CHED 330 |
| Liquid crystals (LCs) are anisotropic organic liquids that have some degree of long-range order typically associated with crystalline solids, yet retain the fluidity of true liquids. The simplest LC is the nematic phase wherein rod-shaped molecules tend to align in the direction of the molecular long axes. In a chiral nematic (N*) LC phase, the molecules take on a supramolecular helical arrangement with the helix axis perpendicular to the molecular long axis. The N* phase can be created by doping small amounts of chiral guest compounds, known as twist agents, into an achiral nematic host. The pitch of the induced helix is inversely proportional to the concentration and helical twisting power (HTP) of the dopant. HTP is an intrinsic property of the dopant and is a measure of its ability to induce twist. It's known that HTP is intimately related to conformation and molecular shape, and theoretical models relating HTP to structure have been formulated for specific conformationally restricted systems such as chiral biaryls. To further investigate the relationship between molecular conformation and HTP, a series of amido-ester and diamide twist agents analogous to the high HTP compound Merck S1011 were synthesized utilizing amino acids as the chirality source. Known for inducing β-turns in polypeptides, (L)-proline was incorporated as shown in Scheme 1. Ab initio calculations of minimum energy conformations of each target were also performed.
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Undergraduate Research Poster Session
2:30 PM-4:30 PM, Monday, August 20, 2007 BCEC -- Exhibit Hall - B2, Poster
Division of Chemical Education |
