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

2. The Electromagnetic Spectrum

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

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

6. Effect of Field Strength

7. An NMR Spectrometer

8. 1 H NMR of Acetone

9. 1 H NMR of Methyl Acetate

10. Electron Density Maps

11. Electron Shielding

13. Common NMR Shifts

15. 1 H NMR of Methyl Acetate

16. 1 H NMR of Neopentyl Bromide

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

19. 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 Proton Coupling

22. 3 2 3 1 H NMR of Ethyl Acetate

23. Multiplicity

24. Determining Hydrogen Atom Relationships 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) The Substitution Test: For any pair of H’s, substitute each separately with an X and compare the two structures.

25. Determining Hydrogen Atom Relationships

27. 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 Coupling Constants

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

33. Molecular Ion = 74 [C 4 H 10 O] Four Different (But Similar) Compounds

34. 1 9 Unknown #1

35. 1 2 1 6 Unknown #2

36. 2 1 3 4 Unknown #3

37. 1 1 8 Unknown #4

38. Putting It All Together - Identifying Unknown Compounds