Question

Arrange the following compounds in the increasing order of their basic strength in the gaseous phase:
C$_6$H$_5$NH$_2$, (C$_2$H$_5$)$_3$N, (C$_2$H$_5$)$_2$NH

Hint:

Aromatic groups withdraw electron density, reducing basicity, while alkyl groups donate electron density, increasing basicity.

Answer 1

Basic strength of amines is influenced by the electron-donating or electron-withdrawing nature of their substituents. Alkyl groups are electron-donating, which increases the basicity of the amine, whereas an aromatic group (like in aniline) is electron-withdrawing and decreases the basicity. Order of basicity in the gaseous phase: \(C_6H_5NH_2\) < \((C_2H_5)_2NH\) < \((C_2H_5)_3N\) - C$_6$H$_5$NH$_2$ (Aniline) has the lowest basicity because the phenyl group withdraws electron density from the nitrogen.
- (C$_2$H$_5$)$_2$NH (Diethylamine) has higher basicity because two ethyl groups donate electron density to the nitrogen.
- (C$_2$H$_5$)$_3$N (Triethylamine) has the highest basicity due to the three electron-donating ethyl groups.