N
X
C
Hal
O
N
S
P Si
Natural
Products
Solvents
C
C
C
C C
C
353
7.11 Carbonyl Compounds
353
Typical Ranges (v ~ in cm -1 )
Assignment
Range
Comments
COO–H st
3550–2500
Intensity variable
Subranges:
3550–3500
Free, sharp, only in highly diluted solutions
3300–2500
H-bonded, broad, often more than one band
In the same range: OH st, NH st, CH st, SiH st, SH st, PH st
C=O st
1800–1650
Strong; in Raman, weak to medium
1800–1740
Free (also in dicarboxylic acids)
1740–1650
H-bonded (dimer, also in dicarboxylic acids)
Subranges for H-bonded C=O:
1725–1700
al–COOH
1715–1690
C=C–COOH
1700–1680
ar–COOH
1740–1720
hal–C–COOH
1670–1650
Intramolecular H bond
OC–OH st, C–
OH δ
1440–1210
Of no practical significance
OC–OH δ oop 960–880
Medium, generally broad (only in dimers);
in the same range: =CH δ, ar CH δ, NH δ
(COO) – st as
1610–1550
Very strong; in α-halogen carboxylates near the
higher value, with more than one α-hal beyond
the normal range; in polypeptides at ≈1575
(COO) – st sy
1450–1400
Strong, of no practical significance, in
polypeptides at ≈1470
(COO) – δ
≈775
Formates, weak
≈925
Acetates
≈680
Benzoates
≈600
CF 3 COO –
Examples (v ~ in cm -1 )
H
O H
O
neat:
1727
in CCl 4 : 1756
1724
O H
O
neat:
1759
1718
in CCl 4 : 1768
1717
O H
O
in CCl 4 : 1704
solid: 1686