Reaction of hydroxyl radicals with 1-bromo-N-iodoalkanes in aqueous solution: 2C-3E bonded radical cations

Abstract

The transient optical absorption bands (λ _max = 310, 350 nm) formed on reaction of OH radicals with 1-bromo-4-iodobutane (pH = 6) are assigned to OH-adduct. In acidic solutions (pH = 3.0), the OH adduct is converted to a transient band with λ _max = 440 nm. This band is assigned to intramolecular radical cation formed on p-orbital overlap of oxidized iodine with bromine. In case of 1-bromo-5-iodopentane, the transient optical absorption bands formed on the reaction of OH radicals at pH = 6.0 are at λ _max = 310 and 350 nm. In acidic aqueous solution (pH = 3.0), the OH adducts are converted to intramolecularly coordinated solute radical cation (λ _max = 410 nm) through acid catalysed dehydration reaction. In case of 1-bromo-3-iodopropane, the hydroxyl radicals react to form absorption band with λ _max = 400 nm and a small shoulder in 310-330 nm region at neutral pH. In acidic solutions (pH = 3.0), the absorption of 310-330 nm band decreases and that of 400 nm band increases. The transient band at 400 nm is assigned to intramolecular radical cation. A fraction of OH radical is able to react by electron transfer mechanism at neutral pH. The fraction of OH radical forming OH-adduct at neutral pH decreases and is converted to radical cation in acidic pH.