Illustrations from R T Morrison and R N Boyd Organic Chemistry NMR Chemical Shift Chemical Shift measure of local electron density ref ref 10 ID: 399064
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Slide1
Introduction to Spectroscopy
Illustrations from
R. T. Morrison and R. N. Boyd,
Organic ChemistrySlide2
NMR Chemical Shift
Chemical Shift ~ measure of local electron density
=
( - ref )/ref * 106 ppmSlide3
Peak Integrals
3.8 : 2.9 : 8.8 = 1.31 : 1 : 3.03 = 3.9 : 3 : 9
If formula is known C
11H16 : 16 H/15.5 units = 1.03 H per unitSlide4Slide5
Correlation ChartsSlide6Slide7
13
CSlide8
Spin-Spin Splitting
Multiplicity : singlet, doublet, triplet, quartet,
pentet
Determined by number of near neighborsN-Equivalent neighbors: multiplicity = N + 1Slide9Slide10
Branched Chains have Characteristic Patterns
Quartet-triplet = ethyl
Septet-doublet = gem-
dimethyl (geminal – attached to same atom)Slide11
Inequivalent
Neighbors
N-Neighbors: multiplicity = 2
NSlide12
Spin Systems
Mutually coupled (or isolated equivalent spins)
Two spin systemsSlide13
Unknown
Double bonds and rings:
C
cHhOoNnDbr = (2c-h+n+2)/2 (2*8-10+2)/2 = 4Slide14
Effect of Field Strength
Chemical Shift the same in
ppm
Multiplets have same spacing in Hz60 MHz: 10 ppm = 600 Hz 1 Hz = 0.0166 ppm500 MHz: 10 ppm = 5000 Hz 1 Hz = 0.002 ppmSlide15
500 MHz
Multiplets
simplified (more first order)
Better definition in aromatic regionMore sensitive (less sample or less time)Slide16
Infrared Spectroscopy
Molecular Vibrations
Characteristic of functional groups
Chain Branching%TSlide17Slide18
Aldehydes
and
KetonesSlide19
Aldehyde
RCHO 1725 cm
-1
Ketone R2CO 1710 cm-1 Cyclobutanones 1780 cm-1Aromatic ArCHO 1700 cm-1 Aromatic ArCOR 1690 cm-1
Cyclopentanones
1740 cm
-1
Conjugated
-C=C-CHO 1685 cm
-1
-C=C-C=O 1675 cm
-1
| | | Slide20
AlcoholsSlide21
Carboxylic AcidsSlide22
Aliphatic R-COOH 1700-1725 cm
-1
Conjugated -C=C-COOH 1680-1700 cm
-1Aromatic Ar-COOH 1680-1700 cm-1Slide23
Carboxylic Acid DerivativesSlide24
Esters R-COOR C=O 1714-1740 cm
-1
two bands C-O-R 1050-1300 cm-1 Slide25
EthersSlide26
PhenolsSlide27Slide28
-
CH2-CH2-CH2-CH2- rock
720 cm
-1