A) IV < III < II < I
B) IV < III < I < II
C) I < II < III < IV
D) IV < III < I = II
Correct Answer: B
Solution :
Basic character depends upon the availability of lone pair of electrons over nitrogen for donation. Presence of electrons releasing group like \[-C{{H}_{3}}\] increases the electron density over nitrogen, thus lone pair of nitrogen are more available for donation. Hence, basic character increases. But \[{{3}^{o}}\] methyl amines are less basic as compared to \[{{2}^{o}}\] and \[{{1}^{o}}\] amines due to steric hindrance. Thus, the order of basic strength of the given compounds is \[\underset{\begin{smallmatrix} (IV) \\ (because\text{ }of\text{ }electron\text{ }with \\ drawing\text{ }phenyl\text{ }group) \end{smallmatrix}}{\mathop{{{C}_{6}}{{H}_{5}}C{{H}_{2}}N{{H}_{2}}}}\,\] \[\underset{\underset{(III)}{\mathop{{{\text{3}}^{o}}\text{ }amine}}\,}{\mathop{<{{(C{{H}_{3}})}_{3}}N}}\,\] \[\underset{\underset{(I)}{\mathop{{{1}^{o}}a\operatorname{mine}}}\,}{\mathop{<C{{H}_{3}}N{{H}_{2}}}}\,\underset{\underset{(III)}{\mathop{{{3}^{o}}a\min e}}\,}{\mathop{<{{(C{{H}_{3}})}_{2}}NH}}\,\]
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