ms to distinguish isomers mass spectr ometr y summar...
TRANSCRIPT
1
Mass Spectrometry - molecular ionization
MOLECULE
electron beam
e-
MOLECULE
2
Mass Spectrometer
3
MS to distinguish isomers
m/z = 84
+ CH3
m/z = 79
+ CH2CH3
m/z = 84 m/z = 56
4
Mass Spectrometry Summary
Mass of the molecule
Molecular Formula
Fragments - Most stable carbocations (and radicals)
Can give idea about how the molecule was connected
Can often identify constitutional isomers
5
Electromagnetic Spectrum
6
Energy of a photon
E = h!
E = hc/!
= c! "x
7
Molecular Vibrations
8
IR Spectrometer
9
Typical IR Spectra
= 1!
"10
Typical Ranges for common functional groups
4000 3500 3000 2500 2000 1500 1000 500
wavenumber, cm-1
O H
C H
C H
C H
C C
C N
C O
Strong
StrongBroad
11
Octane IR Spectrum
C H 2850 - 2960 cm-1
12
Octene IR Spectrum
C H 3020 - 3100 cm-1
13
Heptyne IR Spectrum
C H 3300 cm-1 (strong) C 2100-2260 cm-1C
14
Ethanol IR Spectrum
O H 3400-3650 cm-1 (strong, broad)
15
Butyraldehyde IR Spectrum
O
H
O 1670-1780 cm-1 (strong)C
16
Ethyl Acetate IR
O
O
O 1670-1780 cm-1 (strong)C
17
Benzonitrile IR
CN
N 2100-2260 cm-1C
18
Typical Ranges for common functional groups
4000 3500 3000 2500 2000 1500 1000 500
wavenumber, cm-1
O H
C H
C H
C H
C C
C N
C O
Strong
StrongBroad
19
Functional Group Stretches
C H
C H
C H
O H
CC
NC
C O
Functional Group
Wavenumber
Range (cm-1)
Absorption Strength
2850-2960 medium-strong
3020-3100 medium
3300 strong
3400-3650 broad-strong
2100-2260 medium
1680-1750 strong
notes
below 3000
above 3000
above 3000
Infrared Stretching Absorptions