The C=O stretching frequency aldehydes and ketones
A summary of the principle infrared bands and their assignments. R is an aliphatic group. C=O
C=C
aldehydes ketones esters carboxylic acids amides (Amide I) (Amide II) (Amide II) amide anhydrides carboxylates olefins
-NO2 nitro groups
R(C=O)H R(C=O)R R(CO2)R RCO2H RCONH2, RCONHR RCONH2 RCONHR RCONR2 R(CO2CO)R R(CO2)-, M+ R2C=CR2 R2C=CH2 R2C=C(OR)R RNO2
1740-1720 1730-1710 1750-1735 1720-1680 1670-1640 1650-1620 1550 1650-1620 1820, 1750 1600, 1400 1680-1640 1600-1675 1600-1630 1550, 1370
S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S, S(sh) S,S(sh) W(sh) M(sh) S(sh) S,S(sh)
14 35 33, 34 26,27,30 19, 21 19, 21 19, 21 23 36 42 10, 39, 40 9, 35 41 28
Aliphatic Aldehyde 100 90 % Transmittance
80 70 60 50
H-C=O Impurity peak, probably O-H
40 30
1730 cm-1
20 10 4000
3500
3000
2500
2000
Wavenumbers, cm
1500
1000
500
-1
Figure IR-14. Butanal, neat liquid, thin film: CH3CH2CH2CHO
Aliphatic Ketone 100
% Transmittance
80 60 40 20
1715 cm-1 0 4000
3500
3000
2500
2000
1500
1000
500
-1
Wavenumbers, cm
Figure IR-35. 5-Hexene-2-one, neat liquid: CH2=CH2CH2CH2COCH3
The C=O stretching frequency
esters
A summary of the principle infrared bands and their assignments. R is an aliphatic group. C=O
C=C
aldehydes ketones esters carboxylic acids amides (Amide I) (Amide II) (Amide II) amide anhydrides carboxylates olefins
-NO2 nitro groups
R(C=O)H R(C=O)R R(CO2)R RCO2H RCONH2, RCONHR RCONH2 RCONHR RCONR2 R(CO2CO)R R(CO2)-, M+ R2C=CR2 R2C=CH2 R2C=C(OR)R RNO2
1740-1720 1730-1710 1750-1735 1720-1680 1670-1640 1650-1620 1550 1650-1620 1820, 1750 1600, 1400 1680-1640 1600-1675 1600-1630 1550, 1370
S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S, S(sh) S,S(sh) W(sh) M(sh) S(sh) S,S(sh)
14 35 33, 34 26,27,30 19, 21 19, 21 19, 21 23 36 42 10, 39, 40 9, 35 41 28
Aliphatic Ester
100
% Transmittance
80 60 40 20
Top: CHCl3 vs CHCl3 Bottom: 2.5 % v/v un CHCl3
1720 cm-1
0 4000
3500
3000
2500
2000
1500
1000
500
Wavenumbers, cm-1
Figure IR-33. Methyl acetate in 0.1 mm NaCl cells: CH3CO2CH3
CCl4
neat 1746 cm-1
1748 cm-1
100
% Transmittance
80 60 40 20
Top: CHCl3 vs CHCl3 Bottom: 2.5 % v/v un CHCl3
1720 cm-1
0 4000
3500
3000
2500
2000 -1
Wavenumbers, cm
1500
1000
500
Aliphatic Ester The effect of phase on IR frequencies 120
% Transmittance
100 vapor: 106 °C
80 60 40
liquid film
20 0
4000
3500
3000
2500
2000
1500
1000
Wavenumber, cm-1
Figure IR-34. Vapor and liquid spectra of ethyl n-hexanoate: CH3CH2CH2CH2CH2CO2CH2CH3
The C=O stretching frequency aliphatic acids
A summary of the principle infrared bands and their assignments. R is an aliphatic group. C=O
C=C
aldehydes ketones esters carboxylic acids amides (Amide I) (Amide II) (Amide II) amide anhydrides carboxylates olefins
-NO2 nitro groups
R(C=O)H R(C=O)R R(CO2)R RCO2H RCONH2, RCONHR RCONH2 RCONHR RCONR2 R(CO2CO)R R(CO2)-, M+ R2C=CR2 R2C=CH2 R2C=C(OR)R RNO2
1740-1720 1730-1710 1750-1735 1720-1680 1670-1640 1650-1620 1550 1650-1620 1820, 1750 1600, 1400 1680-1640 1600-1675 1600-1630 1550, 1370
S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S, S(sh) S,S(sh) W(sh) M(sh) S(sh) S,S(sh)
14 35 33, 34 26,27,30 19, 21 19, 21 19, 21 23 36 42 10, 39, 40 9, 35 41 28
