ABSTRACT
Stereochemistry is a topic that can send even the most able into a blind panic! However, an appreciation of stereochemical problems cannot be avoided, since they pervade all of chemistry. Once a few basic principles are mastered, the student has powerful tools with which to approach many important areas of chemistry, including stereoselective synthesis, a major challenge in organic chemistry. In dilute alkali, the intramolecular reaction is faster and an a-lactone is formed with inversion of stereochemistry. This intermediate subsequently reacts with hydroxide with a second inversion of stereochemistry. In the presence of alkali, the carboxylic acid is deprotonated. There are then two competing nucleophilic reactions that can displace bromine: the intermolecular displacement by hydroxide, or the intramolecular displacement by carboxylate. In very concentrated alkali, the direct SN2 displacement is faster, leading to an inversion of stereochemistry.
