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 6 th -10 th )

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

Example 2: MW: ; BP: 302 o C, MP o C; Elemental Composition: C 85.17% H 6.55% N 8.28%

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.

The NMR Graph

Chapter 138 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 139 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 1310 Delta Scale =>

Chapter 1311 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 1312 Typical Values =>

C 5 H 10 O

Example 3: MW: ; BP: 202 o C, MP o C; Elemental Composition: C 77.75% H 7.46%

Example 4: MW: ; BP: 203 o C, MP 8-10 o C; Elemental Composition: C 77.75% H 7.46%