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

• 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 = hf

hcE

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

Nuclear Magnetic Resonance Spectroscopy (NMR) • Involve nucleus (proton + neutron) NOT electron • Proton + neutrons = Nucleons • Nucleons like electrons have spin and magnetic moment (acts like tiny magnet)

Nuclei with even number of nucleon (12C and 16O) • Even number of proton and neutron – NO net spin • Nucleon spin cancel out each other –Nucleus have NO overall magnetic moment – NOT absorb radiowave

Nuclei with odd number of nucleon (1H, 13C, 19F, 31P) -Nucleon have net spin – Nucleus have NET magnetic moment – Absorb radiowave

• Nuclei with net spin – magnetic moment will interact with radiowaves • Nuclei have a “spin” associated with them (i.e., they act as if they were spinning about an axis) due to the spin associated with their protons and neutrons. • Nuclei are positively charged, their spin induces a magnetic field

• NMR spectroscopy does not work for nuclei with even number of protons and neutrons - nuclei have no net spin.

Nuclear Magnetic Resonance Spectroscopy (NMR)

Spin cancel each other

Net spin

Main features of HNMR Spectra 1. Number of diff absorption peaks – Number of diff proton/chemical environment 2. Area under peaks - Number of hydrogen in a particular proton/chemical environment (Integration trace) - Ratio of number of hydrogen in each environment 3. Chemical shift - Chemical environment where proton is in - Spinning electrons create own magnetic field, creating a shielding effect - Proton which are shielded appear upfield. (Lower frequency for resonance to occur) - Proton which are deshielded appear downfield. (Higher frequency for resonance to occur) - Measured in ppm (δ) 4. Splitting pattern - Due to spin-spin coupling - Number of peak split is equal to number of hydrogen on neighbouring carbon +1 (n+1) peak

Chemical Shift NMR spectrum CH3CH2Br

Number of peaks

Area under peaks Chemical shift

Splitting pattern

Nuclear Magnetic Resonance Spectroscopy (NMR)

Click here khan NMR videos.

Absence of External magnetic Field (EMF) • TWO nuclear spin have same energy level.

• External MF applied to atomic nuclei, MF of nuclei align themselves either with or against MF • Nuclei have a slight preference for parallel alignment with the applied field as it has a slightly lower energy • Nuclei can absorb energy to move/flip to higher energy level by absorbing energy in radio freq region

Presence of External Magnetic Field (EMF) • TWO nuclear spin split to TWO diff energy level

Presence of External Magnetic Field (EMF)

Absence of EMF • Two spins in same energy level

Presence of EMF • Two spins in diff energy level • Lower spin nuclei absorb radio freq equivalent to ∆E • Move to higher energy level

Lower spin nuclei align with magnetic field

High spin nuclei align against magnetic field

∆E

Nuclear Magnetic Resonance Spectroscopy (NMR)

H ׀ H – C – H

H ׀ H – C

Proton in nucleus – have spin – generate its magnetic field (MF) Electron around nucleus – have spin- also generate its MF Proton shielded by MF produced by electron - appear UPFIELD Proton deshielded by electron withdrawing gp - appear DOWNFIELD

Chemical Shift (Shielding Effect)

Presence of EMF • Two spins in diff energy level • Lower spin nuclei absorb radio freq equivalent to ∆E • Move to higher energy level

∆E

∆E is smaller

Without SHIELDING EFFECT • Energy of ∆E absorb by H to move to higher energy level

Upfield Downfield

SHIELDING EFFECT • Electron around H produce MF and shield the H • H in CH3 will experience less EMF (SHIELDED) • Absorb at lower radiofreq to move to higher level • ∆E absorb by H to move to higher energy level is less • Appear upfield.

