N
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
348
7 IR
7.11 Carbonyl Compounds
7.11.1 Aldehydes
Typical Ranges (v ~ in cm -1 )
Assignment
Range
Comments
C–H comb
2900–2800
2780–2680
Weak, Fermi resonance with C–H δ at ≈1390
(for extreme position of C–H δ only one band)
Subranges:
2830–2810,
2720–2690
Aliphatic
2830–2810,
2750–2720
Aromatic, with o-substitution often higher
In the same range: cyclohexanes at ≈2700, weak
C=O st
1765–1645
Strong; in Raman, weak to medium
Subranges:
1740–1720
Aliphatic
1765–1730
α-Halogenated aliphatic
1710–1685
Aromatic
1695–1660
α,β-Unsaturated aromatic
1670–1645
Aromatic with intramolecular H bonds
C–H δ
1390
Weak, of no practical significance
C=O st
C–H comb
=C–H δ
%T
400
800
1200
1600
2000
2800
3600
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
348
7 IR
7.11 Carbonyl Compounds
7.11.1 Aldehydes
Typical Ranges (v ~ in cm -1 )
Assignment
Range
Comments
C–H comb
2900–2800
2780–2680
Weak, Fermi resonance with C–H δ at ≈1390
(for extreme position of C–H δ only one band)
Subranges:
2830–2810,
2720–2690
Aliphatic
2830–2810,
2750–2720
Aromatic, with o-substitution often higher
In the same range: cyclohexanes at ≈2700, weak
C=O st
1765–1645
Strong; in Raman, weak to medium
Subranges:
1740–1720
Aliphatic
1765–1730
α-Halogenated aliphatic
1710–1685
Aromatic
1695–1660
α,β-Unsaturated aromatic
1670–1645
Aromatic with intramolecular H bonds
C–H δ
1390
Weak, of no practical significance
C=O st
C–H comb
=C–H δ
%T
400
800
1200
1600
2000
2800
3600