Rate constants of chlorine atom reactions with organic molecules in aqueous solutions, an overview.

Rate constants of chlorine atom (Cl(•)) reactions (k(Cl•)) 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 k(Cl•) values are generally in the 10(8)-10(9) mol(-1) dm(3) 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 k(Cl•) values are in the 1 × 10(9)-2 × 10(10) mol(-1) dm(3) s(-1) range. In the k(Cl•) = 1 × 10(10)-4 × 10(10) mol(-1) dm(3) 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 k(Cl•) measurements are recommended.