IB Chemistry on Nuclear Magnetic Resonance (NMR) Spectroscopy and Spin spin coupling
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Transcript of IB Chemistry on Nuclear Magnetic Resonance (NMR) Spectroscopy and Spin spin coupling
Electromagnetic Radiation and Spectroscopy
Radiowaves
Nuclear spin
Nuclear Magnetic Resonance Spectroscopy
• Organic structure determination • MRI and body scanning
Infra Red
Molecular vibration
Infra Red Spectroscopy
UV or visible
Transition of outer most valence electrons
• Organic structure determination • Functional gp determination • Measuring bond strength • Measuring degree unsaturation in fat • Measuring level of alcohol in breath
Electromagnetic Radiation
UV Spectroscopy Atomic Absorption Spectroscopy
• Quantification of metal ions • Detection of metal in various samples
Electromagnetic Radiation Interact with Matter (Atoms, Molecules) = Spectroscopy
Main features of HNMR Spectra 1. Number of different absorption peaks – Number of different proton/chemical environment
2. Area under the 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 the 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 away. (Higher frequency for resonance to occur)
- Measured in ppm (δ) 4. Splitting pattern - Due to spin-spin coupling - The number of peak split is equal to number of hydrogen on neighbouring carbon +1 (n+1) peak
Nuclear Magnetic Resonance Spectroscopy (NMR)
Splitting Pattern NMR spectrum of CH3CH2Br
http://chemwiki.ucdavis.edu/Physical_Chemistry/Quantum_Mechanics/Atomic_Theory/Electrons_in_Atoms/Electron_Spin
Singlet – Neighbouring Carbon with No H Doublet – Neighbouring Carbon with 1 H Triplet – Neighbouring Carbon with 2H Quartet – Neighbouring Carbon with 3H
• Equivalent H in same chemical environment have no splitting effect on each other • Equivalent H do not split each other • All Equivalent H in the same chemical environment will produce a same peak /signal. • Spin spin coupling – occurs when protons have different chemical shift • Splitting not observed for protons that are chemically equivalent/same chemical shift
Nuclear Magnetic Resonance Spectroscopy (NMR)
(n + 1 rule) • Equivalent H in same chemical environment do not split each other. • If a proton H has n equivalent protons on neighboring carbons, then the signal for H will be split into n + 1 peaks. • H nuclei split neighbouring H in CH3 into 2 peaks, called a doublet.
1H nuclei split the CH3 methyl gp into doublet • H can align with EMF or against EMF. • CH3 will experience 2 different EMF • One lower, one higher EMF • Split into doublet
EMF couple with magnetic field by H • Overall magnetic field experience CH3 lower • H from CH3 will absorb at lower radiofreq (upfield)
EMF
EMF couple with magnetic field by H • Overall magnetic field experience by CH3 higher • H from CH3 will absorb at higher radiofreq (downfield)
EMF
• CH3 spilt to doublet by 1 adj H • CH3 experience two slightly different magnetic field due to neighbouring H
MF MF
Split with relative intensity of 1 : 1
Downfield Upfield
Nuclear Magnetic Resonance Spectroscopy (NMR)
(n + 1 rule) • If a proton H has n equivalent protons on neighboring carbons, then the signal for H will be split into n + 1 peaks. • 2H nuclei split neighbouring H in CH3 into 3 peaks, called triplet.
2H nuclei split the CH3 methyl into triplet • H can align with EMF or against EMF. • CH3 will experience 3 different EMF • One lower, one higher , one no net change • Split into triplet (ratio 1 : 2 : 1 )
EMF couple with magnetic field by H • Both align against EMF (Net lower EMF) •Overall magnetic field experience CH3 lower • H from CH3, absorb at lower radiofreq (upfield)
EMF
EMF couple with magnetic field by H • Both H align with EMF (Net greater EMF) • Overall magnetic field experience by CH3 higher • H from CH3, absorb at higher radiofreq (downfield)
EMF
EMF MF MF
MF
MF
EMF couple with magnetic field by H • One align with and one against EMF • MF by H cancel each other • Overall magnetic field experience CH3 the same
Split with relative intensity of 1 : 2 : 1 • CH3 spilt to triplet by 2 adj H • CH3 experience three different magnetic field due to 2 adjacent H
Downfield Upfield
Nuclear Magnetic Resonance Spectroscopy (NMR)
(n + 1 rule) • If a proton H has n equivalent protons on neighboring carbons, then the signal for H will be split into n + 1 peaks. • 3 H nuclei split neighbouring H in CH2 into 4 peaks, called a quartet.
