Ib Chemistry High Level Content for Spectrum Reading

1. Classical method
Analytical
Techniques
Classical
method
Qualitative analysis
Quatitative analysis
Chemical test
Flame test
Titration
Gravimetric
Instrumental
method
Spectroscopy analysis
Separation analysis
Nuclear Magnetic Resonance Spectroscopy
Atomic Absorption/Emission Spectroscopy
InfraRed /UV Spectroscopy
Mass Spectroscopy
High Performance Liquid Chromatography
Gas Liquid Chromatography
Paper/Thin Layer/Column Chromatography
Analytical Techniques
Quatitative analysis
Qualitative analysis Separation analysis
Flame test
Chemical test
Melting/boiling
point
Gravimetric Titration Distillation Precipitation
Study on Identification, Structural Determination,
Quantification and Separation
Involve Qualitative and Quantitative analysis
• Quantitative – Amt present in sample/mix
• Qualitative – Identity species present in impure sample
• Structural – Determination of structure of molecule
• Separation of mix – Chromatographic Techniques
• Identification of functional gps
• Purity of substances

2. • Spectroscopy measures interaction of molecules with electromagnetic radiation
• Particles (molecule, ion, atom) can interact/absorb a quantum of light
Spectroscopy
Electromagnetic
Radiation
Nuclear spin
High Energy Radiation
Gamma/X ray
Transition of
inner electrons
UV or visible
Transition of outer most
valence electrons
InfraRed
Molecular vibration
Microwave
Molecular rotation
Radiowaves
Low Energy Radiation
Infra Red Spectroscopy Nuclear Magnetic Resonance
Spectroscopy
Ultra Violet
Spectroscopy
Atomic Absorption
Spectroscopy
Velocity of light (c ) = frequency (f) x wavelength (λ) - c = f λ
• All electromagnetic waves travel at speed of light (3.00 x 108
ms-1
)
• Radiation with high ↑ frequency – short ↓ wavelength
• Electromagnetic radiation/photon carry a quantum of energy given by
E = hf

hc
E 
h = plank constant = 6.626 x 10-34
Js
f = frequency
λ = wavelength

3. Electromagnetic Radiation and Spectroscopy
Radiowaves
Nuclear spin
Nuclear Magnetic Resonance
Spectroscopy
• Organic structure determination
• MRI and body scanning
Infrared
Molecular vibration
Infrared Spectroscopy
UV or visible
Transition of outer valence electron
• Organic structure determination
• Functional gp determination
• Measure bond strength
• Measure degree unsaturation in fat
• Measure level of alcohol in breath
Electromagnetic Radiation
UV Spectroscopy Atomic A Spectroscopy
• Quantification of metal ions
• Detection of metal in various samples
Electromagnetic Radiation Interact with Matter (Atoms, Molecules) = Spectroscopy

4. Diatomic molecule of same element DON’T absorb IR
• Symmetrical diatomic bond will not absorb IR
• No change in dipole moment as molecule vibrate
• No absorption of IR
No change in dipole moment
Molecular Vibration
Polar molecule will absorb IR
• H-CI, as bond stretches, distance bet atoms
increases, results in change in dipole moment
• Absorb IR
Condition for molecular vibration to absorb a photon /IR
• Vibration cause oscillation in developing a change in dipole
bet opposite charged centres
• Vibration of bond in HCI cause dipole in bond to oscillate
• Cause a change in dipole moment
Oscillation of bonds
- lead to oscillation of dipole - change in dipole moment
IR absorb - Molecular Vibration – dipole moment change
Change in dipole moment
IR freq = Natural freq for bond – Resonance will happen.
• HCI bond has natural vibrational freq
• IR freq match the vibrational freq in HCI, IR is absorb and molecule excited to vibrational state
• IR absorb by bond will result in greater vibration in amplitude
Diatomic Molecules
Vs
IR frequency
is applied
IR frequency = Natural frequency for bond
↓
IR absorbed and resonance will happen
Dipole change
+
-

5. Diff bond absorb IR radiation at frequency/wavenumber .
IR spectra organic compound with diff functional gps
IR Absorption by diff bonds/functional gps
IR Absorption diff functional gps and fingerprint region
Bond Wavenumber/cm-1
C –CI (Halogenoalkanes) 700-800
C – O (alcohol, ether, ester) 1000 - 1300
C = C (alkene) 1610 - 1680
C = O ( carbonyl) 1680 – 1750
C ≡ C (alkynes) 2070 - 2250
O –H (H bond in COOH) 2500 - 3300
C – H (alkane, alkene) 2840 - 3095
O – H (H bond in alcohol) 3230 - 3550
N – H (amines) 3350 - 3500
C – H stretch
(2840 – 3000)
C – O stretch
(1000-1300)
C = O stretch
(1680 -1740)
O – H stretch
(3230 -3550) C = C stretch
(1610-1680)
Fingerprinting region
• Range (1500- 400cm-1
)
• Specific to each molecule

