Question

Arrange the following in increasing order of their basic strength : $CH _{3} NH _{2}( I ),\left( CH _{3}\right)_{2} NH ( II ),\left( CH _{3}\right)_{3} N ( III )$, $C _{6} H _{5} CH _{2} NH _{2} (IV)$

• A. IV < III < II < I
• B. IV < III < I < II
• C. I < II < III < IV
• D. IV < III < I = II

Answer 1

Answer: (B)

IV < III < I < II

Answer 2

Basic character depends upon the availability of lone pair of electrons over nitrogen for donation. Presence of electrons releasing group like $- CH _{3}$ increases the electron density over nitrogen, thus lone pair of nitrogen are more available for donation. Hence, basic character increases.
But $3^{\circ}$ methyl amines are less basic as compared to $2^{\circ}$ and $1^{\circ}$ amines due to steric hindrance. Thus, the order of basic strength of the given compounds is