Covalent bonding of aromatic amine daughter products of 2,4-dinitroanisole (DNAN) with model quinone compounds representing humus via nucleophilic addition

Quinone Moieties Link the Microbial Respiration of Natural Organic Matter to the Chemical Reduction of Diverse Nitroaromatic Compounds

“…The partial abiotic disappearance of 4CNB in the presence of humic acids should be the subject of future research. Moreover, we once again attribute the nondetection of some of the nitroaromatics’ reduced daughter products, i.e., DAAN, 2,4-DAT, and 4-aminoanisole (4AAn), to the adduct formation reactions (such as the Michael addition) triggered by the humic acids’ quinone moieties. ,, …”

“…We also did not detect the final product from the complete reduction of 2,4-DNT, (2,4-diaminotoluene (2,4-DAT)). Based on our previous works, abiotic mechanisms lead to the disappearance of DAAN due to (i) coupling reactions with nitroso intermediates from DNAN and MENA reductions , and (ii) nucleophilic reactions with synthetic and naturally occurring quinones, forming Michael adducts and imines (Schiff bases). , The reactions between DAAN and quinones occur in seconds and irreversibly lock the aromatic amine into large NOM-like polymers . We have also shown that these reactions can occur under anaerobic conditions and without any catalyst. , Moreover, the aforementioned nucleophilic reactions between aromatic amines and quinone moieties of NOM are not restricted to DAAN and can occur in a variety of aromatic amines, − including 2,4-DAT, which explains the disappearance of these reduced products in our system.…”

“…52 We have also shown that these reactions can occur under anaerobic conditions and without any catalyst. 51,52 Moreover, the aforementioned nucleophilic reactions between aromatic amines and quinone moieties of NOM are not restricted to DAAN and can occur in a variety of aromatic amines, 53−56 including 2,4-DAT, 57 which explains the disappearance of these reduced products in our system. 3.5.…”

“…Based on our previous works, abiotic mechanisms lead to the disappearance of DAAN due to (i) coupling reactions with nitroso intermediates from DNAN and MENA reductions 49,50 and (ii) nucleophilic reactions with synthetic and naturally occurring quinones, forming Michael adducts and imines (Schiff bases). 51,52 The reactions between DAAN and quinones occur in seconds and irreversibly lock the aromatic amine into large NOM-like polymers. 52 We have also shown that these reactions can occur under anaerobic conditions and without any catalyst.…”

“…Moreover, we once again attribute the nondetection of some of the nitroaromatics' reduced daughter products, i.e., DAAN, 2,4-DAT, and 4-aminoanisole (4AAn), to the adduct formation reactions (such as the Michael addition) triggered by the humic acids' quinone moieties. 51,52,57 In a second batch of experiments, we used DNAN as a model nitroaromatic to show the relationship between the humic acid concentration and the rate of nitroaromatic reduction in the system (Figure 4). Despite a minor background DNAN reduction, a minimum humic acid concentration of 18 mg L −1 was required to transform the nitroaromatic effectively.…”