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CHEM 344Organic Chemistry Lab
June 18th 2008
Spectroscopy of Organic CompoundsLecture 3 –Infrared and Mass Spec
Nick Hill
3
OCPh
H
1703 cm-1
OCEt
HO
1716 cm-1
OCEt
HO
O CEt
OH
2800 - 2600 cm-1
C NPr
2260 cm-1
M + e [M] + 2 e
Molecular Fragments
Molecule
Molecular Ion
EI
Mass Spectrum of methanol CH3OH
32
31
29
15
[CH2OH]+
[CHO]+
[CH3]+
[CH3OH]+.
[M]
Cation stability more important than radical stability
Molecular Ion
A + B
Cation
Radical X
XA + B
Cation
Radical
C8H18MW = 114
8571
57
43
29
114
C6H13+
C5H11+
C4H9+
C3H7+
C2H5+
Mass Spectrum of octane
Mass Spectrum of 2,2,4-trimethylpentane
57
43
Me Me
MeMe
Me
MW=114C8H18Me
Me
Me
C
Me
Me H
Mass Spectrum of 1-butanol
56
OH
MW=74C4H10O
31
43
29
CH2=OH
via loss of H2OCH3CH2
Resonance stabilized
OH
MW = 88C5H12O
Mass Spectrum of 2-methyl-2-butanol
59
55
73
70
4331CH2=OH
OH
OH OH
m/ z = 59
- CH2CH3
- H2O
m/ z = 70
OH OH
m/ z = 73
- CH3
Me
m/ z = 55
- CH3
Mass Spectrum of 2-octanone
OC8H16OMW = 128
113
43
58
O
O
via -cleavage
via -cleavage
O
O
+
CH3+O
m/z = 43
m/z = 113
Molecular ion m/z = 128
-cleavage at a C=O group
Mass Spectrum of 2-octanone
OC8H16OMW = 128
113
43 OH
58
O
O
via -cleavage
via -cleavageMcLafferty rearragement
OH
m/z = 58
+OH
m/z = 128
McLafferty rearrangement of a ketone
1-pentene
O
OH
H OH
OH+
m/z = 60m/z = 88
McLafferty rearrangement of a carboxylic acid
ethene
Mass Spectrum of Benzamide
10577
44
O
O
NH2
O
NH2
C7H7NOMW=121 121
19
Mass Spectrum of Toluene
CH3
MW=92C7H8
92
91Loss of H Benzyl cation???
Tropylium cation m/z = 91
CH3
HH
H
H
HH
H-H
Toluene radical cation m/z = 92
m/z = 91 common to all alkyl benzenes
Mass Spectrum of 3-methyl-1-butanamine
NH2
MW=87C5H13N
30
CH2=NH2
via-cleavage
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