Question

Arrange in increasing order of basicity.

$HC\equiv C^{-},{CH}_{3}CH={CH}^{-},{{CH}_3{CH}_2}^{-}$

• A. $HC\equiv C^{-}>{CH}_{3}CH={CH}^{-}<{{CH}_3{CH}_2}^{-}$
• B. $HC\equiv C^{-}>{CH}_{3}CH={CH}^{-}>{{CH}_3{CH}_2}^{-}$
• C. $HC\equiv C^{-}<{CH}_{3}CH={CH}^{-}<{{CH}_3{CH}_2}^{-}$
• D. $HC\equiv C^{-}={CH}_{3}CH={CH}^{-}={{CH}_3{CH}_2}^{-}$

Answer 1

Answer: (C)

$HC\equiv C^{-}<{CH}_{3}CH={CH}^{-}<{{CH}_3{CH}_2}^{-}$

Acetylene is the strongest acid and ethane is the weakest acid.
Weakest acid (ethane) has strongest conjugate base $\left({{CH}_3{CH}_2}^{-}\right)$ and strongest acid (acetylene) has weakest conjugate base $HC\equiv C^{-}$.
Hence, the increasing order of the base strength is $HC\equiv C^{-}<{CH}_{3}CH={CH}^{-}<{{CH}_3{CH}_2}^{-}$.