Rate constants of chlorine atom reactions with organic molecules in aqueous solutions, an overview
2022
Wojnárovits, László | Wang, Jianlong | Chu, Libing | Takács, Erzsébet
Rate constants of chlorine atom (Cl•) reactions (kCₗ•) determined using a large variation of experimental methods, including transient measurements, steady-state and computation techniques, were collected from the literature and were discussed together with the reaction mechanisms. The kCₗ• values are generally in the 10⁸–10⁹ mol⁻¹ dm³ s⁻¹ range when the basic reaction between the Cl• and the target molecule is H-atom abstraction. When Cl• addition to double bonds dominates the interaction, the kCₗ• values are in the 1 × 10⁹–2 × 10¹⁰ mol⁻¹ dm³ s⁻¹ range. In the kCₗ• = 1 × 10¹⁰–4 × 10¹⁰ mol⁻¹ dm³ s⁻¹ range, single-electron-transfer reactions may also contribute to the mechanism. The Cl• reactions with organic molecules in many respects are similar to those of •OH, albeit Cl• seems to be less selective as •OH. However, there is an important difference, as opposed to Cl• in the case of •OH single-electron-transfer reactions have minor importance. The uncertainty of Cl• rate constant determinations is much higher than those of •OH. Since Cl• reactions play very important role in the emerging UV/chlorine water purification technology, some standardization of the rate constant measuring techniques and more kCₗ• measurements are recommended.
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