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• Chromatography (Separations) • Mass Spectrometry • Infrared (IR) Spectroscopy

Analytical Chemistry. • Chromatography (Separations) • Mass Spectrometry • Infrared (IR) Spectroscopy • Nuclear Magnetic Resonance (NMR) Spectroscopy • X-ray Crystallography (visual solid state molecular structure). The Electromagnetic Spectrum.

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• Chromatography (Separations) • Mass Spectrometry • Infrared (IR) Spectroscopy

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  1. Analytical Chemistry • Chromatography (Separations) • Mass Spectrometry • Infrared (IR) Spectroscopy • Nuclear Magnetic Resonance (NMR) Spectroscopy • X-ray Crystallography (visual solid state molecular structure)

  2. The Electromagnetic Spectrum

  3. Nuclear Magnetic Resonance (NMR) Spectroscopy • Identify the environment of hydrogen and carbon atoms • Identify atom connectivity • Identify stereochemical relationships

  4. Nuclear Magnetic Resonance (NMR) Spectroscopy The spin state of a nucleus is affected by an applied magnetic field

  5. Nuclear Magnetic Resonance (NMR) Spectroscopy

  6. Effect of Field Strength

  7. An NMR Spectrometer

  8. 1H NMR of Acetone

  9. 1H NMR of Methyl Acetate

  10. Electron Density Maps

  11. Electron Shielding

  12. Electron Shielding

  13. Common NMR Shifts

  14. Common NMR Shifts

  15. 1H NMR of Methyl Acetate

  16. 1H NMR of Neopentyl Bromide

  17. 1H NMR of Neopentyl Bromide

  18. 1H NMR of Ethyl Acetate 3 Integral ratios 3 2 What are these strange signals?

  19. Proton Coupling Hydrogen nuclei will couple to each other if: • They are not chemically equivalent • They are 2 or 3 bonds apart • Double bonds can cause coupling through 4 bonds

  20. Proton Coupling

  21. Proton Coupling

  22. 1H NMR of Ethyl Acetate 3 3 2

  23. Multiplicity

  24. Determining Hydrogen Atom Relationships The Substitution Test: For any pair of H’s, substitute each separately with an X and compare the two structures. • If the structures are identical – Homotopic (no coupling) • If the structures are enantiomers – Enantiotopic(no coupling) • If the structures are diastereomers – Diastereotopic(coupling is possible)

  25. Determining Hydrogen Atom Relationships

  26. Determining Hydrogen Atom Relationships

  27. Coupling Constants The coupling constant (J) is the distance between two adjacent peaks of a split NMR signal in hertz (Hz) Coupled protons have the same coupling constant

  28. Useful Coupling Constants

  29. Olefin Geometry Through Coupling Constants

  30. A Splitting Diagram for a Doublet of Doublets

  31. A Quartet Vs. A Doublet Of Doublets

  32. Coupling With “Exchangeable” Protons Dry, ultra-pure ethanol Ethanol with trace acid

  33. Four Different (But Similar) Compounds Molecular Ion = 74 [C4H10O]

  34. Unknown #1 9 1

  35. Unknown #2 6 2 1 1

  36. Unknown #3 3 2 1 4

  37. Unknown #4 1 8 1

  38. Putting It All Together - Identifying Unknown Compounds

  39. Putting It All Together - Identifying Unknown Compounds

  40. Putting It All Together - Identifying Unknown Compounds

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