http://lawrencekok.blogspot.com

Prepared by Lawrence Kok

Tutorial on Analytical Chemistry and Infrared Spectroscopy

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 SpectroscopyAtomic Absorption/Emission Spectroscopy

InfraRed /UV Spectroscopy

Mass Spectroscopy

High Performance Liquid Chromatography

Gas Liquid Chromatography

Paper/Thin Layer/Column Chromatography

Analytical Techniques

Quatitative analysisQualitative analysis Separation analysis

Flame testChemical test

Melting/boiling point Gravimetric Titration Distillation Precipitatio

n

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

• 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 108ms-1)• Radiation with high ↑ frequency – short ↓ wavelength• Electromagnetic radiation/photon carry a quantum of energy given by

E = hfhcE

h = plank constant = 6.626 x 10-34 Js f = frequency λ = wavelength

Click here notes spectroscopy

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

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 IRNo 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 momentOscillation of bonds - lead to oscillation of dipole - change in dipole

momentIR 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

+-

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

Click here khan organic videos.

Click here khan IR videos.

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

Tran

smitt

ance

/%A

bsor

banc

e

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.

Strength of bondSingle, 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

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

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)

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)

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)

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

CH3OHCH3CH2OH

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

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)

Propan -2-ol CH3CH(OH)CH3 Propanone CH3COCH3

Hexan-1-0l CH3(CH2)4CH2OH Hexan-2-0ne CH3CO(CH2)3CH3

C - H ↓

← C-H bendC-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

← 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-OHCH3-CH2-CH2-CH2OH

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

Acknowledgements

Thanks to source of pictures and video used in this presentation

Thanks to Creative Commons for excellent contribution on licenseshttp://creativecommons.org/licenses/

Prepared by Lawrence Kok

Check out more video tutorials from my site and hope you enjoy this tutorialhttp://lawrencekok.blogspot.com