3H nuclei split the CH2 methylene into quartet • H can align with EMF or against EMF. • CH2 will experience 4 different EMF • Split into quartet (ratio 1 : 3 : 3 : 1 )
EMF couple with MF by H • Three H align against EMF (Net lower EMF) •Overall magnetic field experience CH2 lower • H from CH2, absorb at lower radiofreq (upfield)
EMF
EMF couple with MF by H • Three H align with EMF (Net greater EMF) • Overall magnetic field experience by CH2 higher • H from CH2, absorb at higher radiofreq (downfield)
EMF EMF
MF MF
EMF couple with MF by H • Two align with and one against EMF (higher) • Two align against and one with EMF (lower) • Two different MF experience by CH2 in 3 : 3 ratio
Split with relative intensity of 1 : 3 : 3 : 1 • CH2 spilt to quartet by 3 adjacent H • CH2 experience four different magnetic field due to 3 adjacent H
Upfield Downfield
Nuclear Magnetic Resonance Spectroscopy (NMR)
Singlet peak • H nuclei attach to electronegative atom , O - NO splitting – Singlet • H nuclei attach to neighbouring C without any H - NO splitting – Singlet • Equivalent H nuclei do not split each other but will split neighbouring H • CH3CH2OH, quartet, triplet and singlet split
• CH3 spilt to triplet by 2 adj H • CH3 experience three different magnetic field due to 2 adj H
• CH2 spilt to quartet by 3 adj H • CH2 experience four different magnetic field due to 3 adj H
• No signal splitting from coupling between hydroxyl proton and methylene proton of CH2 – despite 2 adjacent H • Protons attached to OH, undergo rapid chemical exchange, transfer rapidly from each other /loss of H • Spin coupling due to H (OH) on methylene proton CH2 is negligible /not seen. • NO triplet split on OH due to 2 adjacent H from CH2 – Only singlet
H H
| | HO- C- C- H
| | H H
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
Triplet split Quartet split
Singlet split
Equivalent Hydrogen in same chemical Environment (chemical Shift)
Equivalent H - Hydrogen attached to carbon in particular chemical environment • Equivalent H in same chemical environment have no splitting effect on each other • All Equivalent H will produce same signal/peak
O ║ CH3-C-O-CH2-CH3
HO-CH2-CH3
O ║ HO-C-CH2-CH3
O ║ CH3-C-CH2-CH2-CH3
Equivalent Hydrogen in same chemical Environment (chemical Shift)
4 different chemical environment • 4 absorption peak /chemical shift
3 equivalent H
2 equivalent H 2 equivalent H
3 equivalent H
2 equivalent H
3 equivalent H
1 equivalent H
3 different chemical environment • 3 absorption peak/chemical shift
3 equivalent H
3 equivalent H
2 equivalent H
3 different chemical environment • 3 absorption peak/chemical shift
1 equivalent H 2 equivalent H
3 equivalent H
3 different chemical environment • 3 absorption peak/chemical shift
12
3 2 1 3 2 3 2
3 2 1 3 2 3
Equivalent Hydrogen in molecule with plane of symmetry
Equivalent H - Hydrogen attach to carbon in particular chemical environment • Equivalent H in same chemical environment have no splitting effect on each other • Hydrogen atoms on neighbouring carbon can be equivalent if they are in the same environment • All Equivalent H in the same chemical environment/shift will produce a same peak /signal.