6. IR spectra organic compound with diff functional gps
IR Absorption by diff bonds/functional gps
Bond Wavenumber/cm-1
C –CI (Halogenoalkanes) 700-800
C – O (alcohol, ether, ester) 1000 - 1300
C = C (alkene) 1610 - 1680
C = O ( carbonyl) 1680 – 1750
C ≡ C (alkynes) 2070 - 2250
O –H (H bond in COOH) 2500 - 3300
C – H (alkane, alkene) 2840 - 3095
O – H (H bond in alcohol) 3230 - 3550
N – H (amines) 3350 - 3500
Fingerprinting region
• Range (1500- 400cm-1
)
• Specific to each molecule
Transmittance
/%
Absorbance
Absorption/Transmittance plotted two ways.
Transmittance Y-axis / wavenumber X-axis.
Absorption on Y-axis / wavenumber on X-axis.
Trans, % (T) and Absorbance (A)
Trans 100% mean IR Absorbance 0%
Trans 0% mean IR Absorbance 100%
wavenumber/cm-1
Transmittance
100%
Absorbance 0%
Transmittance 0%
Absorbance 100%
Infra Red Spectroscopy
• Wavenumber α frequency
• Wavenumber = Reciprocal of wavelength (1/λ) , Unit = cm-1
• Wavenumber = 1/Wavelength = number wave cycles in one cm
IR wavelength from (2500 – 25000)nm → Convert to wavenumber (400 – 4000) cm-1
λ = 2500 nm (convert to cm) → λ = 0.00025 cm → Wavenumber = 1/λ = 1/0.00025 = 4000 cm-1
λ = 25000 nm (convert to cm) → λ = 0.0025 cm → Wavenumber = 1/λ = 1/0.0025 = 400 cm-1
λ low ↓ → Wavenumber, 1/λ is High ↑ → f = c x 1/λ → f is High ↑ → Energy = hf High ↑
wavenumber
bet 400 – 4000cm-1
Higher Wavenumber ↑ = Lower wavelength ↓= Higher ↑ frequency = Greater Energy ↑
Click here khan wavenumber.
Click here khan organic videos.

7. Strength of bond
Single, Double, Triple Bond
Mass of atom
Lighter/Lower Mass atom
• Higher energy frequency for vibration
Stretching Vs Bending
Vibration
IR absorption
frequency
Heavier/Higher Mass atom
• Lower energy/frequency for vibration
Bending Vibration
• Less energy need for resonance
• Lower frequency/wavenumber
Stretching Vibration
• More energy need for resonance
• Higher frequency/wavenumber
Stronger bond
• Higher energy need for resonance
• Higher frequency/wavenumber
Weaker bond
• Lower energy need for resonance
• Lower frequency/wavenumber
IR absorption frequency
Strong bond
Weak bond
C- H = 2840cm-1
C- CI = 600cm-1
C- H stretch = 2840cm-1
C- H bend = 1400cm-1
Bond Bond enthalpy Wavenumber
C –C 348 800-1200
C = C 612 1610-1680
C ≡ C 837 2070-2250
Stretching Vibration
Bending Vibration

8. Molecule to absorb IR
• Vibration within molecule cause a net change in dipole moment
• Frequency of radiation matches vibrational natural frequency of molecule, radiation
will be absorbed, causing a change in amplitude of molecular vibration.
• A permanent dipole not necessary, only a change in dipole moment
• Not all bond absorb IR . For IR absorption, bond must have an electric dipole (bond polarity)
that changes as it vibrates.
• Molecules absorb IR – cause changes in modes of vibration (stretching/bending)
Infrared Spectroscopy and Molecular Vibration
Molecular Vibration
Stretching Mode Bending Mode
Symmetric Stretching
• change in bond length
• bond become shorter/longer
• IR ACTIVE (change in dipole)
• IR INACTIVE (No change in dipole)
Asymmetric Stretching
• change in bond length
• bond become shorter/longer
• IR ACTIVE (change in dipole)
• IR INACTIVE (No change in dipole)
Symmetric Bending
• change in bond angle
• bond angle bigger/smaller
• IR ACTIVE (change in dipole)
• IR INACTIVE (No change in dipole)
Asymmetric Bending
• change in bond angle
• bond angle bigger/smaller
• IR ACTIVE (change in dipole)
• IR INACTIVE (No change in dipole)
wagging twisting rocking scissoring

