Table 1.
| Free radical | Symbol | Half-life |
|---|---|---|
| Reactive oxygen species-ROS | ||
| Radicals | ||
| Superoxide | O2 •− | 10−6 s |
| Hydroxyl | OH• | 10−10 s |
| Alkoxyl radical | RO• | 10−6 |
| Peroxyl Radical | ROO• | 17 s |
| Non radicals | ||
| Hydrogen peroxide | H2O2 | Stable |
| Singlet oxygen | 1O2 | 10−6 s |
| Ozone | O3 | s |
| Organic peroxide | ROOH | Stable |
| Hypochlorous acid | HOCl | Stable (min) |
| Hypobromous acid | HOBr | Stable (min) |
| Reactive nitrogen species-RNS | ||
| Radicals | ||
| Nitric oxide | NO• | sa |
| Nitrogen dioxide | NO•2 | s |
| Non radicals | ||
| Peroxynitrite | ONOO− | 10−3 s |
| Nitrosyl cation | NO+ | s |
| Nitroxyl anion | NO− | s |
| Dinitrogen trioxide | N2O3 | s |
| Dinitrogen tetraoxide | N2O4 | s |
| Nitrous acid | HNO2 | s |
| Peroxynitrous acid | ONOOH | Fairly stable |
| Nitryl chloride | NO2Cl | s |
a The half life of some radicals depends on the environmental medium, for example the half life of NO• in an air saturated solution may be few minutes. S seconds, min minutes