Competition kinetics using the UV/H2O2 process: A structure reactivity correlation for the rate constants of hydroxyl radicals toward nitroaromatic compounds

FERNANDO S. GARCÍA EINSCHLAG; LUCIANO CARLOS; ALBERTO L. CAPPARELLI

CHEMOSPHERE

Año: 2003 p. 1 - 7

0045-6535

The rate constants for hydroxyl radical reaction toward a set of nitroaromatic substrates kS, have been measured at 25 ºC using competition experiments in the UV/H2O2 process. For a given pair of substrates S1 and S2, the relative reactivity b (defined as kS1=kS2) was calculated from the slope of the corresponding double logarithmic plot, i.e., of ln[S1] vs. ln[S2]. This method is more accurate and remained linear for larger conversions in comparison with the plots of ln[S1] and ln[S2] against time. The rate constants measured ranged from 0.33 to 8.6X109 M-1 s-1. A quantitative structure–reactivity relationship was found using the Hammett equation. Assuming s values to be additive, a value of 0.60 was obtained for the reaction constant r. This value agrees with the high reactivity and the electrophilic nature of HO radical.