}NH$ is strongest base. In aniline, the lone pair of electrons of $N$ is in delocalization with ring which makes it less available and least basic. Two Methyl substitutions increases basic strength due to its inductive effect but the steric effect also influences it. Therefore the order of basic strength is $iii>iv>ii>i$