Question

Which one of the following is incorrect statement regarding $S_{N}2$ reaction?

• A. Polar aprotic solvent favour $S_{N}2$ reaction
• B. Strong nucleophiles are preferred
  
• C. Nucleophile is involved in the RDS
• D. Rate depends on R-X only

Answer 1

The correct option is D Rate depends on R-X only

Polar aprotic solvent is unable to solvate the nucleophile thus nucleophilicity of a nucleophile does not decrease in such solvent and hence polar aprotic solvent favours the $S_{N}2$ reaction.
The nucleophile is involved in the RDS in $S_{N}2$ reaction. thus it does affect the rate of $S_{N}2$ reaction.
A strong nucleophile favours $S_{N}2$ reaction.
Rate of the reaction $\propto [R-X{]}^1[Nu{]}^1$ i.e. rate depend on both R-X and nucleophile.
Hence correct option is d.