9. Molecular Vibration
Stretching Mode Bending Mode
Symmetric Stretching
- change in bond length
- bond become short/long
- Change dipole moment
- Absorb IR (active) at 3652
Asymmetric Stretching
- change in bond length
- bond become short/long
- change dipole moment
- Absorb IR (active) at 3756
Symmetric Bending
- change in bond angle
- Angle bigger/smaller
- change dipole moment
- Absorb IR (active) at 1595
Molecular Vibration for H2O (IR Spectrum)
IR spectrum for H2O
Molecular Vibration for SO2 (IR Spectrum)
Molecular Vibration
Stretching Mode
Symmetric Stretching
- change in bond length
- bond become short/long
- Change dipole moment
- Absorb IR (active) at 1150
Asymmetric Stretching
- change in bond length
- bond become short/long
- change dipole moment
- Absorb IR (active) at 1360
IR spectrum for SO2
Click here Spectra database (Ohio State) Click here Spectra database (NIST)

10. Molecular Vibration
Stretching Mode Bending Mode
Symmetric Stretching
- Bond polarity cancel out
- bond become short/long
- NO Change dipole moment
- IR (inactive)
Asymmetric Stretching
- change in bond length
- bond become short/long
- change dipole moment
- Absorb IR (active) at 2349
Symmetric Bending
- change in bond angle
- Angle bigger/smaller
- change dipole moment
- Absorb IR (active) at 667
Molecular Vibration for CO2 (IR Spectrum)
IR spectrum for CO2
Molecular Vibration for SO2 (IR Spectrum)
Molecular Vibration
Stretching Mode
Symmetric Stretching
- change in bond length
- bond become short/long
- Change dipole moment
- Absorb IR (active) at 1150
Asymmetric Stretching
- change in bond length
- bond become short/long
- change dipole moment
- Absorb IR (active) at 1360
IR spectrum for SO2
Click here Spectra database (Ohio State) Click here Spectra database (NIST)

11. Propanal (CH3CH2CHO)
• (2840-3000) → C-H stretch
• (2720) → C-H stretch CHO
• (1680-1740) → C=O stretch
Hex-1-ene CH2=CH(CH2)3CH3
• (2840-3000) → C-H stretch
• (1610-1680) → C = C stretch
• (1200- 1400) → C-H bend
Hex-1-yne CH2≡CH(CH2)3CH3
• (3350) → C ≡ C stretch
• (2840-3000) → C-H stretch
• (1200- 1400) → C-H bend
IR spectra organic compound with diff functional gps
Chloromethane CH3CI
• (2840-3000) → C-H stretch
• (1200-1400) → C-H bend
• (700-800) → C-CI stretch
Halogenoalkane Aldehyde
Alkene Alkyne
C – H stretch
(2840 – 3000)
C – H bend
(1200)
C – CI stretch
(700-800)
C – H stretch CHO
(2720)
C = O stretch
(1680 – 1740)
C – H stretch
(2840 – 3000)
C = C stretch
(1610-1680) C – C bend C ≡ C stretch
(3350)
C – H stretch
(2840 – 3000)
C – H bend
(1200)
CH3CI
CH3CH2CHO
CH2=CH(CH2)3CH3
CH2≡CH(CH2)3CH3
C – H stretch
(2840 – 3000)

12. Methanol (CH3OH)
• (3230-3550) → O-H stretch
• (2840-3000) → C-H stretch
• (1000-1300) → C-O stretch
Ethanol(CH3CH2OH)
• (3230-3550) → O-H stretch
• (2840-3000) → C-H stretch
• (1000-1300) → C-O stretch
Phenol (C6H5OH)
• (3230-3550) → O-H stretch
• (2840-3000) → C-H stretch
• (1400-1500) → C=C aromatic stretch
• (1000-1300) → C-O stretch
Benzoic acid (C6H5COOH)
• (3230-3550) → O-H stretch
• (2840-3000) → C-H stretch
• (1400-1500) → C=C aromatic stretch
• (1000-1300) → C-O stretch
• (1680-1740) → C=O stretch
IR spectra organic compound with diff functional gps
C – O stretch
(1000-1300)
C – H stretch
(2840 – 3000)
O – H stretch
(3230 -3550)
Broad Absorption due to
H bonding bet molecules
Broad Absorption due to
H bonding bet molecules
CH3OH
CH3CH2OH
C – O stretch
(1000-1300)
O – H stretch
(3230 -3550)
C – H stretch
(2840 – 3000)
O – H stretch
(3230 -3550)
C – H stretch
(2840 – 3000)
C – O stretch
(1000-1300)
C = O stretch
(1680 – 1740)
C = C stretch
(1610-1680)
Broad Absorption due to
H bonding bet molecules
O – H stretch
(3230 -3550)
C – H stretch
(2840 – 3000)
C = C stretch
(1610-1680)
C – O stretch
(1000-1300)
Broad Absorption due to
H bonding bet molecules

