Table 3. Reaction energies and activation energies of the electron-transfer from substituted (1H)-3-hydroxy-4-oxoquinolines to dioxygen, at the B3LYP/BS2//B3LYP/BS1 level, computed using Marcus theory for electron transfer.
Unless otherwise noted, the 3-hydroxyl group remained in the deprotonated state. Substituents are shown ordered by increased values of their Hammet σm parameters (Hansch, Leo & Taft, 1991).
| In chlorobenzene | In water | |||
|---|---|---|---|---|
| Quinoline substituent | Activation energy (kcal mol−1) | Reaction energy (kcal mol−1) | Activation energy (kcal mol−1) | Reaction energy (kcal mol−1) |
| -NH2 | 3.4 | −1.5 | 2.0 | −4.8 |
| -COO− | 1.5 | −5.1 | 5.9 | 4.4 |
| -(CH2)4CH3 | 7.1 | 6.0 | 5.2 | 3.0 |
| -CH3 | 6.8 | 5.5 | 4.9 | 2.5 |
| -CH3 (protonated quinoline) | 86.2 | 58.1 | 46.9 | 38.7 |
| -F | 11.1 | 10.9 | 8.6 | 7.8 |
| -COCH3 | 22.5 | 21.5 | 16.6 | 16.5 |
| -CN | 24.6 | 22.9 | 18.3 | 18.0 |
| -NO | 23.9 | 23.7 | 20.0 | 20.0 |
| -NO2 | 41.2 | 33.1 | 31.1 | 27.5 |