Spectral, kinetics, and redox properties of the transients formed on one-electron oxidation of 4,4'-thiodiphenol: a pulse radiolysis study

Abstract

The transient absorption bands ( λ _max = 330, 525 nm, k_f = 5 × 10⁹ dm³ mol^-1 s^-1) obtained on pulse radiolysis of N₂O-saturated neutral aqueous solution of 4,4'-thiodiphenol (TDPH) are due to the reaction of TDPH with ^•OH radicals and are assigned to phenoxyl radical formed on fast deprotonation of the solute radical cation. The reaction of specific one-electron oxidants (Cl₂^•-, Br₂^•-, N₃^•, TI²⁺, CCl₃OO^•) with TDPH also produced similar transient absorption bands. The phenoxyl radicals are also produced on pulse radiolysis of N₂-saturated solution of TDPH in 1,2-dichloroethane. The nature of transient absorption spectrum obtained on reaction of ^•OH radicals with TDPH is not affected in acidic solutions, showing that OH-adduct is not formed in neutral solutions. The oxidation potential for the formation of phenoxyl radical is determined to be 0.98 V.