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new slides - chapter 14 ir.pdf
new_slides_-_chapter_14_ir.pdf
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CHEM | 2600 | Organic Chemistry II | exam |O Chemi...
CHEM | 2600 | Organic Chemistry II | exam |O Chemistry 2600 Chapter 14 Infrared Spectroscopy 1 Chapter 1 O Infrared Spectroscopy 2 Infra-red Spectroscopy - Good vibrations C H C H C H C H C H C H ground state vibration IR photon excited state vibration These states are quantized. For absorption to occur, the energy of the photon must exactly match the energy difference between the two states. Energy in s
CHEM | 2600 | Organic Chemistry II ...
CHEM | 2600 | Organic Chemistry II | exam |O Chemistry 2600 Chapter 14 Infrared Spectroscopy 1 Chapter 1 O Infrared Spectroscopy 2 Infra-red Spectroscopy - Good vibrations C H C H C H C H C H C H ground state vibration IR photon excited state vibration These states are quantized. For absorption to occur, the energy of the photon must exactly match the energy difference between the two states. Energy in s
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Chemistry 2600
Chapter 14
Infrared Spectroscopy
1
Chapter 1
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Infrared Spectroscopy
2
Infra-red Spectroscopy
- Good vibrations
C
H
C
H
C
H
C
H
C
H
C
H
ground state
vibration
IR photon
excited state
vibration
These states are quantized.
For absorption to occur, the energy of the photon must
exactly match the energy difference between the two states.
Energy in
sample
Energy out = Energy in less energy absorbed.
IR spectrometers measure the amount of energy transmitted (transmittance) and the
wavelength of light absorbed.
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Infrared Spectroscopy
3
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Infrared Spectroscopy
4
By convention, IR spectra plot transmittance against wavenumber,
ν
where
cm
-1
or wavenumbers
ν
=
λ
1
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Infrared Spectroscopy
5
There are many different type of IR ‘modes’.
To appear in an IR
spectrum,
the mode must involve a dipole change.
symmetric stretch
asymmetric stretch
scissor
rock
wag
twist
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Infrared Spectroscopy
6
ν
=
1
2
π
c
K
μ
μ
=
m
1
m
2
m
1
+ m
2
The masses of the atoms.
K is the force constant.
So, the position of an IR band depends on ...
C
C
C
C
C
C
2150 cm
-1
1650 cm
-1
1200 cm
-1
C
C
H
C
C
C
H
2
C
H
H
H
Just below
3000 cm
-1
Just above
3000 cm
-1
3300cm
-1
the bond strength.
C
H
C
D
C
C
C
O
Just below
3000 cm
-1
2200
1200
1100
and the masses...
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Infrared Spectroscopy
7
ν
4000
3000
2000
1800
−
1650
1650-1500
Fingerprint region
800
O-H broad,
strong
N-H sharper,
less intense
sharp
C
C
C
N
C
O
C
C
C
N
N
O
C—O
oops
Getting the most out of an IR in 30 seconds.
C
H
H
3
C
C
H
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Infrared Spectroscopy - Examples
8
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Infrared Spectroscopy - Examples
9
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Infrared Spectroscopy - Examples
10
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Infrared Spectroscopy - Examples
11
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Infrared Spectroscopy - Examples
12
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Infrared Spectroscopy - Examples
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