An Improved Resolution of (±)-1-Phenylethylamine

Stereochemistry and polarimetry are often introduced in organic chemistry laboratory with the resolution of (±)-1-phenylethylamine using (+)-tartaric acid as the resolving agent. However, there are significant drawbacks to the commonly used experimental procedure. Isolating the resolved (–)-1-phenylethylamine from solution is problematic as it is viscous, reacts with the atmospheric carbon dioxide, and stinks. Furthermore, the use of a full equivalent of (+)-tartaric acid resolving agent requires a large volume of solvent. We have developed two practical improvements to this experiment: (1) By keeping the resolved amine in solution and measuring its concentration with refractometry, the isolation of the problematic neat amine is avoided; and (2) By decreasing the amount of resolving agent, the resolution can be accomplished using appreciably less solvent and generating less chemical waste, thus making the experiment greener.