Pulse radiolysis investigations on the nature of OH radical reactions with 1-fluoro-2-iodobenzene in aqueous solutions

Abstract

The transient optical absorption bands (λ_max = 310 nm, 330-350 nm, k = 3.2 ×10⁹ dm³ mol^-1 s^-1) formed on reaction of'OH radicals with 1-fluoro-2-iodobenzene in neutral aqueous solutions are assigned to OH-adduct, which decayed by second order kinetics with 2k = 2.9 ×10⁹ dm³ mol^-1 s^-1. The absorption band (λ_max = 630 nm) observed in acidic solutions (pH = 3) is assigned to solute radical cation formed on removal of an electron from iodine, which decayed by first order kinetics with k = 5.6×10⁵ s^-1. At pH = 1, the OH-adduct was found to react with H⁺ (k = 4.7 ×10⁵ s^-1) and formed a broad absorption band in 350 - 400 nm region. It is assigned to solute radical cation formed on removal of an electron from fluorine. Acid-catalyzed dehydration of OH-adduct is observed with ∼85% at iodine and ∼15% at fluorine. The iodine centered radical cation is a strong one-electron oxidant and is able to oxidize I^- and Br^- with rate constant in the diffusion controlled range. SO₄^- radical anion is able to undergo electron transfer with the solute and absorption bands due to iodine centered radical cation (λ = 630 nm), and OH-adduct (λ = 310, 330-370 nm) are observed.