Question

Which kind of carbanion is the most stable?

a. methyl        b. primary      c. secondary             d. tertiary       e. both a and b

Answer 1

Ans: a. methyl

Reason: Stability of carbanion depends on the inductive effect (transmission of charge through a chain of atoms in a molecule). In simple terms as the C-C+ bonds increaases stability decreases, hence methyl carbanion is most stable as it has no C-C+ bond. Primary is also stable carbanion but methyl carbanion is more stable than primary.

Note: e. both a and b is also right, but when compared methyl is more stable as it has no C-C+ and increase in C-C+ bonds destabilise the carbanions.