The Conversion of L-Phenylalanine to (S)-2-Hydroxy-3-phenylpropanoic Acid: A Simple, Visual Example of a Stereospecific SN2 Reaction

We report a simple, inexpensive, visual, and environmentally friendly SN2 reaction appropriate for the second-year organic chemistry laboratory that illustrates stereospecificity, dependence of water solubility on the state of ionization, optical activity, and effect of diastereotopic protons in 1H NMR spectroscopy. The reaction converts readily available L-phenylalanine in a double SN2 reaction to enantiomerically pure (S)-2-hydroxy- 3-phenylpropanoic acid. The optical purity and absolute stereochemistry are determined by the specific rotation of the product. © 2010 The American Chemical Society and Division of Chemical Education, Inc.