SUSTAINABLE SYNTHESIS OF L-PYROGLUTAMIC ACID: AN INTEGRATED ORGANIC SYNTHESIS AND STEREOCHEMISTRY EXPERIMENT

(S)-Pyroglutamic acid is a heterocyclic amino acid derivative which was easily synthesized in undergraduate laboratory through a solvent-free environmentally friendly method involving controlled heating and agitation. This preparation allowed teaching stereochemistry in undergraduate levels, which entails the synthesis of (S)-pyroglutamic acid and the assessment of its optical purity using the simple and rapid technique of melting point measurement, corroborated by polarimetry. The reasons why the solid-state properties of enantiomeric mixtures can differ from those of enantiopure compounds are also discussed, with optical rotation not being the sole distinguishing property.

Keywords:
hands-on chemistry; solid-state chemistry; sustainability; stereochemistry; amino acid