9.4 Aromatic Hydrocarbons
451
9.4.2 Polysubstituted Benzenes
Estimation of the position of the allowed π π * transition in multiply substituted
benzenes (λ max in nm, log ε ≈4)
Base value: 203.5
Substituent
Increment [nm]
–CH 3
3.0
–Cl
6.0
–Br
6.5
–OH
7.0
–O –
31.5
–OCH 3
13.5
–NH 2
26.5
–NHCOCH 3
38.5
–NO 2
65.0
–C– – – N
20.5
–CHO
46.0
–COCH 3
42.0
–COOH
25.5
451
9.4.2 Polysubstituted Benzenes
Estimation of the position of the allowed π π * transition in multiply substituted
benzenes (λ max in nm, log ε ≈4)
Base value: 203.5
Substituent
Increment [nm]
–CH 3
3.0
–Cl
6.0
–Br
6.5
–OH
7.0
–O –
31.5
–OCH 3
13.5
–NH 2
26.5
–NHCOCH 3
38.5
–NO 2
65.0
–C– – – N
20.5
–CHO
46.0
–COCH 3
42.0
–COOH
25.5