Stereoselective crystallization induced by traces of dissolved optically active impurities

Area of Science:

• Crystallization Science
• Chiral Chemistry
• Physical Chemistry

Background:

• Chiral compounds exist as enantiomers, non-superimposable mirror images.
• Understanding enantioselective crystallization is crucial for producing pure chiral compounds.
• Tartrate salts are common chiral compounds used in crystallization studies.

Purpose of the Study:

• To investigate the effect of chiral impurities on the isothermal crystallization of D,L-sodium-ammonium tartrate.
• To determine the critical concentration of seeding agents for preferential crystallization.
• To analyze the relationship between added chiral material and induced optical purity.

Main Methods:

• Isothermal crystallization experiments were performed.
• Varying concentrations of different chiral impurities were admixed.
• Optical purity of deposited crystals was measured.
• Analysis of existing crystallization data was conducted.

Main Results:

• Admixed chiral contaminations led to preferential crystallization of the tartrate isomer with the same handedness.
• The critical concentration for effective seeding agents was found to be 0.1-0.5%.
• 1% optically active excess material induced 1.0-3.6% optical purity in the crystals.

Conclusions:

• Chiral impurities significantly influence enantioselective crystallization.
• The study provides quantitative data on seeding agent effectiveness and optical purity induction.
• Results align with theories on lattice energy differences between enantiomers.