Question

Consider the given reaction

Which of the following statement(s) is/are correct for above reaction?

• A. It is a concerted reaction
• B. The reaction follows $S_{N}2$ mechanism
• C. The reaction follows $S_{N}1$ mechanism
• D. Configuration of product is (R)

Answer 1

Answer: (A), (B), (D)

Configuration of product is (R)

Since, $NaCN$ is a strong base and the carbocation formed is not much stable. It does not undergo $S_{N}1$ reaction.

In $S_{N}2$ reaction, the nucleophile attacks from the back side and forms a transition state and then the leaving group leaves. It is a single step concerted reaction. The rate of the reaction depends on both reactant and the nucleophile. $S_{N}2$ reaction gives inverse of configuration.
This is a $S_{N}2$ reaction. Reaction configuration 'S' is changed to 'R' in product due to back attack of the nucleophile.
The product is formed by the cleavage of leaving group OTs from the transition state.