CH3
| CH3 – C -CH3
| CH3
1 chemical environment • 1 absorption peak/chemical shift
12 equivalent H O ║ CH3-CH2-C-CH2- CH3
2 different chemical environment • 2 absorption peak/chemical shift
4 equivalent H 6 equivalent H
CI | CH3-C-CH3
| H
2 different chemical environment • 2 absorption peak/chemical shift
1 equivalent H 6 equivalent H CH3
| HO-CH2- HC
| CH3
4 different chemical environment • 4 absorption peak/chemical shift
1 equivalent H
2 equivalent H 1 equivalent H
6 equivalent H
2
4 2
3 2 12
6 1 2 1 6 1
Equivalent H - Hydrogen attach to carbon in particular chemical environment • Equivalent H in same chemical environment have no splitting effect on each other • Hydrogen atoms on neighbouring carbon can be equivalent if they are in the same environment • All Equivalent H in the same chemical environment/shift will produce a same peak /signal.
O CH3
║ | H-C- C-CH3
| CH3
CH3
| H-C-OH
| CH3
3 different chemical environment • 3 absorption peaks /chemical shift
6 equivalent H 1 equivalent H
1 equivalent H
2 different chemical environment • 2 absorption peaks / chemical shift
1 equivalent H
9 equivalent H 1 equivalent H
O CH3
║ | CH3-C-O-C-H
| CH3
6 equivalent H
3 equivalent H
9 equivalent H
2 equivalent H
H CH3
| | CI- C- C- CH3
| | H CH3
2 different chemical environment • 2 absorption peaks / chemical shift
3 different chemical environment • 3 absorption peaks / chemical shift
9.7
Equivalent Hydrogen in molecule with plane of symmetry
9 1 6 1 1
9 2 6 3 1
CI CI | | C = C | | H H
CI CI CI
| | | H- C- C - C- H
| | | CI H CI
Equivalent H - Hydrogen attach to carbon in particular chemical environment • Equivalent H in same chemical environment have no splitting effect on each other • Hydrogen atoms on neighbouring carbon can be equivalent if they are in the same environment • All Equivalent H in the same chemical environment/shift will produce a same peak /signal.
2 equivalent H
1 equivalent H
2 equivalent H
4 equivalent H
H H | | CI- C- C- CI
| | H H
H H | | H - C- C- H
| | H H
2 different chemical environment • 2 absorption peak/ chemical shift
1 chemical environment • 1 absorption peak/chemical shift
1 chemical environment • 1 absorption peak/chemical shift
1 chemical environment • 1 absorption peak/chemical shift
6 equivalent H
4.5 6.1
Equivalent Hydrogen in molecule with plane of symmetry
2 2 1
6 4
Splitting Pattern by neighbouring H
O ║ CH3-C-O-CH2-CH3
HO-CH2-CH3
O ║ HO-C-CH2-CH3
O ║ CH3-C-CH2-CH2-CH3
4 chemical environment • 4 absorption peak
3 chemical environment • 3 absorption peak
3 chemical environment • 3 absorption peak
3 chemical environment • 3 absorption peak
12
• Equivalent H in same chemical environment have no splitting effect on each other • Equivalent H do not split each other • All Equivalent H in the same chemical environment will produce a same peak /signal.
Triplet
2 adj H
Septet 5 adj H
Singlet
No H
Triplet
2 adj H
Triplet
2 adj H
Quartet
3 adj H
Singlet OH – No split
Triplet
2 adj H
Singlet
No H
Quartet 3 adj H
Triplet
2 adj H
Quartet 3 adj H
Singlet No H
Splitting Pattern by neighbouring H
3 2 1 3 2 3 2
3 2 1 3 3 2
CH3
| CH3 – C -CH3
| CH3
1 chemical environment • 1 absorption peak
O ║ CH3-CH2-C-CH2- CH3
2 chemical environment • 2 absorption peak
CI | CH3-C-CH3
| H
2 chemical environment • 2 absorption peak
CH3
| HO-CH2- HC
| CH3
4 chemical environment • 4 absorption peak
2
4 2
Splitting Pattern by neighbouring H
• Equivalent H in same chemical environment have no splitting effect on each other • Equivalent H do not split each other • All Equivalent H in the same chemical environment will produce a same peak /signal.
