by UV, IR, NMR AND MASS SPECTROMETRIES

1
byUV, IR, NMR AND MASS SPECTROMETRIES
Identification of Compounds
2
Gas Chromatogram of Flavor Compounds
1
11
10
17
3
13
16
15
6
8
9
12
5
7
14
3
Identification of Compound
O
H3C
CH3
H
H
H2
CH3
H
H2
H
CH3
H
4
SPECTROMETRIC IDENTIFICATION
I. Introduction of Spectrometric
Analyses II. Ultra Violet Spectrometry III.
Infrared Spectrometry IV. Nuclear Magnetic
Resonance Spectrometry V. Mass Spectrometry
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I. Introduction of Spectrometric Analyses
The study how the sample interacts with
different wavelength in a given region of
electromagnetic radiation is called spectroscopy
or spectrochemical analysis. The collection of
measurements signals (absorbance) as a function
of electromagnetic radiation is called a spectrum.
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Spectrum of Radiation
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Electromagnetic Spectrum.
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Energy Absorption
The mechanism of absorption energy is different
in the Ultraviolet, Infrared, and Nuclear
Magnetic Resonance regions. However, the
fundamental process is the absorption of certain
amount of energy. The energy required for the
transition from a state of lower energy to a
state of higher energy is directly related to the
frequency of electromagnetic radiation that
causes the transition.
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Spectral Distribution of Radiant Energy
-1
V' Wave number (cm
)
l
Wave length (nm)
V Frequency of Radiation (cycles/sec)
V
1
V'
C
l
-27

(The energy of photon) E V
h
(Planck's Constant 6.62
10
erg - sec)
C
E V
h

h
1 x 107 erg I joule 0.239 calorie Avogadros
number 6.02 x 10 23mol-1
l
l
C V
C
V
l
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Spectral Properties, Application and Interactions
of Electromagnetic Radiation
Gamma ray
Gamma ray emission
Nuclear
X-ray absorption, emission
Electronic (inner shell)
X-ray
Ultra violet
Electronic (outer shell)
UV absorption
Visible
Infrared
IR absorption
Molecular vibration
Molecular rotation
Microwave absorption
Micro-wave
Magnetically induced spin states
Nuclear magnetic resonance
Radio
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Molecular Orbital of Triplet Oxygen
Molecular
Atomic
Atomic
s

p

p

p
p
2Pz
2Py
2Px
2Px
2Py
2Pz
s
Energy
s

2S
2S
s
s

1S
1S
s
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Quantum Numbers and Orbitals
Principal quantum number (n) The average
distance of the electron from the nucleus. 1, 2,
and so on. Azimuthal quantum number (Momentum
quantum number) (l) The shape of the orbital.
1s, 2s, 2p, 3s, 3p, 3d, etc Magnetic quantum
number (Orientational quantum number) (ml) The
orientation of orbital in the space. 2px 2py, 2pz
x, y and z are orientational quantum
number Electron spin quantum number (ms) The
two possible orientation of the electron in a
magnetic field. 1/2 or 1/2
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One S and Three P Orbitals
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The 5 d Orbitals
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II. Ultra Violet Spectrometry
The absorption of ultraviolet radiation by
molecules is dependent upon the electronic
structure of the molecule. So the ultraviolet
spectrum is called electronic spectrum.
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Spectral Properties, Application and Interactions
of Electromagnetic Radiation
Gamma ray
Gamma ray emission
Nuclear
X-ray absorption, emission
Electronic (inner shell)
X-ray
Ultra violet
Electronic (outer shell)
UV absorption
Visible
Infrared
IR absorption
Molecular vibration
Molecular rotation
Microwave absorption
Micro-wave
Magnetically induced spin states
Nuclear magnetic resonance
Radio
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Electronic Excitation
The absorption of light energy by organic
compounds in the visible and ultraviolet region
involves the promotion of electrons in ?, ?, and
n-orbitals from the ground state to higher energy
states . This is also called Energy Transition.
These higher energy states are molecular orbitals
called antibonding.
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Types of Bonds
Antibonding
s

p
Antibonding





p
s
p
s




Energy

p
n
s
n


Nonbonding
n
Bonding
p

Bonding
s

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Electronic Molecular Energy Levels
The higher energy transitions (? ??) occur a
shorter wavelength and the low energy transitions
(???, n ??) occur at longer wavelength.
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Electronic Ground and Excitation States
s
s


s
s
hv
Energy

p
p
p

p
p

p


hv
hv
p
p
p


p
hv
n
n
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Chromophore
Chromophore is a functional group which absorbs a
characteristic ultraviolet or visible region.
210 nm Double Bonds 233 nm Conjugated Diene
268 nm Conjugated Triene 315 nm Conjugated
Tetraene
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III. Infrared Spectrometry
Radiation energy in the infrared region is
absorbed by the organic compound and converted
into energy of molecular vibration. The energy
absorption pattern thus obtained is commonly
referred to as an infrared spectrum which has the
plot of intensity of radiation absorption versus
wavelength of absorption.
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Spectral Properties, Application and Interactions
of Electromagnetic Radiation
Gamma ray
Gamma ray emission
Nuclear
X-ray absorption, emission
Electronic (inner shell)
X-ray
Ultra violet
Electronic (outer shell)
UV absorption
Visible
Infrared
IR absorption
Molecular vibration
Molecular rotation
Microwave absorption
Micro-wave
Magnetically induced spin states
Nuclear magnetic resonance
Radio
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Some Molecular Vibrations
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Atom, Group, and Molecular Rotations
Z
Y
H atom rotation
COOH group rotation
O
H
H
C
X
Molecular rotation
C
O
CH
group rotation
H
H
3
OH group rotation
Center of gravity of the
molecule is at the origin
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Infrared Spectrum
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Infrared Absorption and Functional Groups
3.4 ?m Alkane 6.0 ?m cis-Double Bond 10.3
?m trans-Double Bond 5.8 ?m Carbonyl 3.7
?m Hydroxyl Stretching of Acid Group 2.9
?m Hydroxyl