N
X
C
Hal
O
N
S
P Si
Natural
Products
Solvents
C
C
C
C C
C
313
7.2 Alkenes
313
1652
1612
1830
1621
987
818
1800
1621
941
899
1607
(2270)
1636
CN
1645
1612
CHO
1618
(1704)
O
1618
(1684)
COO H
1635
1615
(1730)
(1706)
CO OCH 3
1637
(1735)
7.2.2 Allenes
Typical Ranges (v ~ in cm -1 )
Assignment
Range
Comments
(C=C)=C–H st
3050–2950
C=C=C st as
1950–1930 Strong, doublet in X–C=C=CH 2 if X other
than alkyl
Ring strain increases frequency:
C CH 2 ≈2020
C=C=C st sy
1075–1060 Weak, absent with symmetric substitution.
In Raman, strong
(C=C)=CH 2 δ oop ≈850
Strong; overtone at ≈1700 (weak)
X
C
Hal
O
N
S
P Si
Natural
Products
Solvents
C
C
C
C C
C
313
7.2 Alkenes
313
1652
1612
1830
1621
987
818
1800
1621
941
899
1607
(2270)
1636
CN
1645
1612
CHO
1618
(1704)
O
1618
(1684)
COO H
1635
1615
(1730)
(1706)
CO OCH 3
1637
(1735)
7.2.2 Allenes
Typical Ranges (v ~ in cm -1 )
Assignment
Range
Comments
(C=C)=C–H st
3050–2950
C=C=C st as
1950–1930 Strong, doublet in X–C=C=CH 2 if X other
than alkyl
Ring strain increases frequency:
C CH 2 ≈2020
C=C=C st sy
1075–1060 Weak, absent with symmetric substitution.
In Raman, strong
(C=C)=CH 2 δ oop ≈850
Strong; overtone at ≈1700 (weak)