| dc.description.abstract | Racemic species involve racemic conglomerate, racemic compound, or pseudoracemate. Engineering technology data included solubility, form space, phase solubility diagram, and crystal habits of d-, l-, and dl-aspartic acid were collected by initial solvent-screening. The d-, l-, and dl-aspartic acid were all soluble in water. The study determined the crystallization of enantiomers.
The existence of different types of enantiomeric solution phase of aspartic acid in water was discovered. We used freezing point of the solution, and crystallization kinetics to prove that those solution phase were different. The transformation of a conglomerate solution (CS) to a racemic compound solution (RCS) was dependent on both temperature and time. The CS was the solution phase which produced conglomerate crystals, and the RCS was the solution phase which gave a racemic compound. The solution phase transformation of the CS of aspartic acid to the RCS of aspartic acid took 5 h at 45oC to complete. However, the presence of succinic acid dissolved in the aqueous solution of what at 60oC hindered the transformation of the CS of aspartic acid to the RCS of aspartic acid up to 8 h. The succinic acid could stablize the metastable conglomerate generated in water by rapid acid-base reactions and the addition of an antisolvent crystallion with the temperature drop of racemic solution of aspartic acid. The presence of l-aspartic acid seeds could alter the crystallization pathways to produce conglomerate aspartic acid solids. Therefore, crystallization of enantiomers of aspartic acid by preferential crystallization could have been very common and easy to be carried out in a large scale on the primitive earth.
Finally, we used the electrical conductance (1) to prove the existence of different types of molecular interactions in the CS and the RCS of aspartic acid, (2) to study the effects of the seeds of l-aspartic acid in the aqueous solution of racemic aspartic acid, and (3) to monitor the overall kinetics of crystallization from the acetone-water solution. The fundamental kinetic (nucleation and crystal growth) and thermodynamic (Gibbs free energy) parameters were then estimated.
| en_US |