The C=O stretching frequency
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The C=O stretching frequency. aldehydes and ketones. A summary of the principle infrared bands and their assignments. R is an aliphatic group. Aliphatic Aldehyde. Figure IR-14. Butanal, neat liquid, thin film: CH 3 CH 2 CH 2 CHO. Aliphatic Ketone.

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The C=O stretching frequency

aldehydes and ketones


A summary of the principle infrared bands and their assignments. R is an aliphatic group.


Aliphatic Aldehyde assignments. R is an aliphatic group.

Figure IR-14. Butanal, neat liquid, thin film: CH3CH2CH2CHO


Aliphatic Ketone assignments. R is an aliphatic group.

Figure IR-35. 5-Hexene-2-one, neat liquid: CH2=CH2CH2CH2COCH3


The C=O stretching frequency assignments. R is an aliphatic group.

esters


A summary of the principle infrared bands and their assignments. R is an aliphatic group.


Aliphatic Ester assignments. R is an aliphatic group.

Figure IR-33. Methyl acetate in 0.1 mm NaCl cells: CH3CO2CH3


neat assignments. R is an aliphatic group.

CCl4


Aliphatic Ester assignments. R is an aliphatic group.

Figure IR-34. Vapor and liquid spectra of ethyl n-hexanoate: CH3CH2CH2CH2CH2CO2CH2CH3


The C=O stretching frequency assignments. R is an aliphatic group.

aliphatic acids


A summary of the principle infrared bands and their assignments. R is an aliphatic group.


Aliphatic Acid assignments. R is an aliphatic group.

Figure IR-26. The liquid,

vapor and CCl4 soln

spectra of hexanoic acid:

CH3(CH2)4 CO2H


The C=O stretching frequency assignments. R is an aliphatic group.

aliphatic amides


A summary of the principle infrared bands and their assignments. R is an aliphatic group.


KBr pellet assignments. R is an aliphatic group.

Amide I 

1662 cm-1

Amide II; 1634 cm-1


Secondary Amide assignments. R is an aliphatic group.

Figure IR-21. N-Methyl acetamide, neat liquid; thin film: CH3CONHCH3


Tertiary Amide assignments. R is an aliphatic group.

Figure IR-23. N,N-Dimethylacetamide, neat liquid; thin film: CH3CON(CH3)2


The C=O stretching frequency assignments. R is an aliphatic group.

anhydrides


A summary of the principle infrared bands and their assignments. R is an aliphatic group.


Anhydrides assignments. R is an aliphatic group.

Figure IR-36. Propionic anhydride, neat liquid: CH3CH2CO2COCH2CH3


The C=O stretching frequency assignments. R is an aliphatic group.

carboxylates


A summary of the principle infrared bands and their assignments. R is an aliphatic group.


C=O in an acid 1700 cm assignments. R is an aliphatic group.-1; C-O-C stretch 1300 to 1000 cm-1,

say in ethers  1150 cm-1. Averaging a C=O with a C-O-C results in: (1700 + 1150)/2 = 1425 cm-1. Naively, we would estimate a bond and a half would have a frequency of 1425 cm-1


1410 cm assignments. R is an aliphatic group.-1

1560 cm-1

(1560+ 1410)/2 = 1485 cm-1


The C=C bond stretch assignments. R is an aliphatic group.


A summary of the principle infrared bands and their assignments. R is an aliphatic group.


Figure IR-9 assignments. R is an aliphatic group.. 1-Heptene; neat sample, thin film:

H2C=CH-CH2CH2CH2CH2CH3


The C=C bond stretch when next to a heteroatom assignments. R is an aliphatic group.


A summary of the principle infrared bands and their assignments. R is an aliphatic group.


Figure IR-40 assignments. R is an aliphatic group.. 2,5-Dimethoxy2,5-dihydrofuran, neat liquid:


Figure IR-41 assignments. R is an aliphatic group.. 2,3-Dihydrofuran, neat liquid:


The cumulative C=C bond stretch assignments. R is an aliphatic group.


The NO assignments. R is an aliphatic group.2 stretching frequency


A summary of the principle infrared bands and their assignments. R is an aliphatic group.


Aromatic Rings assignments. R is an aliphatic group.

Ring breathing motions

1600-1585

1500-1400

Both often appear as doublets


Benzene, neat, thin film: assignments. R is an aliphatic group.


4-Chloro-2-nitrophenol, KBr pellet: assignments. R is an aliphatic group.


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