IEC 76 |
| Jose E Tabora, James Corry, Richard Osifchin, and John Lepore. Chemical Engineering R&D, Merck & Co., Inc, Rahway, NJ 07065 |
| Direct crystallization is a convenient and generally efficient method to increase the optical purity of partially resolved enantiomers. The rational design of enantiomeric purification by crystallization requires measurement of the solubility of the enantiomers and the racemic mixtures in the process solvent. Enantiomeric system have been classified by the nature of the racemate as, racemic compounds, conglomerates, or solid solutions. In rare cases, however, enantiomers form crystalline addition compounds with an stoichiometry ratio other than 1(S):1(R). These structures are generally known as "anomalous racemates". The solubility and melting point diagrams of each type of enantiomeric system have very characteristic features which have implications on the efficiency of the crystallization to enhance optical purity. This paper will present the discovery of a 1:3 addition compound from the ternary solubility diagram of a chiral alcohol (Merck Compound A). The 1:3 addition compound was isolated and characterized by XRPD and DSC. Additionally, the experimentally measured melting point diagram was found to be in good agreement with the Prigogine-Defay equations. The impact of a non-equimolar addition compound on the achievable optical upgrade through direct crystallization is also discussed.
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Industrial Crystallization (sponsored by Separation Science & Technology Subdivision)
1:45 PM-5:00 PM, Monday, March 24, 2003 Convention Center -- Room 393, Oral
Division of Industrial and Engineering Chemistry |