9.3 Conjugated Alkenes
449
Increments
for each additional conjugated double bond
+30
for each exocyclic double bond
C C
+5
for each homoannular diene system
+39
For each substituent on
Increment
double bond system
α
β 
γ
δ and beyond
C-substituent
10
12
18
18
Cl
15
12
Br
25
30
OH
35
30
50
O–alkyl
35
30
17
31
O–COCH 3
6
6
6
6
S–alkyl
85
N(alkyl) 2
95
Solvent corrections
Solvent
Correction term
water
-8
hexane
11
cyclohexane
11
chloroform
1
methanol
0
ethanol
0
diethyl ether
7
dioxane
5
Example: Estimation of the absorption maximum in ethanol for
O
base value
215
2 additional conjugated double bonds
60
exocyclic double bond
5
homoannular diene system
39
1 β-C-substituent
12
3 additional C-substituents
54
solvent correction
0
estimated
385
experimental
388