Chemistry - GOC Question with Solution | TestHub

Compound (1) contains a cyclic guanidine unit (the central carbon bonded to three nitrogens) : protonation gives a cation whose charge is delocalised over all three nitrogens, making it a very strong base. Compound (4) contains a cyclic amidine (DBU-type) : the charge is shared by two nitrogens, so it is strong but below the guanidine. Compound (2) is a bicyclic diamine with two ordinary secondary amines - normal amine basicity, below the amidine. Compound (3) is a bis-lactam : both nitrogens are amides with their lone pairs delocalised onto the carbonyls, making it by far the weakest. Hence 1 $>$ 4 $>$ 2 $>$ 3.