1. Lecture 23 Quiz 6 Average = 72% (36 out of 50) Mass Spectrometry
This week in lab:
Ch 9 Final Report Due
Synthetic #2 PreLab Due
Next week in lab:
Synthetic #1 Final Report Due

2. Molecular Ions
Molecular Ions = sum of atomic weight(s) of all isotopes of all elements in a molecule. If you had 10,000 atoms of each type:
C: C atoms C atoms
H: H atoms 1 2H atoms
O: O atoms, O atoms, O atoms
N: N atoms N atoms
Cl: Cl atoms Cl atoms (3:1 35Cl:37Cl)
Br: Br atoms Br atoms (1:1 79Br:81Br)

3. Molecular Ions: Cl & Br Compounds - Isotopes
Significant M+2 peak => Cl or Br
Cl is 3 parts 35Cl and 1 part 37Cl
Br is 1:1 79Br and 81Br

4. MS of Chlorobenzene M+ C6H535Cl = m/z 112 C6H537Cl = m/z 114
Note ratio:
m/z 112:114
is 3:1
M + 2

5. MS of Bromobenzene C6H579Br = m/z 156 C6H581Br = m/z 158 M+ = 156
Note ratio:
156:158
1:1

6. Mass Spec Correlation Chart #1
Common fragments ions and/or neutral losses:
15 can only be methyl
17 usually OH
18 always H2O
28 CO or CH2=CH2
29 CH3CH2 or CHO
31 CH3O
35/37 Cl (special isotope pattern too!)
42 CH2=C=O
43 CH3CO or C3H7
45 CH3CH2O or COOH
79/81 Br (special isotope pattern too!)

7. Mass Spec Correlation Chart #2
Weights of common fragments or neutral losses:

8. Lab Guide Problems Problem 15.3
Mass spec shown in class (Figure 15.11)
Account for the peaks at m/z values of 88 (M+) , 73, 70, 59,
and 55.

9. Lab Guide Problems Problem 15.5
Account for the peaks in the mass spectrum of 2-octanone
at m/z values of 129 (M+1), 128 (M+), 113, 85, and 43.

10. Lab Guide Problems Problem 19.13
The most intense peak in the mass spectrum of
2,2-dimethylbutane is at m/z = 57. Propose a structure of
this fragment ion (a.k.a. daughter ion).

11. Nutmeg Oil GC-MS Data
Mass Spectrum of A
M+ at 192
Compound is:

12. Nutmeg Oil GC-MS Data
Mass Spectrum of B
M+ at 208
Compound is: