Question

Which one of the following(s) is/are incorrect regarding $S_{N}1$ reaction?

• A. Polar aprotic solvents are favourable
• B. Strong nucleophiles are preferred
• C. Nucleophile is involved in the RDS
• D. Rate depends on R-X

Answer 1

Answer: (A), (B), (C)

Nucleophile is involved in the RDS

Polar protic solvent solvates the halide ion formed due to C-X bond breaking. Also it enables the leaving group to leave. Therefore, polar protic solvent favours the $S_{N}1$ reaction.

The nucleophile is not involved in the RDS in $S_{N}1$ reaction. Thus, it does not affect the rate of $S_{N}1$ reaction.
However, a stronger nucleophile may lead to side reactions. So, weak & moderate nucleophiles are preferred.
Rate of the reaction $\propto [R-X{]}^1[Nu{]}^0$
Hence, correct option are (a), (b) and (c).