Infrared Evaluation of Enantiometric Amount and Application to Racemization at the Interface Between L- and D-Alanine

Amino acids, except for glycine, have two types of molecular structures, L- and D-forms, which are enantiomers. As the L- and D-form molecules have identical chemical and physical properties, they cannot be easily identified by conventional methods. In this study, we found that the amount and the spatial distribution of D-enantiomers in an L-alanine (CH₃CH(COOH)NH₂) matrix in evaporated thin films, which is one of amino acid molecules, can be evaluated quantitatively using an infrared micro spectroscopy with synchrotron radiation. This method was applied to the evaluation of the volume fraction of a racemic component appearing at the interface between L- and D-alanine thin films.