posted on 2023-01-04, 14:36authored byKinga Roszak, Andrzej Katrusiak
High-pressure recrystallization could be the cheapest
clean method
of resolving enantiomers from the racemates defying Wallach’s
rule. We have investigated the effect of pressure on sodium tartrate
monohydrate (NaTa·H2O), a notorious exception from
Wallach’s rule: both racemic polymorphs α-dl-NaTa·H2O and β-dl-NaTa·H2O are less dense than the enantiomers. According to the mobile-equilibrium
principle, such high-density enantiomorphs should spontaneously separate
under high pressures. The pressure dependence of the Gibbs free energy
explains the preferential crystallization of mixed enantiomers of
NaTa·H2O.