Absence of EMF • Two spins in same energy level

Absence of EMF • Two spins in same energy level

Presence of EMF • Two spins at diff energy level

Presence of EMF • Two spins at diff energy level

MF

N

S

H nucleus proton

H nucleus shield by electron MF

proton MF

N

S

- H

H ׀ H – C – H

∆E

∆E is higher

DESHIELDING EFFECT • Electron withdrawn by C=O gp • Carbonyl gp has electron withdrawing effect • Less electron around H in CH3

• H in CH3 deshielded, experience greater EMF • ∆E absorb by H, to move to high energy is higher • Absorb at higher radiofreq, to move to high level • Appear downfield

Chemical Shift (Deshielding Effect)

Downfield Upfield

Presence of EMF • Two spins in diff energy level • Lower spin nuclei absorb radio freq equivalent to ∆E • Move to higher energy level

Absence of EMF • Two spins in same energy level

proton H nucleus

Presence of EMF • Two spins at diff energy level

Without SHIELDING EFFECT • Energy of ∆E absorb by H to move to higher energy level

S

N

MF

H nucleus deshield by elec MF

proton

Absence of EMF • Two spins in same energy level Presence of EMF

• Two spins at diff energy level

N

S

MF

Proton in nucleus – have spin – generate its magnetic field (MF) Electron around nucleus – have spin- also generate its MF Proton shielded by MF produced by electron - appear UPFIELD Proton deshielded by electron withdrawing gp - appear DOWNFIELD

H ׀ H – C – H

No shielding

∆E

∆E is smaller

Without any SHIELDING EFFECT • Energy of ∆E absorb by H to move to higher energy level

SHIELDING EFFECT • Electron around H produce MF and shield H • H in CH3 experience less EMF (SHIELDED) •∆E absorb by H to move to higher energy level is less • Appear upfield.

Chemical Shift (Shielding and Deshielding Effect)

∆E is higher

Absence of EMF • Two spins in same energy level

Presence of EMF • Two spins at diff energy level

Shielding Effect

H nucleus proton

MF

S

N

H nucleus deshield by elec MF

proton

DESHIELDING EFFECT • Electron withdrawn by C=O gp • Carbonyl gp has electron withdrawing effect • Less electron around H in CH3

• H in CH3 deshielded, experience greater EMF • ∆E absorb by H, to move to high energy is higher • Absorb at higher radiofreq, to move to high level • Appear downfield

H nucleus shield by elec MF

proton N

S

N

S

Deshielding Effect

MF

MF

Chemical Shift (Shielding and Deshielding Effect)

Shielding/Deshielding: • Electron circulate nucleus, create MF opposing external MF. • Each nucleus experience a slightly diff magnetic field • (Sum external field and field from electron cloud). • Energy a nucleus achieve resonance depend on its surrounding. • Freq absorption depend on electron density around nucleus

Chemical shift of various electron withdrawing gp

- Electron withdrawn from CH3 by C=O • Deshield H in CH3 • Absorb at slightly higher freq • Upfield ≈ 2.1

• Electron withdrawn from CH2 by COO • Stronger electron withdrawing effect • Higher ↑ Deshielding effect on H in CH2 • Absorb at Higher ↑ freq • Slightly Downfield ≈ 4.1

• Electron withdrawn by benzene • Stronger electron withdrawing effect • Higher ↑ deshielding effect on H • Absorb at Very high ↑ freq • Very Downfield ≈ 7.3 - 8

• Electron withdrawn from H by CHO • Very strong electron withdrawing effect • Higher ↑ Deshielding effect on H in CHO • Absorb at Very High ↑ freq • Very Very Downfield ≈ 9.7

• Electron withdrawn by COOH • Very strong electron withdrawing effect • Highest deshielding effect on H • Absorb at Very High ↑ freq • Very Very Very Downfield ≈ 12

Upfield

9.7

Downfield

12

Tetramethyl Silane (TMS) as STD •Strong peak upfield (shielded) •Silicon has lower EN value < carbon • Electron shift to carbon • H in CH3 more shielded • Experience lower EMF, absorb ↓ freq • UPFIELD ≈ 0

Click here for more complicated proton chemical shift

• 3 diff proton environment • Ratio of 3:2:1

CH3

• chemical shift ≈ 1 • integration = 3 H • split into 3

CH2

• chemical shift ≈ 3.8 • integration = 2 H • split into 4

OH

• chemical shift ≈ 4.8 • integration = 1 H • No split (Singlet)

