The correct order of basicity of the following compounds is

Options

A. `1lt2lt3lt4`
B. `1lt2lt4lt3`
C. `2 lt1lt3lt4`
D. `4lt3lt2lt1`

Answer

C

Explanation

The conjugate acids obtained by addition of proton to amine (4) is resonance stabilized by three equivalent structures (I, II and III) while that obtained from amine (3) is resonance stabilized by two equivalent structures (IV and V).

Therefore, amine (4) is more basic than amine (3). In amine (1), lone pair of electrons is present on a `sp^(3)` hybridized N while in amine (2), it is present on a `sp^(2)` hybridised N. Since a `sp^(2)` hybridised N has more s-character (more electronegative) than a `sp^(2)` hybridised N, therefore, amine (2) has lesser tendency to donate its electron pair than amine (1). In other words, amine (2) is less basic than amine (1). Combining these trends, the basicity of four amines increases as:
`(2) lt (1) lt (3) lt (4)`