Question

Which of the following is the strongest base?

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

The order of electronegativity of hybridised orbital is
$sp>s{p}^2>s{p}^3$

In compound (a), the nitrogen has $s{p}^2$ hybrisided orbitals thus, it reduce the ability of donating lone pair of electrons.

In compound (b), the lone pair on $N$ involved in delocalisation with the double bond. Thus, the lone pair of electrons are not readily available for protonation.

Comparing (c) and (d), the oxygen atom is more electronegative than sulphur. Thus, oxygen withdraw more electron denstiy than sulphur. Hence, lone pair of electrons on $N$ of compound (d) is readily available for protonation. Therefore, compound (d) is the strongest base.