Polymorphism of mixtures of enantiomers: A thermodynamic study of mixturesof D- and L-limonene

The solid-liquid phase behaviour of the system {(1-x) mol L-limonene + x mo l D-limonene} has been studied by means of adiabatic calorimetry. The syste m is polymorphic and the thermodynamic behaviour of mixtures of D- and L-li monene during temperature cycles has been investigated. The thermodynamic b ehaviour can be looked upon as the superposition of two phase diagrams. One phase diagram depicts the equilibrium between liquid and stable solid, and the other the equilibrium between liquid and metastable solid. The stable case corresponds to the formation of a racemic compound. The metastable cas e corresponds to a series of mixed crystals.