Question

Aniline is less basic than ethylamine

Answer 1

Aniline is less basic due to lesser availability of lone pair of electrons.

1.)Due to resonance effect which delocalises the lone pair all over the benzene ring.

2.)There is also a second reason: Lesser stability of conjugate acid than aniline:

C6H5NH2 + H2O : C6H5NH3

anilinium ion is less stable than aniline,hence equilibrium shifts towards the left.

Answer 2

$\huge\textcolor{orange}{\texttt{Answer :-}}$

The strength of a base or an alkaline solution is determined by the pK$_b$ value. The lower the pKb value, the stronger the base. In the case of methylamine and aniline, aniline has more pK$_b$ value. Hence, aniline is less basic than methylamine. This happens because :

In aniline, the lone pair of electrons on N atom is delocalized over the benzene ring. As a result, electron density on the nitrogen decreases.

On the other hand, in $CH_3NH_2$, + I effect of $CH_3$ group increases the electron density on N atom.

Therefore, aniline is less basic than methylamine and hence pK$_b$ of aniline is higher than that of methylamine and aniline is less basic than methylamine.