Question

An incorrect statement with respect to $S_N1$ and $S_N2$ mechanisms for alkyl halide is

• A. Competing reaction for an $S_N2$ reaction is rearrangement
• B. A weak nucleophile and a protic solvent increases the rate or favours $S_N1$ reaction
• C. A strong nucleophile in an aprotic solvent increases the rate or favours $S_N2$ reaction.
• D. $S_N1$ reactions can be catalysed by some Lewis acids

Answer 1

Answer: (A)

This problem includes concept of $S _{ N } 1$ and $S _{ N } 2$ reaction and factor affecting $S _{ N } 1$ and $S _{ N } 2$ reaction.

During $S _{ N } 2$ reaction of alkyl halide, inversion of configuration takes place instead of rearrangement.

While $S _{ N } 1$ reaction occurs through the formation of carbocation intermediate which is favoured by the presence of lewis acid and aprotic solvent.

Reatrangement of product is also possible in this case.

$CH _{3} X+ KOH (a q) \longrightarrow CH _{3} OH + KX$