A Laser Flash Photolysis Kinetic Study of Reactions of the Cl2 Radical Anion with Oxygenated Hydrocarbons in Aqueous Solution

A laser photolysis–long path laser absorption (LP-LPLA) experiment has been used to determine the rate constants for H-atom abstraction reactions of the dichloride radical anion (Cl2) in aqueous solution. From direct measurements of the decay of Cl2 in the presence of different reactants at pH 5 4 and I 5 0.1 M the following rate constants at T 5 298 K were derived: methanol, (5.1 6 0.3) · 104 M21 s21; ethanol, (1.2 6 0.2) · 105 M21 s21; 1-propanol, (1.01 6 0.07) · 105 M21 s21; 2-propanol, (1.9 6 0.3) · 105 M21 s21; tert.-butanol, (2.6 6 0.5) · 104 M21 s21; formaldehyde, (3.6 6 0.5) · 104 M21 s21; diethylether, (4.0 6 0.2) · 105 M21 s21; methyltert.-butylether, (7 6 1) · 104 M21 s21; tetrahydrofuran, (4.8 6 0.6) · 105 M21 s21; acetone, (1.41 6 0.09) · 103 M21 s21. For the reactions of Cl2 with formic acid and acetic acid rate constants of (8.0 6 1.4) · 104 M21 s21 (pH 5 0, I 5 1.1 M and T 5 298 K) and (1.5 6 0.8) z 103 M21 s21 (pH 5 0.42, I 5 0.48 M and T 5 298 K), respectively, were derived. A correlation between the rate constants at T 5 298 K for all oxygenated hydrocarbons and the bond dissociation energy (BDE) of the weakest C-H-bond of log k2nd 5 (32.9 6 8.9) 2 (0.073 6 0.022) · BDE/kJ mol21 is derived. From temperature-dependent measurements the following Arrhenius expressions were de-