CATALYSIS OF THE REDUCTION OF TL+ AND OF CH2CL2 BY COLLOIDAL SILVER IN AQUEOUS-SOLUTION

(CH3)2COH radicals (1-hydroxy-1-methylethyl) do not reduce Tl+ or CH2Cl2 in homogeneous aqueous solution. In the presence of 2.5 × 10-4 g atom/L of colloidal silver, Tl+ is reduced to yield colloidal thallium, and CH2Cl2 to yield Cl- plus CH3Cl. These reactions occur in competition with the silver-catalyzed reduction of water. Tl+ is reduced in a one-electron transfer reaction and CH2Cl2 in a two-electron transfer process. The effects are understood in terms of the colloidal particles acting as a pool for electrons that is continuously charged by the organic radicals and discharged by water or dissolved substrates. The specific rate for the CH2Cl2 reduction at the silver pool is 4.3 × 103 times greater than that of the water reduction. Electrochemical considerations are carried out to estimate a stationary potential of -0.62 V (vs. the standard hydrogen electrode) for the electron pool and to discuss the energetics of the observed reactions and the possible role of adsorbed hydrogen atoms. Colloidal silver and organic radicals were radiolytically produced. © 1979 American Chemical Society.