Trichloroacetic acid dehalogenation by reductive radicals

Advanced oxidation processes, using either UVC/H₂O₂ or UVC/K₂S₂O₈, both in the presence of H₂CO₂ or CH₃OH are very efficient in mineralizing aqueous solutions of trichloroacetic acid (TCAA) leaving no toxic residues. The main reaction initiating TCAA depletion is its reduction by the radicals or CH₂OH to yield radicals and Cl⁻ anions. Further thermal reactions of lead to the formation of CO₂ and HCl. Molecular oxygen competes with TCAA for and CH₂OH radicals. However, in experiments under continuous irradiation of initially air-saturated solutions in closed reactors, the dissolved molecular oxygen concentration was depleted to low enough levels to favor the reaction of the reducing radicals with TCAA. A general reaction mechanism is proposed and discussed. The reaction between superoxide radical anions and TCAA was found to be of low efficiency.     

Formation of an observable intermediate during the reduction of [Co(NH3)5CN] by CRR(OH) radicals

CR¹R²OH, Rⁱ = CH₃ or H, react with the complex [Co^III(NH₃)₅CN]²⁺ to form an observable intermediate probably via bonding to the nitrogen of the cyanide. This intermediate isomerizes to form a second intermediate. The second intermediate decomposes into Co²⁺(aq), 5NH₄⁺, CN⁻ and R¹R²CO. The plausible structures of the intermediates are discussed. The radicals CH³, CH₂CHO, , and are considerably less reactive towards this complex, the formation of intermediates in their presence is not observed.