120
% Transmittance
100 vapor: 134 °C
80
Aliphatic Acid
60 40
liquid film
20 0
4000
3500
3000
2500
2000
1500
1000
W avenumber, cm -1
Figure IR-26. The liquid, vapor and CCl4 soln spectra of hexanoic acid:
1710 cm-1
CH3(CH2)4 CO2H
The C=O stretching frequency
aliphatic amides
A summary of the principle infrared bands and their assignments. R is an aliphatic group. C=O
C=C
aldehydes ketones esters carboxylic acids amides (Amide I) (Amide II) (Amide II) amide anhydrides carboxylates olefins
-NO2 nitro groups
R(C=O)H R(C=O)R R(CO2)R RCO2H RCONH2, RCONHR RCONH2 RCONHR RCONR2 R(CO2CO)R R(CO2)-, M+ R2C=CR2 R2C=CH2 R2C=C(OR)R RNO2
1740-1720 1730-1710 1750-1735 1720-1680 1670-1640 1650-1620 1550 1650-1620 1820, 1750 1600, 1400 1680-1640 1600-1675 1600-1630 1550, 1370
S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S, S(sh) S,S(sh) W(sh) M(sh) S(sh) S,S(sh)
14 35 33, 34 26,27,30 19, 21 19, 21 19, 21 23 36 42 10, 39, 40 9, 35 41 28
Amide I 1662 cm-1
KBr pellet Amide II; 1634 cm-1
Secondary Amide 100 90 % Transmittance
80 70 60 50 40 30 Amide I
20
Amide II
10 4000
3500
3000
2500
2000
1500
1000
500
Wavnumbers, cm-1
Figure IR-21. N-Methyl acetamide, neat liquid; thin film: CH3CONHCH3
Tertiary Amide 100
% Transmittance
80 60 40 20
No amide II band
0 4000
3500
3000
2500
2000
1500
1000
500
Wavenumbers, cm -1
Figure IR-23. N,N-Dimethylacetamide, neat liquid; thin film: CH3CON(CH3)2
The C=O stretching frequency
anhydrides
A summary of the principle infrared bands and their assignments. R is an aliphatic group. C=O
C=C
aldehydes ketones esters carboxylic acids amides (Amide I) (Amide II) (Amide II) amide anhydrides carboxylates olefins
-NO2 nitro groups
R(C=O)H R(C=O)R R(CO2)R RCO2H RCONH2, RCONHR RCONH2 RCONHR RCONR2 R(CO2CO)R R(CO2)-, M+ R2C=CR2 R2C=CH2 R2C=C(OR)R RNO2
1740-1720 1730-1710 1750-1735 1720-1680 1670-1640 1650-1620 1550 1650-1620 1820, 1750 1600, 1400 1680-1640 1600-1675 1600-1630 1550, 1370
S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S, S(sh) S,S(sh) W(sh) M(sh) S(sh) S,S(sh)
14 35 33, 34 26,27,30 19, 21 19, 21 19, 21 23 36 42 10, 39, 40 9, 35 41 28
Anhydrides 100
% Transmittance
80 60 40 20 0 4500
4000
3500
3000
2500
2000
1500
1000
500
Wavenumber, cm-1
Figure IR-36. Propionic anhydride, neat liquid: CH3CH2CO2COCH2CH3
The C=O stretching frequency
carboxylates
A summary of the principle infrared bands and their assignments. R is an aliphatic group. C=O
C=C
aldehydes ketones esters carboxylic acids amides (Amide I) (Amide II) (Amide II) amide anhydrides carboxylates olefins
-NO2 nitro groups
R(C=O)H R(C=O)R R(CO2)R RCO2H RCONH2, RCONHR RCONH2 RCONHR RCONR2 R(CO2CO)R R(CO2)-, M+ R2C=CR2 R2C=CH2 R2C=C(OR)R RNO2
1740-1720 1730-1710 1750-1735 1720-1680 1670-1640 1650-1620 1550 1650-1620 1820, 1750 1600, 1400 1680-1640 1600-1675 1600-1630 1550, 1370
S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S, S(sh) S,S(sh) W(sh) M(sh) S(sh) S,S(sh)
14 35 33, 34 26,27,30 19, 21 19, 21 19, 21 23 36 42 10, 39, 40 9, 35 41 28
1560 cm-1
1410 cm-1
The C=C bond stretch
A summary of the principle infrared bands and their assignments. R is an aliphatic group. C=O
C=C
aldehydes ketones esters carboxylic acids amides (Amide I) (Amide II) (Amide II) amide anhydrides carboxylates olefins
