What is the correct order of basicity among the following compounds? (I) Ref. images (II) CH3−CH2−NH2 (III) (CH3)2 (IV) CH3−O||C−NH2

CH3−NH||C−NH2 + H+ ⇌ CH3−NH2+||C−NH2 ⇌ CH3−+NH2||C−NH2 ⇌ CH3−NH2|C=+NH2
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° amines (III) are more basic than 1° 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.