Question

What is the correct order of basicity among the following compounds ?

• A. II > I > III > IV
• B. I > II > III > IV
• C. III > I > II > IV
• D. I > III > II > IV

Answer 1

Answer: (D)

I > III > II > IV

Answer 2

The conjugate acid formed by addition of a proton to I is stabilised by two equivalent resonance structures and hence, compound I is the most basic. Further 2$^{\circ}$ amines (III) are more basic than 1$^{\circ}$ amines (II) while amides (IV) are least basic due to delocalisation of lone pair of electrons of N over the CO group. Thus, the order is : I > III > II > IV.