Competition kinetics using the UV/H2O2 process: a structure reactivity correlation for the rate constants of hydroxyl radicals toward nitroaromatic compounds.
The rate constants for hydroxyl radical reaction toward a set of nitroaromatic substrates kS, have been measured at 25 degrees C using competition experiments in the UV/H2O2 process. For a given pair of substrates S1 and S2, the relative reactivity beta (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 8.6 x 10(9) M(-1)s(-1). A quantitative structure-reactivity relationship was found using the Hammett equation. Assuming sigma values to be additive, a value of -0.60 was obtained for the reaction constant rho. This value agrees with the high reactivity and the electrophilic nature of HO* radical.
García Einschlag
Fernando S
FS
Instituto de Investigaciones Fisicoquímica Teóricas y Aplicadas, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Casilla de Correo 16, Sucursal 4, 1900 La Plata, Argentina. fgarciae@dalton.quimica.unlp.edu.ar
Carlos
Luciano
L
Capparelli
Alberto L
AL
D004785:Environmental Pollutants / Q000493:pharmacokinetics*; D006861:Hydrogen Peroxide / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry*; D009574:Nitro Compounds / Q000493:pharmacokinetics*; D010777:Photochemistry; D021281:Quantitative Structure-Activity Relationship; D014466:Ultraviolet Rays
D004785:Environmental Pollutants; D009574:Nitro Compounds; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide