Question

Which of the following relation is correct for recativity?
${CH}_{3}CO{O}^{-}$ or ${CH}_3{CH}_2{S}^{-}$ with ${CH}_{3}I$ in ethanol.

• A. ${CH}_3{CH}_2{S}^{-}>{CH}_{3}CO{O}^{-}$
• B. ${CH}_3{CH}_2{S}^{-}<{CH}_{3}CO{O}^{-}$
• C. ${CH}_3{CH}_2{S}^{-}={CH}_{3}CO{O}^{-}$
• D. None of these

Answer 1

The correct option is A ${CH}_3{CH}_2{S}^{-}>{CH}_{3}CO{O}^{-}$

Higher electronegativity means lower nucleophilicity because the role of a nucleophile is to share e-. If the atom is more electronegative it is less willing to share its e- and wants to hold onto them. In the polar protic solvent like ethanol $C{H}_{3}CO{O}^{-}$ participating in Hydrogen bonding, the nucleophile is considerably less reactive than $C{H}_{3}C{H}_2{S}^{-}$ as it interacts less to hydrogen ion. Thus the reaction will be faster for $C{H}_{3}C{H}_2{S}^{-}$ than $C{H}_{3}CO{O}^{-}$.