RATE CONSTANTS FOR REACTIONS OF IODINE ATOMS IN SOLUTION

Laser flash photolysis (at 248 or 308 nm) or aryl iodides in water or water/methanol solutions produces iodine atoms and phenyl radicals. Io dine atoms react rapidly with added I- to form I2- but do not react ra pidly with O2 (k less-than-or-equal-to 10(7) L mol-1 s-1). Iodine atom s oxidize phenols to phenoxyl radicals, with rate constants that vary from 1.6 x 10(7) L mol-1 s-1 for phenol to about 6 x 10(9) L mol-1 s-1 for 4-methoxyphenol and hydroquinone. Ascorbate and a Vitamin E analo gue are also oxidized very rapidly. N-Methylindole is oxidized by I at oms to its radical cation with a diffusion-controlled rate constant, 1 .9 x 10(10) L mol-1 s-1. Iodine atoms also oxidize sulfite and ferrocy anide ions rapidly but do not add to double bonds. The phenyl radicals , produced along with the I atoms, react with O2 to give phenylperoxyl radicals, which react with phenols much more slowly than I atoms. (C) 1995 John Wiley & Sons, Inc.