N
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
314
7 IR
7.3 Alkynes
Typical Ranges (v ~ in cm -1 )
Assignment
Range
Comments
– – – – – C–H st
3340–3250
Strong, sharp; in the same region also OH st,
NH st
C– – – – – C st
2260–2100
Weak, sharp. In Raman, strong
Beyond normal range:
R–C– – – C–H; at the lower end of the cited range
R–C– – – C–R; usually 2 bands (Fermi resonance),
often missing if symmetrical, strong in Raman
Subranges:
≈2120
C–C– – – C–H
≈2220
C–C– – – C–C
≈2240
C–C– – – C–CN
≈2240
C–C– – – C–COOH
≈2240,
≈2140
C–C– – – C–COOCH 3
In the same range: C– – – Z st, X=Y=Z st, Si–H st
– – – – – C–H δ
700–600
Strong, broad; overtone at 1370–1220 (broad,
weak)
C–H st
C C st
%T
400
800
1200
1600
2000
2800
3600
C–H δ
overtone
C–H δ