Proton dissociation constants (pKa) of the compounds (cL = 10 or 50 μM) determined by UV-visible spectrophotometric titrations. {T = 25 °C; I = 0.1 M (KCl); 30% (v/v) DMSO/H2O}.
| Compound | R | pKa (NH+amino) | pKa (OHphenolic) | c L | |
|---|---|---|---|---|---|
| 2AP |
|
—a | 4.41 ± 0.02 | 10.36 ± 0.02 | 50 μM |
| 4 |
|
H | 4.82 ± 0.01 | 10.63 ± 0.02 | 50 μM |
| 8a | CH2-Ph | 4.58 ± 0.03 | 10.44 ± 0.04 | 50 μM | |
| 8b | CH2-(p-F)C6H4 | 4.23 ± 0.04 | 10.36 ± 0.02 | 10 μM | |
| 8c | CH2-(p-Cl)C6H4 | 4.34 ± 0.05 | ∼10.8 | 10 μM | |
| 8d | CH2-(p-Br)C6H4 | 3.94 ± 0.02 | ∼11.1 | 10 μM | |
| 8e | CH2-(p-CN)C6H4 | 3.85 ± 0.01 | ∼11.0 | 10 μM | |
| 8g | CH2-(p-CH3)C6H4 | 4.75 ± 0.03 | 10.34 ± 0.05 | 50 μM | |
| 8h | CH2-(p-MeO)C6H4 | 4.76 ± 0.03 | ∼10.6 | 50 μM | |
a
Reference compound.