Question

The product formed when (R)-2-bromopropionic acid is treated with low concentration of hydroxide ion is

• A. predominantly of S configuration
• B. predominantly of R configuration
• C. a racemic mixture
• D. achiral

Hint:

In SN1 reactions, a planar carbocation intermediate leads to a mixture of product configurations, with the inversion leading to the predominant formation of the S configuration.

Answer 1

The Correct Option is A

Step 1: Understanding the reaction.
When (R)-2-bromopropionic acid is treated with a low concentration of hydroxide ions, the reaction proceeds via nucleophilic substitution, where the hydroxide ion attacks the electrophilic carbon attached to the bromine atom.
Step 2: Reaction mechanism.
The substitution follows the SN1 mechanism due to the low concentration of hydroxide ions. In the SN1 mechanism, the leaving group (bromine) departs first, forming a carbocation. This carbocation is planar, allowing the nucleophile (OH\(^-\)) to attack from either the front or the back. However, due to the planar nature of the carbocation intermediate, the attack by OH\(^-\) will result in a mixture of both S and R configurations, with the S configuration being predominant due to the inversion of configuration in the reaction.
Step 3: Conclusion.
The product will be predominantly of the S configuration.
Final Answer: \[ \boxed{\text{Predominantly of S configuration.}} \]