N
X
C
Hal
O
N
S
P Si
Natural
Products
Solvents
C
C
C
C C
C
317
7.5 Aromatic Hydrocarbons
317
7.5 Aromatic Hydrocarbons
Typical Ranges (v ~ in cm -1 )
Assignment
Range
Comments
ar C–H st
3080–3030
Often numerous bands; in the same range also
CH st of alkenes and small rings
ar C–C
1625–1575
Medium, often
doublet; generally
weak in benzene
derivatives having a
center of symmetry in
the ring
In the same range: C=C st, C=N st, C=O st, N=O st, C–C in
heterocyclics, NH δ
1525–1450
Medium, often doublet: Weak in:
O
O
In the same range: C=O st, N=O st, C–C in heterocyclics,
B–N st, CH 3 δ, CH 2 δ, NH δ
comb
2000–1650
Very weak; useful for determining substitution
patterns in 6-membered aromatic rings
In the same range: C=O st, B–H … B st, N + –H st, H 2 O δ
ar C–H δ ip 1250–950
Numerous bands of variable intensity; of no
practical significance. May be very strong in
Raman and, thereby, indicative of substitution
type
%T
400
800
1200
1600
2000
2800
3600
C–H st
C=C δ
C–H δ oop
skeletal
vibrations
overtones
and comb