Singlet No H
Triplet
2 adj H
Quartet 3 adj H
Doublet
1 adj H
Heptet 6 adj H
Doublet
1 adj H
Doublet
1 adj H
Singlet OH- No split
Nonet 8 adj H
3 2 12
6 1 1 2 6 1
O CH3
║ | H-C- C-CH3
| CH3
CH3
| H-C-OH
| CH3
3 chemical environment • 3 absorption peaks
2 chemical environment • 2 absorption peaks
O CH3
║ | CH3-C-O-C-H
| CH3
H CH3
| | CI- C- C- CH3
| | H CH3
2 chemical environment • 2 absorption peaks
3 chemical environment • 3 absorption peaks
9.7
• Equivalent H in same chemical environment have no splitting effect on each other • Equivalent H do not split each other • All Equivalent H in the same chemical environment will produce a same peak /signal.
Heptet 6 adj H
Singlet OH- No split
Doublet 1 adj H
Singlet No H
Doublet 1 adj H
Heptet 6 adj H
Singlet No H
Singlet No H
Singlet No H
Singlet No H
Splitting Pattern by neighbouring H
9 1 6 1 1
9 2 6 1 3
Singlet Splitting Pattern
• Equivalent H in same chemical environment have no splitting effect on each other • All Equivalent H in the same chemical environment will produce a same peak /signal. • Singlet can be due to presence of OH or no adjacent H
Singlet due to • Equivalent H in same chemical environment • No adj H
CH3
| CH3 – C -CH3
| CH3
Singlet No H
O CH3
║ | H-C- C-CH3
| CH3
Singlet No H
Singlet due to • Equivalent H in same chemical environment • No adj H
9.7
Singlet No H
H CH3
| | CI- C- C- CH3
| | H CH3
Singlet No H
Singlet No H
Singlet due to • Equivalent H in same chemical environment • No adj H
H H | | CI- C- C- CI
| | H H
Singlet due to • Equivalent H in same chemical environment • Equivalent H do not split each other
Singlet No H
9 2 4
12 9 1
Singlet Splitting Pattern
• Equivalent H in same chemical environment have no splitting effect on each other • All Equivalent H in the same chemical environment will produce a same peak /signal. • Singlet can be due to presence of OH or no adjacent H
Singlet No H
Singlet No H
Singlet due to • Equivalent H in same chemical environment • No adj H
Singlet No H
Singlet due to • Equivalent H in same chemical environment • Equivalent H do not split each other
H H | | H - C- C- H
| | H H
CH3
| CH3 – O-C -CH3
| CH3
O ║ HO-C-CH3
12
Singlet No H
Singlet due to • OH in COOH • No adj H
2
Singlet No H
O ║ HO-C-H
Singlet due to • OH in COOH • H in CHO
Singlet No H
10.6 8.3
Singlet No H
3 1 1 1
6 9 3
Spin Spin Coupling and Chemical Shift
NMR Spectrum
O ║ HO-C-CH2-CH3
3 diff proton enviroment, Ratio H - 3: 3 : 2 • Peak A – split to 3 – 2H on adj C • Peak B - No split – No H on adj C • Peak C – split to 4 – 3H on adj C
3 diff proton enviroment, ratio H - 3:2:1 • Peak A – split to 3 – 2H on adj C • Peak B – split to 4 – 3H on adj C • Peak C – No split – No H on adj C
A B
C
B
A
C
O ║ CH3-C-O-CH2-CH3
12
3 2 3
3 2 1
HO-CH2-CH3
NMR Spectrum
O ║ CH3-C-CH2-CH2-CH3
3 diff proton enviroment, Ratio H - 3:2:1 • Peak A – split to 3 – 2H on adj C • Peak B – split to 4 – 3H on adj C • Peak C – No split for OH
4 diff proton enviroment, Ratio H - 3:2:2:3 • Peak A – split to 3 – 2H on adj C • Peak B – split to 6 – 5H on adj C • Peak C – No split – No H on adj C • Peak D – split to 3 – 2H on adj C
A
B C
3
B
A C D
2 1
3 2 2 3
O
║
H-C-CH3
NMR Spectrum
O ║
CH3-C-O-CH2-CH2-CH3
