Spectral,kinetics, and redox properties of the transients formed on one‐electron oxidation of 4,4′‐thiodiphenol: A pulse radiolysis study

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. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 603–610, 1999