1. Chem 345: Please Read Three Handouts White Problem Set Yellow Syllabus
It won’t be graded, so it is not due.
Answer key will be posted on canvas.
Yellow Syllabus
Read this.
Pay close attention to exam dates/times for conflicts.
I am serious about the academic misconduct policy.
All of the information about the grading scale is present.
Ivory Powerpoint Slides
We will be going over these the first three days of lecture. Be sure to bring them for the first few days.

2. Why I will lie to you: What students think the answers should be:
The Reality:
Overgeneralizations allow this type of environment:
At the next level, some of the overgeneralizations are removed:

3. Seeing molecules with a different set of eyes
Chem 345 Spectroscopy
Seeing molecules with a different set of eyes

4. Basis of Spectroscopy Higher Energy Empty State ENERGY In ENERGY Out
Some Energy
is Absorbed
Low Energy
Filled State
Detector
Ground State
Excited State

5. Types of Spectroscopy UV-Vis: Electronic transitions
Highly conjugated systems
Eyes, analytical colormetric tests, Beer’s Law
Infrared: Bond stretching
Functional group determination
C=O ~1700 cm-1
C N ~2200 cm-1
O-H, N-H ~ 3300 cm-1
Microwave: Molecular rotation
Microwave ovens
Interstellar molecules (McMahon Research Group)

6. Types of Spectroscopy Nuclear Magnetic Resonance (Radio Frequency)
Nuclear Spin
1H (better known as proton) and 13C most widely used
2H, 6Li, 14N, 15N, 31P, 19F, 29Si are also possibilities
1H is the common isotope of hydrogen (>99%)
13C is not very abundant (~1% of carbon)
Differences in natural abundance between carbon and hydrogen lead to subtle differences in NMR capability
Large magnetic fields generate the different energy states

7. 900 MHz NMR Spectrometer
21.1 Tesla (~ 107 times higher than Earth’s magnetic field)
~ 95 miles of superconducting wire inside

8. Crude NMR Description DE~ Radiowave
700
100
200
600
DE~ Radiowave
400
400
900 MHz instrument at NIH site = approx 20 T
Its got its own spiral staircase!!
Higher magnetic field = greater sep between +1/2 & -1/2 states = more sensitive
INCREASING MAGNETIC FIELD 8

9. 3 Characteristics of NMR Spectra
Chemical Shift (Carbon and Proton)
Type of carbon/protons
Number of inequivalent protons/carbon
Clues about their local environment
Integration (typically just proton)
Number of each type of proton
Clues about their environment
Coupling/Splitting (typically just proton)
Signal shape
Number of protons on adjacent carbons

11. Chemical Shift
TMS
SiMe4
CHCl3
H2O

12. Integration
Area underneath the peaks
proportional to quantity of protons

13. TMS:water 2:1 TMS:water 6:1 TMS:water 1:1 TMS:water 1:6 TMS:water 1:2
The signal for TMS (SiMe4) and the signal for H2O both have the same integration (0.12). What is the ratio of TMS to water in this sample?
TMS:water 2:1
TMS:water 6:1
TMS:water 1:1
TMS:water 1:6
TMS:water 1:2

15. TMS:water 2:1 TMS:water 6:1 TMS:water 1:1 TMS:water 1:6 TMS:water 1:2
The signal for TMS (SiMe4) and the signal for H2O both have the same integration (0.12). What is the ratio of TMS to water in this sample?
TMS:water 2:1
TMS:water 6:1
TMS:water 1:1
TMS:water 1:6
TMS:water 1:2

16. Proton Relationship: Substitution Test
Enantiomers S R
Constitutional
Isomers
Same
Substitution Results Relationship NMR Effect
Same Compound Homotopic Same Chemical Shift
Enantiomer Enantiotopic Same Chemical Shift
Diastereomers Diastereotopic Diff. Chemical Shifts
Constitutional Isomers Heterotopic Diff. Chemical Shifts

17. 2 4 6 8 42 How many types of protons does 2-pentanol have?
(How many signals do you expect?) 2 4 6 8 42

18. Proton Relationship: Substitution Test
Same S R
Diastereomers
When there is a chiral center present, CH2’s are diastereotopic
Substitution Results Relationship NMR Effect
Same Compound Homotopic Same Chemical Shift
Enantiomer Enantiotopic Same Chemical Shift
Diastereomers Diastereotopic Diff. Chemical Shifts
Constitutional Isomers Heterotopic Diff. Chemical Shifts

19. b a 1,4-dimethoxybenzene Ha Hb CHCl3 SiMe4 Downfield Deshielded
Mention CHCl3 in CDCl3
Xylene Shifts 2.3 and 7.0
Upfield
Shielded
CHCl3
SiMe4

20. Upfield
Shielded
Downfield
Deshielded
Just a reminder about CHCl3

21. Aromatic Region
Just a reminder about CHCl3

22. Benzene is 7.34. (CHCl3 appears at 7.2 ppm).
Aromatic Region: ppm
Benzene is (CHCl3 appears at 7.2 ppm).
Strongly deshielded due to induced ring current
and the right hand rule.
External Magnetic Field
Induced Magnetic Field
That shields the interior
of the ring, but deshields
the exterior of the ring.
Induced Ring Current
Just a reminder about CHCl3

23. 18 Annulene