Photochemical Reactions of Uranyl Ions with Organic Compounds. IV. The Uranyl Fluorescence Quenching by Aliphatic Alcohols

Abstract

The relative rates for uranyl fluorescence quenching by aliphatic alcohols (methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and s-butyl alcohols) were measured under various conditions. The rates were increased in proportion to the perchloric acid concentration at pH <1, whereas the rates were smaller and nearly constant at the pH’s between 1–4; thus showing the involvement of both acid-dependent and acid-independent processes. Though the rates for both processes changed with the change in the alcohol structure (the polar substituent effect), the ratio of the two rate constants was nearly constant. The inhibitory effects of cupric ions (as a scavenger for the one-equivalent redox intermediates) suggested that the acid-dependent quenching process involves a two-equivalent redox or two consecutive one-equivalent redox steps between the same partners. The mechanisms of these quenching processes are discussed.