Write-up procedure: 1. Determine molecular formula from elemental analysis.

1. Write-up procedure: 1. Determine molecular formula from elemental analysis. 2. Determine elements of unsaturation from molecular weight [EOU=1/2(2C+2-H)] 3. Show all work 4. Label important stretches in the NMR and IR 5. Determine the structure Experiment 1 post lab due in two weeks (week of Feb 6th-10th)

2. Example 1: MW: 88.1; BP: 73-76 °C/12 mmHg(lit.), Elemental Composition: C 54.53% H 9.15%

4. Example 2: MW: 169.22; BP: 302 oC, MP 52-54 oC; Elemental Composition: C 85.17% H 6.55% N 8.28%

6. NMR Signals • The number of signals shows how many different kinds of protons are present. • The location of the signals shows how shielded or deshielded the proton is. • The intensity of the signal shows the number of protons of that type. • Signal splitting shows the number of protons on adjacent atoms.

7. The NMR Graph

8. Tetramethylsilane • TMS is added to the sample. • Since silicon is less electronegative than carbon, TMS protons are highly shielded. Signal defined as zero. • Organic protons absorb downfield (to the left) of the TMS signal. => Chapter 13

9. Chemical Shift • Measured in parts per million. • Ratio of shift downfield from TMS (Hz) to total spectrometer frequency (Hz). • Same value for 60, 100, or 300 MHz machine. • Called the delta scale. => Chapter 13

10. Delta Scale Chapter 13 =>

11. Location of Signals • More electronegative atoms deshield more and give larger shift values. • Effect decreases with distance. • Additional electronegative atoms cause increase in chemical shift. => Chapter 13

12. Typical Values Chapter 13 =>

13. C5H10O

16. Example 3: MW: 108.14; BP: 202 oC, MP 32-34 oC; Elemental Composition: C 77.75% H 7.46%

17. Example 4: MW: 108.14; BP: 203 oC, MP 8-10 oC; Elemental Composition: C 77.75% H 7.46%