Question

Which statement is true about $S_{N}2$ mechanism?

• A. The rate of reaction increases on increasing the strength of nucleophile.
• B. The reaction is faster in polar aprotic solvents.
• C. The rate of reaction increases as the leaving group ability increases.
• D. All of the above.

Answer 1

The correct option is D All of the above.

Nucleophile is involved in rate determining step of $S_{N}2$ mechanism.
Hence, stronger the nucleophile, faster the $S_{N}2$ reaction.
Polar aprotic solvent favours $S_{N}2$ reaction because polar aprotic solvent is unable to solvate the nucleophile.
So, the nucleophilicity of a nucleophile does not decrease in such solvent.
A better leaving group lowers the activation energy, thus, increasing the rate of $S_{N}2$ reaction.

Polar aprotic solvent