3 2 1

Upfield

12

Advantages using TMS • Volatile and can be removed from sample • All 12 hydrogen in same proton environment • Single strong peak, upfield, wont interfere with other peak • All chemical shift, in ppm (δ) are relative to this STD, ( zero)

Nuclear Magnetic Resonance Spectroscopy (HNMR)

HO-CH2-CH3

CH3

׀ H3C – Si – CH3

׀ CH3

Click here Spectra database (Ohio State) Click here Spectra database (NIST)

TMS

Downfield

1H NMR Spectrum

O ‖

HO-C-CH2-CH3

3 diff proton environment, Ratio H - 3:2:3 • Peak A – split to 3 (2H on neighbour C) • Peak B - No split • Peak C – split to 4 (3H on neighbour C)

3 diff proton environment, Ratio H - 3:2:1 • Peak A – split to 3 (2H on neighbour C) • Peak B – split to 4 (3H on neighbour C) • Peak C – No split

A B

C

B

A

C

12

3 2 3

3 2 1

O ‖ CH3-C-O-CH2-CH3

O ‖ CH3-C-CH2-CH2-CH3

3 diff proton environment, Ratio H - 3:2:1 • Peak A – split to 3 (2H on neighbour C) • Peak B – split to 4 (3H on neighbour C) • Peak C – No split

4 diff proton environment, Ratio H - 3:2:2:3 • Peak A – split to 3 (2H on neighbour C) • Peak B – split to 6 (5H on neighbour C) • Peak C – No split • Peak D – split to 3 (2H on neighbour C)

A

B C

3

B

A C

D

2 1

3 2 2 3

HO-CH2-CH3

1H NMR Spectrum

O ‖ H-C-CH3

4 diff proton environment, Ratio H – 3:2:2:3 • Peak A – split to 3 (2H on neighbour C) • Peak B – split to 6 (5H on neighbour C) • Peak C – No split • Peak D – split to 3 (2H on neighbour C)

A B C D

2 diff proton environment, Ratio H - 3:1 • Peak A – split to 2 (1H on neighbour C) • Peak B – split to 4 (3H on neighbour C)

9.8

A

B

3 2 2 3

3 1

O ‖ CH3-C-O-CH2-CH2-CH3

1H NMR Spectrum

3 diff proton environment, Ratio H - 6:1:1 • Peak A – split to 2 (1H on neighbour C) • Peak B – No split • Peak C – split to 7 (6H on neighbour C)

O CH3

׀ ‖ CH3-C-O-C-H

׀ CH3

A

B

C

A

B

C

3 diff proton environment, Ratio H - 6:3:1 • Peak A – split to 2 (1H on neighbour C) • Peak B – No split • Peak C – split to 7 (6H on neighbour C)

Molecule with plane of symmetry

6 1 1

6 3 1

CH3

׀ H-C-OH

׀ CH3

Molecule with plane of symmetry

1H NMR Spectrum

2 diff proton environment, Ratio H – 6:4 • Peak A – split to 3 (2H on neighbour C) • Peak B – split to 4 (3H on neighbour C)

A

B

A

B

6 4

9 1

2 diff proton environment, Ratio H – 9:1 • Peak A – No split • Peak B – No split

Molecule with plane of symmetry

O ‖ CH3-CH2-C-CH2-CH3

Molecule with plane of symmetry

O CH3

׀ ‖ H-C-C-CH3

׀ CH3

1H NMR Spectrum

4 diff proton environment, Ratio H - 6:1:1:2 • Peak A – split to 2 (1H on neighbour C) • Peak B – split to 7 (6H on neighbour C) • Peak C – No split • Peak D – split to 2 (1H on neighbour C)

A

B D

C

2 diff proton environment, Ratio H – 6:1 • Peak A – split to 2 (1H on neighbour C) • Peak B – split to 7 (6H on neighbour C)

A

B

6 1 1 2

6 1

Molecule with plane of symmetry

CH3

׀ HO-CH2-CH

׀ CH3

Molecule with plane of symmetry CH3-CH-CH3

׀ CI

1H NMR Spectrum