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New chiral crystals …

New chiral crystals …. Undergraduate research. Thao Tan Tran, Dan Daranciang, Donald Responte, Crystal Chang, Werner Kaminsky Chemistry Department, University of Washington … and much appreciated helping advice from: Dr Brenden Carlsson, Jason Benedict, …. SUMMARY.

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New chiral crystals …

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  1. New chiral crystals … Undergraduate research Thao Tan Tran, Dan Daranciang, Donald Responte, Crystal Chang, Werner Kaminsky Chemistry Department, University of Washington … and much appreciated helping advice from: Dr Brenden Carlsson, Jason Benedict, …

  2. SUMMARY • Why another new research project • Historically • Constraints ... • The reaction • Failures • Close to success • Outlook

  3. Why another new research project? Problem Material Method Aim Solution

  4. Historically (Undergrad and earlier) telescope at school undergrad lab

  5. Problem How does Faraday Effect depend on composition Material collect existing crystals Method magneto-polarimeter Aim Faraday Effect from Sum-formula Solution Periodic table of rotations, needs density Historically (Cologne)

  6. Periodic Table of molar rotations

  7. “Historically (Oxford)“ Use the small structural variations in a structure introduced during a phase transition to modulate a solid. Study how these changes affect the optical properties. Compare result of calculations with experimental evidence in selected, well-known modelsystems. Debbie Corker, Will Reeves, Pam Thomas, Mike Glazer, James Lewis

  8. “Historically (Seattle)” R-N=C=S + R-NH2 R-NH-C=S-NH-R ca. 100 compounds crystallized similar to above in one year / 18 Publications Douglas West (retired on Longeach, WA)

  9. What are we going to do? Produce crystals of chemically and structurally related molecules to modulate the optical properties. Determine X-ray structures Study these crystals experimentally and computationally.

  10. Problem (Structure-feature relationship) Material (Iso-thiocyanates & chiral ligand) Method (chiro-optics, upol, millipol, tilter OPTACT, DES, Others) Aim (predict crystal features) The research plan

  11. Constraints • No money (and time) • Really no money • Use samples as X-ray teaching aid (free) • “re-use”chemicals (Doug’s left overs) • Undergrads earn credits for efforts Benefits from iso-thiocyanates • Sulfur good for absolute structure • Restricted hydrogen bonds to avoid syrup • Relatively small molecules • High number of chemically related structures

  12. The reaction { 2-Butanol Glyceraldehyde Mannitol not H2O R-N=C=S + H-O-R’ S ║ ca. 60 oC/1h R-N-C-O-R’ R’: chiral, enantiopure! │ H

  13. Failures (1) Reaction when tried in ethanol as common solvent: C9H10ClNOS C9H10BrNOS C9H10ClNOS C9H10N2O3S C9H10N2O3S Substances known*, structures are new *E. Humeres, C Zucco, M. Nunes, N. A. Debacher, R. J. Nunes: Hydrolysis of N-aryl thioncarbamate esters. Modified marcus equation for reactions with assymmetric intrinsic barriers. J Phys. Org. Chem. 2002 15 570-575 (Brazilian/Japanese cooperation)

  14. Failures (2) Reaction when tried in pyridine or DMF as common solvent: C13H10Cl2N2S*DMF C13H12N2S C13H10N4O4S*DMF Substance and structure known: C13H12N2S, rest is new

  15. What happens with H2O (O2?) ? S ║  │ H . . . . . . R-N=C=S + H2OR-N=C=S: R-N-C-O │ H Ө │ H . . O │ H R-NH2 + S=C=O . . . . S ║ . . . . . . . . R-NH2 + :S=C=N-RR-N-C-N-R │ H │ H

  16. R-N=C=S R: Phenyl, 2-chloro-phenyl, 3-chloro-phenyl, 4-chloro-phenyl, 4-bromo-phenyl, 4-nitro-phenyl not among leftovers: methyl-phenyls and methoxy-phenyls

  17. Where is the S=C=O? We do not know, but we got some red crystals … S8 SG: P 2/c And if it doesn’t react at all? C7H4BrNCS SG: P 21 21 2 non-centrosymmetric!

  18. Close to success: reaction works Avoid water and air!! And react with 2-butanol Caveat: because cheap R/S-2-butanol used, no chiral crystals

  19. Outlook • Use enantiopure 2-Butanol • Grow larger crystals • Determine morphology • Measure refractive indices • Calculate refractive indices and higher optical properties • Measure higher optical properties

  20. What do we need? • More chemicals: • Catalyst • Enantiopure 2-Butanol • Methoxy-phenyl and methyl-phenyl iso-thiocyantes • estimated costs ca. $300 • We already have: • enthusiastic undergraduates

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