Table 5.
Thermochemistries (in kcal/mol) of the Forrester-Hepburn-mediated spin adduct formation at the PCM/B3LYP/6-31G**//B3LYP/6-31G* level of theory.
| free energies and enthalpies of reaction (kcal/mol)
| |||
|---|---|---|---|
| |||
| Anion (X) | Products (DMPO−-X) | ΔG298K,aq | ΔH298K,aq |
| SO32− | DMPO−-SO3− | 36.3 | −37.9 |
| SO32− | DMPO−-OSO2− | 36.0 | −41.4 |
| HSO3− | DMPO−-SO3H | 13.4 | −6.5 |
| HSO3− | DMPO−-OSO2H | 10.7 | −4.8 |
|
| |||
| |||
| DMPO−-X | Protonated nitrone (DMPOH-X) | ΔG298K,aq | ΔH298K,aq |
|
| |||
| DMPO−-SO3− | DMPOH-SO3− | −2.7 | −40.0 |
| DMPO−-OSO2− | DMPOH-OSO2− | −5.8 | −38.9 |
| DMPO−-SO3H | DMPOH-SO3H | 52.4 | 110.6 |
| DMPO−-OSO2H | DMPOH-OSO2H | 47.4 | 98.1 |
|
| |||
| |||
| DMPOH-X | Radical adduct (DMPO•-X) | ΔG298K,aq | ΔH298K,aq |
|
| |||
| DMPOH-SO3− | DMPO•-SO3− | −31.9 | −21.9 |
| DMPOH-OSO2− | DMPO•-OSO2− | −30.3 | −22.0 |
| DMPOH-SO3H | DMPO•-SO3H | −30.6 | −27.4 |
| DMPOH-OSO2H | DMPO•-OSO2H | −31.0 | −21.6 |
|
| |||
| Overall energetics for the Forrester-Hepburn Mechanism (sum of steps 1–3) | |||
|
| |||
| Radical adduct | ΔG298K,aq | ΔH298K,aq | |
|
| |||
| DMPO•-SO3− | 1.6 | −99.8 | |
| DMPO•-OSO2− | −0.1 | −102.4 | |
| DMPO•-SO3H | 35.2 | 76.6 | |
| DMPO•-OSO2H | 27.1 | 71.6 | |