Structure-reactivity studies on the nature of transients formed on reaction of ^•OH radicals with chloroiodoalkanes in aqueous solution

Abstract

The transient optical absorption bands (λ _max= 315 and 345 nm) formed on reaction of ^•OH radicals with 1-chloro-3-iodopropane in N₂O-saturated neutral aqueous solutions have been assigned to an OH-adduct formed between iodine atom and OH radicals (t_½= 1.5 µ s, Î μ ₃₅₀= 2.46 × 10³ dm³ mol^-1 cm^-1). In acidic solutions, iodine-centred radical cations (λ _max= 345 nm, t_½= 4.0 µ s, Î μ ₃₄₅= 2.41 × 10³ dm³ mol^-1 cm^-1) are formed at low solute concentrations and dimer radical cations (λ _max= 430 nm, t_½= 16.0 µ s, Î μ ₄₃₀= 6.7 × 10³ dm³ mol^-1 cm^-1) at high solute concentrations. In chloroiodomethane, the ^•OH radicals do not seem to form OH-adducts in neutral aqueous solutions. In acidic solutions, intramolecular radical cation (λ _max= 430 nm, t_½= 8.0 µ s, Î μ ₄₃₀= 2.63 × 10³ dm³ mol^-1 cm^-1) with oxidized iodine and chlorine is observed. The intermolecular dimer radical cations are formed at high solute concentration (λ _max= 500 nm).