Wednesday, November 7, 2007 - 2:35 PM
410f

Quantitative Analysis Of H-Bonding Interactions: Relation To Crystal Shape And Size

Charles Acquah1, Luke E. K. Achenie2, Arunprakash T. Karunanithi3, Shanthakumar Sithambaram4, Steven Suib5, and Jose Gascon4. (1) Chemical Engineering, University of Connecticut, Storrs, CT 06269, (2) Department of Chemical Engineering, Virginia Polytechnic Institute and State University, Randolph Hall 133, Blacksburg, VA 24061, (3) U.S. Environmental Protection Agency, 26 W. Martin Luther King Drive, Cincinnati, OH 45268, (4) Department of Chemistry, University of Connecticut, Storrs, CT 06269, (5) Department of Chemistry, Chemical Engineering and Institute of Material Science, University of Connecticut, Storrs, CT 06269

This study was aimed at exploring the role of hydrogen bonding interaction between crystal and solvent molecules in the determination of crystal morphology. Two different approaches were used. The first approach involved using Fourier Transform Infra-Red (FTIR) spectroscopy analytical experiments to study crystal-solvent interactions. The FTIR spectrum of different solvents ranging from non-polar to highly polar are examined for differences in spectra shift on addition of a small but fixed amount of solute. Solutes used in this study were succinic acid, adipic acid and ibuprofen. The differences in spectra shift was used as a measure of the hydrogen bonding interaction. The second approach employs molecular dynamics (MD) to investigate crystal-solvent interactions which are mainly controlled by interfacial tension between the two phases. Preliminary results show that hydrogen bonding (H-bonding) interaction in some solvents (e.g. methanol, ethanol) was intermolecular. However, for some other group of solvents (e.g. ethylene glycol, propylene glycol and glycerol), which are characteristically viscous, bonding tended to be intramolecular and this greatly limits their intermolecular interaction. These solvents therefore behave like “non-polar” solvents. This observation was consistent for both the FTIR and MD approaches. In the context of crystal morphology, we expect these group of solvents to exhibit morphology somewhat similar to that of the morphology of crystals grown from non-polar solvents. Insights gained from this work provides useful information for designing and selecting solvents for use in pharmaceutical crystallization processes.