Question

Most stable product of the following reaction is:

• A.
• B.
• C.
• D.

Answer 1

The Correct Option is B

To determine the most stable product of the given reaction, we need to consider the reagents and the reaction mechanism involved.

Reaction Overview

1. The first reagent is p\text{-Toluenesulfonyl chloride (TsCl)} in the presence of pyridine. This converts the alcohol into a tosylate, making it a good leaving group.
2. The second step involves \text{NaCN} in \text{DMF}, which is a nucleophilic substitution reaction where the cyanide ion replaces the tosylate group.

Mechanism and Structure

The transformation involves the following steps:

• Formation of Tosylate: The hydroxyl group is converted into a tosylate group, which is an excellent leaving group.
• Nucleophilic Substitution: \text{NaCN} attacks the carbon attached to the tosylate, replacing the tosylate with a cyanide group via an SN2 mechanism.

Consideration for Stability

The stability of the product is determined by the lack of steric and electronic hindrances in the SN2 reaction and the nature of the leaving group.

In this case, the product shown above, where the cyanide group has replaced the original hydroxyl group, is the most stable configuration (considering steric hindrance and the effectiveness of the leaving group).

Conclusion

The most stable product of the reaction is option B, where the aliphatic chain contains a cyanide group, as shown in the image above. This choice is justified by the efficient conversion of alcohol to tosylate and subsequent SN2 substitution.