Separation of Enantiomers in a Monolayer of Racemic 3‐Hexadecyl‐oxy‐propane‐1,2‐diol

Monolayers of a racemic mixture and of the pure S enantiomer of 3‐hexadecyloxy‐propane‐1,2‐diol have been characterized by thermodynamic measurements at the air/water interface as well as by fluorescence microscopy. The critical temperature Tc, the limiting molecular area at high pressure and the pressure πc corresponding to the observed main phase transition, derived from the isotherms, slightly depend on chiral purity. Above πc domains with a polygonal shape appear. However, if the domains are compressed shape instabilities occur. While the spirals of the enantiomer turn only in one direction, the spirals arising from one domain of the racemate exhibit opposite handedness. This behavior is explained by a separation of enantiomers on the molecular level in the condensed state of the racemate. A phase diagram is suggested.