13. Spectra diff bet Acid and Ester
Ethyl ethanoate (CH3COOCH2CH3)
• (2840-3000) → C-H stretch
• (1680-1740) → C=O stretch
• (1000-1300) → C-O stretch
Methanoic acid (HCOOH)
• (3230-3550) → O-H stretch
• (2840-3000) → C-H stretch
• (1000-1300) → C-O stretch
• (1680-1740) → C=O stretch
Methanoic acid (HCOOH)
• (3230-3550) → O-H stretch
• (2840-3000) → C-H stretch
• (1000-1300) → C-O stretch
• (1680-1740) → C=O stretch
Methanoic acid
Methanoic acid
Spectra diff bet Acid and Alcohol
Methanol (CH3OH)
• (3230-3550) → O-H stretch
• (2840-3000) → C-H stretch
• (1000-1300) → C-O stretch
Ethyl Ethanoate
Methanol
Vs
Vs
O – H stretch
(3230 -3550)
C – H stretch
(2840 – 3000)
C – O stretch
(1000-1300)
C = O stretch
(1680 -1740)
C – H stretch
(2840 – 3000)
C = O stretch
(1680 - 1740) C – O stretch
(1000 - 1300)
O – H stretch
(3230 - 3550)
C – H stretch
(2840 – 3000)
C = O stretch
(1680 - 1740)
C – O stretch
(1000 - 1300)
CH3OH
O – H stretch
(3230 -3550)
C – H stretch
(2840 – 3000)
C – O stretch
(1000-1300)

14. Propan -2-ol CH3CH(OH)CH3 Propanone CH3COCH3
Hexan-1-0l CH3(CH2)4CH2OH Hexan-2-0ne CH3CO(CH2)3CH3
C - H
↓
← C-H bend
C-H bend →
Vs
Vs
Spectra diff bet Alcohol and Ketone
OH
↓
C - H
↓
← C=O
← C-H bend
↑
C - H
← C-H bend
Spectra diff bet Alcohol and Ketone

15. ← C-H stretch
← C-H stretch
← C-H stretch
← C-H stretch
← C=O stretch C=O stretch →
O-H
↓
O-H
↓
← C-H bend
← C-H bend
C-H bend →
C-H bend →
C=C stretch →
Finger printing
region
Finger printing
region
Finger printing
region
Finger printing
region
Propanal (Aldehyde) Butan-2-one (Ketone)
Butanol (Alcohol) But-2-en-1-ol ( Alcohol + Alkene)
IR spectra organic compound with diff functional gps
C – H stretch CHO
(2720)
H
‫׀‬
CH3-CH2-C=O
O
‖
CH3CH2-C-CH3
CH3-CH=CH-CH2-OH
CH3-CH2-CH2-CH2OH

16. Operating Principle Double Beam Infrared Spectrometer
Double beam splitter
• Direct half radiation through sample and other half through reference
• Allow radiation passing through sample and compare it with reference
• Two beams recombined at detector.
• Signal from sample/reference are compared to determine if sample
absorb radiation emitted from source
Reference
• Solvent to dissolve sample
• Reference use to eliminate instrument fluctuation,
absorption due to impurities in solvent and all interferences.
• IR Absorption due to solute using the reference
Monochromator
• Allow radiation of particular wavelength to pass through
Fourier transformation
• Allow several wavelength through the sample at the same time and analyse the results
• Using mathematical techniques to determine the amplitude/intensity of each single frequency
• Fourier transformation- Intensity of IR radiation at each frequency determined separately
Recorder/Output
•Scanning wavenumber from 400 to 4000cm-1
• Spectrum of Abs/Trans vs frequency/wavenumber produced
Light Source
• Provide IR radiation

17. Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenses
http://creativecommons.org/licenses/
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorial
http://lawrencekok.blogspot.com