4 diff proton enviroment, Ratio H – 3:2:2:3 • Peak A – split to 3 – 2H on adj C • Peak B – split to 6 – 5H on adj C • Peak C – No split – No H on adj C • Peak D – split to 3 – 2H on adj C
A
B C D
2 diff proton enviroment, Ratio H - 3:1 • Peak A – split to 2 – 1H on adj C • Peak B – split to 4 – 3H on adj C
9.8
A
B
3 2 2 3
3 1
NMR Spectrum
Molecule with plane of symmetry
3 diff proton enviroment, Ratio H - 6:1:1 • Peak A – split to 2 – 1H on adj C • Peak B – No split for OH • Peak C – split to 7 – 6H on adj C
CH3
| H-C-OH
| CH3
O CH3
║ |
CH3-C-O-C-H
|
CH3
A
B
C
A B
C
3 diff proton enviroment, Ratio H - 6:3:1 • Peak A – split to 2 – 1H on adj C • Peak B – No split – 0H on adj C • Peak C – split to 7 – 6H on adj C
Molecule with plane of symmetry
6 1 1
6 3 1
NMR Spectrum
Molecule with plane of symmetry
O
║
CH3-CH2-C-CH2-CH3
O CH3
║ |
H-C-C-CH3
|
CH3
2 diff proton enviroment, Ratio H – 6:4 • Peak A – split to 3 – 2H on adj C • Peak B – split to 4 – 3H on adj C
A
B
A
B
6 4
9 1
2 diff proton enviroment, Ratio H – 9:1 • Peak A – No split – No H on adj C • Peak B – No split – No H on adj C
Molecule with plane of symmetry
NMR Spectrum
Molecule with plane of symmetry
4 diff proton enviroment, Ratio H – 6:1:1:2 • Peak A – split to 2 – 1H on adj C • Peak B – split to 7 – 6H on adj C • Peak C – No split for OH • Peak D – split to 2 – 1H on adj C
CH3
|
HO-CH2-CH
|
CH3
A
B D C
2 diff proton enviroment, Ratio H – 6:1 • Peak A – split to 2 – 1H on adj C • Peak B – split to 7 – 6H on adj C
CH3-CH-CH3
| CI
A
B
Molecule with plane of symmetry
6 1 1 2
6 1
NMR Spectrum
2 diff proton enviroment, Ratio H – 3:5 • Peak A – No split – No H on adj C • Peak B – split to 3 – 2H on adj C • Peak C – split to 3 – 2H on adj C • Peak D – split to 2 – 1H on adj C
A B
Molecule with benzene ring
3
Molecule with benzene ring
5
2 1 2
C D
7.3 8
All H in benzene are consider • as 1 proton environment
All H in benzene are consider • as 1 proton environment
7.3 8
2
E
1
D
2 5
C
2
3 2
A
B
3 diff proton enviroment, Ratio H – 3 : 2 :5 • Peak A – split to 3 – 2H on adj C • Peak B – split to 4 – 3H on adj C • Peak C – split to 3 – 2H on adj C • Peak D – split to 3 – 2H on adj C • Peak E – split to 2 – 1H on adj C
NMR Spectrum
A C
Molecule with benzene ring
3
Molecule with benzene ring
5
2 1 2
D E
7.3 8
All H in benzene are consider • as 1 proton environment
All H in benzene are consider • as 1 proton environment
7.3 8
2
F
1
E
2 5
D
3
1 2
A
B
4 diff proton enviroment, Ratio H – 1 : 2 : 2 :5 • Peak A – No split for OH • Peak B – split to 3 – 2H on adj C • Peak C – split to 3 – 2H on adj C • Peak D – split to 3 – 2H on adj C • Peak E – split to 3 – 2H on adj C • Peak F – split to 2 – 1H on adj C
2
B
3 diff proton enviroment, Ratio H – 3 : 2 : 5 • Peak A – split to 3 – 2H on adj C • Peak B – split to 4 – 3H on adj C • Peak C – split to 3 – 2H on adj C • Peak D – split to 3 – 2H on adj C • Peak E – split to 2 – 1H on adj C
3
4
C
2
NMR Spectrum
A C
6
Molecule with benzene ring
5
2 1 2
D E
7.3 8
All H in benzene are consider • as 1 proton environment
1
B
3 diff proton enviroment, Ratio H – 6 : 1 : 5 • Peak A – split to 2 – 1H on adj C • Peak B – split to 7 – 6H on adj C • Peak C – split to 3 – 2H on adj C • Peak D – split to 3 – 2H on adj C • Peak E – split to 2 – 1H on adj C
5