Sediment-associated reactions of aromatic amines. 2. QSAR development

Area of Science:

• Environmental Chemistry
• Soil Science
• Organic Geochemistry

Background:

• Aromatic amines are common in organic chemicals, but their environmental fate, particularly binding kinetics in soils and sediments, is not fully understood.
• Irreversible binding via nucleophilic addition and oxidative radical coupling dominates aromatic amine fate.
• Predicting reaction kinetics in natural systems requires understanding molecular properties influencing sorption.

Purpose of the Study:

• To investigate the sorption kinetics of substituted anilines in sediment slurries.
• To identify molecular descriptors that correlate with and predict the reaction rates of aromatic amines.
• To differentiate between factors controlling rapid and slow sorption processes.

Main Methods:

• Measured sorption kinetics of various anilines with ortho, meta, and para substituents in sediment slurries.
• Characterized sorption kinetics into rapid and slow phases.
• Correlated initial sorption rates with molecular descriptors like pKa, Hammett sigma constants, and redox potentials.

Main Results:

• Sorption kinetics exhibited an initial rapid phase followed by a slower phase.
• Initial sorption rates were influenced by the type and position of aniline substituents.
• Dissociation constants (pKa) and Hammett sigma constants showed the strongest linear correlations with initial reaction rates.

Conclusions:

• Dissociation constants and Hammett sigma constants are valuable for predicting substituted aniline reaction rates in sediments.
• The slow sorption phase is less sensitive to substituent effects, suggesting it's limited by binding site availability rather than electron transfer rates.