Question

Which one of the following carbanions is the least stable?

• A. $C{H}_{3}C{H}_2^{-}$
• B. $HC\equiv C^{-}$
• C. ${(C_6{H}_5)}_3{C}^{-}$
• D. $C{H}_3^{-}$
• E. ${(C{H}_3)}_3{C}^{-}$

Answer 1

Answer: (E)

An organic ion with a pair of available electrons and a negative charge on the central carbon atom is called a carbanion.
Electron attracting group $(-CN,>C=O)$ increases stability and electron releasing group ( $-C{H}_3$ etc) decreases the stability of carbanion. In ${(C{H}_3)}_3{C}^{-},$ three $-C{H}_3$ groups (electron releasing group) are present, so it is least stable.