N
X
C
Hal
O
N
S
P Si
Natural
Products
Solvents
C
C
C
C C
C
321
7.6 Heteroaromatics
321
Typical Ranges (v ~ in cm -1 )
Assignment
Range
Comments
N–H st
3450–3200
Medium, narrow; shifted by formation of
hydrogen bonds
Overtones
2100–1800
Weak, characteristic
Ring skeleton 1610–1360
Strong, sharp bands
C–H δ
1000–700
Strong, broad; difficult to identify
C–H st
3100–3000
Medium, sharp
CO–C st
1190–990
Medium or strong; of variable intensity
Pyridines
The frequencies of pyridines are very similar to those observed in benzenes. The
nitrogen atom behaves like a substituted carbon atom in benzenes.
5-Ring Heteroaromatics
O
N
H
S
NH st free
3500–3400
NH st H-bonded
3400–2800
CH st
≈3100
≈3100
≈3100
Ring skeleton: intensity variable,
generally multiplets
1610–1560
1510–1475
1590–1560
1540–1500
1535–1515
1455–1410
CH δ oop: generally strong
990–725
770–710
935–700