Rate constants for the reactions of chloride monoxide radical (ClO center dot) and organic molecules of environmental interest

ClO center dot plays a key role in the UV/chlorine process besides Cl center dot, Cl2 center dot -, and center dot OH. In many experiments, ClO center dot proved to be the main reactant that destroyed the organic pollutants in this advanced oxidation process. About 200 rate constants of ClO center dot reactions were collected from the literature, grouped together according to the chemical structure, and the molecular structure dependencies were evaluated. In most experiments, ClO center dot was produced by the photolytic reaction of HClO/ClO-. For a few compounds, the rate constants were determined by the absolute method, pulse radiolysis. Most values were obtained in steady-state experiments by competitive technique or by complex kinetic calculations after measuring the pollutant degradation in the UV/chlorine process. About 30% of the listed rate constant values were derived in quantum chemical or in structure-reactivity (QSAR) calculations. The values show at least six orders of magnitude variations in the molecular structure. Molecules having electron-rich parts, e.g., phenol/phenolate, amine, or sulfite group have high rate constants in the range of 10(8)-10(9) mol(-1) dm(3) s(-1). ClO center dot is inactive in reactions with saturated molecules, alcohols, or simple aromatic molecules. The values determined in different laboratories, eventually by different techniques, may differ by more than one order of magnitude.