Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 30, 2001
Publication Date: June 30, 2001
Citation: Anthony C. Pierpoint, Cathleen J. Hapeman, and Alba Torrents
A linear free energy study of ring-substituted aniline ozonation for developing treatment of aniline-based pesticide wastes
Submitted to Journal of Agricultural and Food Chemistry
Accepted by Journal: 5/30/01
Interpretive Summary: Scientists use models to predict the effectiveness of chemical waste mitigation strategies under different conditions. These models use chemical constants that are derived from empirical observations and/or theoretical calculations. Anilines, organic compounds containing nitrogen, are present in a variety of waste streams including textiles, pharmaceuticals, and pesticides. This study uses reaction mechanisms and chemical properties to develop constants that describe the reactivity of anilines to a waste treatment technology that involves ozonation and subsequent biodegradation. The results showed that previous constants were inadequate. New relationships were examined that were more accurate. In future studies, these new constants will be evaluated for their predictiveness in remediating soils contaminated with aniline-based compounds.
Linear free energy relationships have long been used in physical organic chemistry to elucidate reaction mechanisms and estimate reactivities of compounds using known physical and chemical properties. Anilines are present in a variety of industrial waste streams including textiles, pharmaceuticals, and pesticides. The relative rate constants for the reaction of ozone were determined for several substituted anilines in aqueous solutions at pH 6.5 and 1.5. At pH 6.5, with the exception of m- and p-nitroaniline, the rate constants obey Hammett's equation; log(k(x)/k(H))=sigma*rho. The departure of m- and p-nitroaniline may be explained by direct conjugation of the reaction center. The commonly used sigma(para)minus value of 1.27, which extends the range of applicability of the Hammett equation, was insufficient to account for the conjugation effects on ozonation of p-nitroaniline; rho=-1.48 (R=0.973). Use of amine group atomic charge determinations significantly improved correlations;(k(x)/k(H))= 48.7*delta-18.2 (R=0.996). A linear plot of Hammett constants versus relative rate data at pH 1.5 showed poor correlation; rho = 0.72 (R = 0.572). Poor correlation was similarly observed for amine group atomic charge determinations, suggesting that other reaction mechanisms are involved.