Review on the heterogeneous equilibria between condensed phases in binary systems of enantiomers

In contrast to what is often expressed in the literature, reversible and irreversible solid(s)-solid(s) transitions in binary system of non-racemizable enantiomers are not always referred to as polymorphism. Order-disorder phenomena, miscibility gaps with critical temperatures and transitions in which three-phases or even four-phases are involved can also occur. In the case of reversibility, three-phase invariants such as eutectoid or peritectoid corresponding to the reversible formation or decomposition of racemic compounds are described. The heterogeneous equilibria are reviewed with or without miscibility in the solid state. Several four-phase invariants and order-disorder transitions are predicted.