Question

Which of the following is the most stable carbanion?

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

The formation of C - H bond in acetylene involves sp-hybridised carbon atom. Since s-electrons are closer to the nucleus than p electrons, sp hybrid orbitals are more electronegative.

%s-character $\propto$ Electronegativity $\propto$ Stability of carbanion.
(a) has $sp$ carbon which is more electronegative and stabilise the carbanion more.
(b) and (d) has $s{p}^2$ carbon which has less s character than $sp$ so it is less stable.
Compound (c) has $s{p}^3$ carbon which has least s character. Thus, it is least stabilised.