-NO2 nitro groups
R(C=O)H R(C=O)R R(CO2)R RCO2H RCONH2, RCONHR RCONH2 RCONHR RCONR2 R(CO2CO)R R(CO2)-, M+ R2C=CR2 R2C=CH2 R2C=C(OR)R RNO2
1740-1720 1730-1710 1750-1735 1720-1680 1670-1640 1650-1620 1550 1650-1620 1820, 1750 1600, 1400 1680-1640 1600-1675 1600-1630 1550, 1370
S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S, S(sh) S,S(sh) W(sh) M(sh) S(sh) S,S(sh)
14 35 33, 34 26,27,30 19, 21 19, 21 19, 21 23 36 42 10, 39, 40 9, 35 41 28
100
% Transmittance
80 60
HC=C stretches
C=C stretch
40 20
(CH2)4 rocking
CH3,CH2 symmetric and asymmetric stretches
CH3,CH2 bending vibrations out of plane H wag of vinyl group 900, 1000 cm-1)
0 4000
3500
3000
2500
2000
1500
1000
Wavenumbers, cm-1
Figure IR-9. 1-Heptene; neat sample, thin film: H2C=CH-CH2CH2CH2CH2CH3
500
The C=C bond stretch when next to a heteroatom
A summary of the principle infrared bands and their assignments. R is an aliphatic group. C=O
C=C
aldehydes ketones esters carboxylic acids amides (Amide I) (Amide II) (Amide II) amide anhydrides carboxylates olefins
-NO2 nitro groups
R(C=O)H R(C=O)R R(CO2)R RCO2H RCONH2, RCONHR RCONH2 RCONHR RCONR2 R(CO2CO)R R(CO2)-, M+ R2C=CR2 R2C=CH2 R2C=C(OR)R RNO2
1740-1720 1730-1710 1750-1735 1720-1680 1670-1640 1650-1620 1550 1650-1620 1820, 1750 1600, 1400 1680-1640 1600-1675 1600-1630 1550, 1370
S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S, S(sh) S,S(sh) W(sh) M(sh) S(sh) S,S(sh)
14 35 33, 34 26,27,30 19, 21 19, 21 19, 21 23 36 42 10, 39, 40 9, 35 41 28
100
% Transmittance
80 60 40 20 0 4000
3500
3000
2500
2000
1500
1000
Wavenumbers, cm -1 CH3O
O
500 OCH3
Figure IR-40. 2,5-Dimethoxy2,5-dihydrofuran, neat liquid:
100
% Transmittance
80 60 40 20
1610 cm-1
0 4000
3500
3000
2500
2000
1500
1000
500
Wavenumbers, cm-1 O
Figure IR-41. 2,3-Dihydrofuran, neat liquid:
1652 cm-1
The cumulative C=C bond stretch
1958 cm-1
The NO2 stretching frequency
A summary of the principle infrared bands and their assignments. R is an aliphatic group. C=O
C=C
aldehydes ketones esters carboxylic acids amides (Amide I) (Amide II) (Amide II) amide anhydrides carboxylates olefins
-NO2 nitro groups
R(C=O)H R(C=O)R R(CO2)R RCO2H RCONH2, RCONHR RCONH2 RCONHR RCONR2 R(CO2CO)R R(CO2)-, M+ R2C=CR2 R2C=CH2 R2C=C(OR)R RNO2
1740-1720 1730-1710 1750-1735 1720-1680 1670-1640 1650-1620 1550 1650-1620 1820, 1750 1600, 1400 1680-1640 1600-1675 1600-1630 1550, 1370
S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S(sh) S, S(sh) S,S(sh) W(sh) M(sh) S(sh) S,S(sh)
14 35 33, 34 26,27,30 19, 21 19, 21 19, 21 23 36 42 10, 39, 40 9, 35 41 28
1556
cm-1
1367 cm-1
+ ON O
O
+ N
O -
120
% Transmittance
100 80 60 40 20
symmetric and asymmetric -NO2 stretch 1510
0 4000
3500
3000
2500
2000
and 1320 cm-1
1500
Wavenumbers, cm-1
4-Chloro-2-nitrophenol, KBr pellet:
1000
500
Aromatic Rings Ring breathing motions 1600-1585 1500-1400 Both often appear as doublets
100
% Transmittance
80 60 carbon-carbon triple bond stretch
40 20 0 4000
3500
3000
2500
2000
1500
1000
500
Wavenumbers, cm-1
H
90
% Transmittance
80 70 60 overtones of the benzene ring
50 40 30 20 4000
3500
3000
2500
2000
Wavenumbers, cm-1
Benzene, neat, thin film:
1500
1000
500
