Electron transfer reactions in aqueous solutions of 2,2'-thiodiethanol: a pulse radiolysis study

Abstract

The transient optical absorption band (λ _max=290 nm, ε = 2020 dm³mol^-1cm^-1) produced on pulse radiolysis of N₂O saturated aqueous solution (pH = 6.0-10.0) of 2,2'-thiodiethanol (TDE) has been assigned to the product of reaction of OH radicals with the solute. It decayed by second order kinetics with bimolecular rate constant of 1.7 × 10⁹ dm³ mol^-1 s^-1. The absolute rate constant for the reaction of OH radicals with the solute has been determined to be 1.4 × 10¹⁰ dm³ mol^-1 s^-1. The transient optical absorption band ( λ _max=505 nm, t_1/2=35 µ s, ε =6255 dm³ mol^-1 cm^-1) formed on pulse radiolysis of O₂ saturated aqueous solution of the solute (1.4 × 10^-2moldm^-3, pH = 1.5) has been assigned to dimer radical cation. Br^-₂ and Cl^-₂ are able to oxidize TDE with a bimolecular rate constant of 4.8 × 10⁸ and 1.1 × 10⁹ dm³ mol^-1 s^-1 respectively. The dimer radical cation of TDE oxidizes I^- with a bimolecular rate constant of 3.6 × 10⁹ dm³ mol^-1 s^-1.