Weaning students off of "known" chemistry: A paradigm for the senior organic laboratory course

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  • 1. Weaning students off of “known” chemistry: A paradigm for the senior organic laboratory course Prof. Thomas Gardner Department of Chemistry Muhlenberg College Allentown, PA 18104 [email_address]
  • 2. Objectives of the Senior Organic Laboratory Course
    • Learn to obtain guidance from the literature and adapt procedures to unknown target compounds: train scientists, not just technicians
    • Become familiar with the practical aspects of synthesis design
    • Transfer concepts from synthesis research into the teaching lab
    • Break the habit of “characterization by comparison”
    • Adopt a journal-style approach to lab reports
    • Enhance critical thinking in evaluation of known procedures and development of new procedures
    • Introduce new and advanced laboratory, characterization and computation techniques
  • 3. Context of the project: 1,5-diphenylanthracene
    • prochiral “playing card” symmetry
  • 4. Four project stages
    • Four-step synthesis of 1,5-diphenylanthracene (DPA) 6 weeks
    • Preparation of dienophiles: dimethyl acetylenedicarboxylate (DMAD) and fumaronitrile 3 weeks
    • Diels-Alder reactions 2 weeks
    • Independent projects with DPA or one of the Diels-Alder products 3 weeks
    • Class meets three hours on Monday, and one hour on Wednesday
  • 5. Reduction of DCAQ
    • Techniques:
    • Soxhlet extraction (optional)
    • 2-D NMR
  • 6. A B D C
  • 7.  
  • 8. Phenyl coupling
    • Techniques:
    • Inert atmosphere (glove bag, cannula, prep of PhMgBr in THF under N 2 )
    Based on synthesis of 1,8-diphenylanthracene by House, H. O.; Hrabie, J. A.; VanDerveer, D. J. Org. Chem. 1986 , 51 , 921-929.
  • 9.  
  • 10.  
  • 11. Dienophiles: DMAD & fumaronitrile
    • Techniques:
    • Vacuum distillation, Schlenk line
    • Sublimation
    • GC-MS
  • 12. DPA + DMAD
    • Techniques:
    • Inert atmosphere (?)
    • Chiral shift agents
  • 13.  
  • 14. DPA + fumaronitrile exo pair endo pair
  • 15.
    • Before recrystallization
    After recrystallization
  • 16. Student projects
      • saponification of ester and resolution of acid pair
      • reaction of ester with esterase enzymes ( Candida antarctica and pig liver esterase)
      • dimerization of diphenylanthracene
      • Vilsmeier to create 9-carboxaldehyde
      • reaction with chiral dimenthyl acetylenedicarboxylate and dimenthyl fumarate
      • free radical dehydrogenation of fumaronitrile product
  • 17. What would be done differently next time?
    • More time spent on project
    • Pre-synthesize 1,5-dichloroanthracene
    • Skip dienophile syntheses, or overlap with earlier procedures
  • 18. Student Feedback
    • “ I really enjoyed the style and the material we covered. At times it was frustrating working with novel compounds but we all benefited from this experience.”
    • “ We could have used more readings”
    • “ We should spend 2-3 more weeks on the independent projects.”
    • “ We were all sometimes guilty of getting into lab and working without fully thinking through or questioning what we were doing.”
  • 19. Conclusion
    • Research results can provide a useful means for bridging the student experience into the unknown, and prompt them to think independently and critically about synthesis procedures in the lab.
  • 20. Acknowledgements
    • Melissa Betof
    • Danielle Falcone
    • and the rest…
  • 21.