1. Check your Unknown #3 mass spectrum
Questions of the Day:
Check your Unknown #3 mass spectrum
(or a classmate’s):
Does your Unknown #3 have Br in its molecule structure?
Does your Unknown #3 have Cl in its molecule structure?
Does your Unknown #3 have N in its molecule structure?
Does your Unknown #3 have an aromatic ring?

2. Mass Spectrometry Summary
Molecular weight:
Molecular ion peak M+ ?
odd-numbered (N ...) ?
isotope peaks (Cl, Br)?
Alcohols …
Recognize typical fragments:
H2O, alkyl, acyl, tropylium ion …

3. Weights of common fragments or neutral losses

4. This is the mass spectrum for which compound?
phenetole
Benzoic acid
3-methoxytoluene
Salicylaldehyde
M+ = 122
This is the mass spectrum for which compound? 91 77
107

5. Number of different types of protons
NMR
Basic Information from Proton NMR (Examine your Unknown #3 H-NMR spectrum!)
Number of signals
Number of different types of protons
Chemical shifts
Type of environment for protons
Integration
Ratios of numbers of protons
Splitting of Signals
Information about neighboring protons
Solvent peaks …..

6. Proton NMR Chemical Shifts () For 1H NMR, the scale generally extends from 0-12 ppm (TMS standard)
Simple hydrocarbon protons absorb in the region
Protons on a carbon adjacent to a carbonyl are shifted to 2
(acetone!)
Electronegative atoms (O, halogens) move protons to 3-4
Alkene protons are shifted to 5-6
Aromatic protons to (Amide CONH is also found here)
Aldehydic protons to 10
Most highly shifted protons are generally those of carboxylic acids, with values of 12
Can also be far downfield: phenol OH, enol

7. Proton NMR Chemical Shifts for Common Functional Groups For 1H NMR, the scale generally extends from ppm

8. Proton NMR Common Splitting PatternsB
J’s (Hz)!

9. Practice Proton NMR

10. Practice Proton NMR

12. (Examine your Unknown #3 CMR spectrum!)
13C NMR Chemical Shifts for Common Functional Groups Range ppm (TMS standard) Proton noise-decoupled Integration not useful
(Examine your Unknown #3 CMR spectrum!)
Simple methyl carbons tend to absorb in the region , simple methylene carbons are shifted to 20-65
Electronegative atoms (O, halogens) move attached carbons to
Alkyne carbons are shifted to 70-90,
alkene carbons to ,
aromatic carbons to
Most highly shifted carbons are generally those of carbonyls, with values of

13. 13C NMR Chemical Shifts for Common Functional Groups

14. 13C NMR Practice
How many types of C ? Indicated by how many signals there are in the spectra (solvent peaks ….)
What types of C ? Indicated by the chemical shift of each signal

15. 13C NMR Practice
Symmetry!

16. 13C NMR Practice
How many signals would you expect in the 13C spectrum of
o-xylene
m-xylene
p-xylene?

17. Next time (our last class):
Your questions
Final Exam at 2:10 pm in your Lab!
Exam covers the material of the second half of the semester: “Unknowns”.
Study/ review lab lectures, your labs, practice questions, sample final.
Same rules as for Midterm. No calculator.
Spectral correlation charts will be provided.
How your C336 class grade is calculated ….