Abstract
Nitroaromatic compounds are widely used in agricultural pesticides, pharmaceuticals, military explosives, and other applications. They enter the environment via manufacturing and municipal wastewater discharges and releases from agricultural and military operations. Because of their ubiquity and toxicity, they are considered an important class of environmental contaminants. Nitroaromatics are known to undergo reductive transformation to aromatic amines, and under aerobic conditions they are susceptible to coupling reactions which may lead to their irreversible incorporation into soil organic matter. However, there is also evidence of coupling reactions in the absence of oxygen between reduced intermediates of the insensitive munitions compound 2,4-dinitroanisole, leading to the formation of azo dimers. The formation of such products is a concern since they may be more toxic than the original nitroaromatic compounds. The objective of this research is to provide evidence of the anaerobic formation of azo coupling products. 4-Nitroanisole was used as a model compound and was spiked into incubations containing anaerobic granular sludge with H2 as the electron donor. Using liquid chromatography, UV–Vis spectroscopy, and mass spectrometry, the formation of the azo dimer 4,4′-dimethoxyazobenzene was confirmed. However, due to the instability of the azo bond under the reducing conditions of our incubations, the azo dimer did not accumulate. Consequently, 4-aminoanisole was the major product formed in our experiment. Other minor suspected coupling products were also detected in our incubations. The results provide clear evidence for the temporal formation of at least one azo dimer in the anaerobic reduction of a model nitroaromatic compound.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 372-380 |
| Number of pages | 9 |
| Journal | Chemosphere |
| Volume | 195 |
| DOIs | |
| State | Published - Mar 1 2018 |
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Keywords
- 2,4-Dinitroanisole (DNAN)
- Anaerobic biotransformation
- Azobenzenes
- Insensitive munitions compounds
- Nitroaromatics
ASJC Scopus subject areas
- Environmental Chemistry
- Chemistry(all)
Cite this
Evidence of anaerobic coupling reactions between reduced intermediates of 4-nitroanisole. / Kadoya, Warren M.; Sierra Alvarez, Maria Reye; Wong, Stanley; Abrell, Leif M; Mash, Eugene A; Field, James A.
In: Chemosphere, Vol. 195, 01.03.2018, p. 372-380.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Evidence of anaerobic coupling reactions between reduced intermediates of 4-nitroanisole
AU - Kadoya, Warren M.
AU - Sierra Alvarez, Maria Reye
AU - Wong, Stanley
AU - Abrell, Leif M
AU - Mash, Eugene A
AU - Field, James A
PY - 2018/3/1
Y1 - 2018/3/1
N2 - Nitroaromatic compounds are widely used in agricultural pesticides, pharmaceuticals, military explosives, and other applications. They enter the environment via manufacturing and municipal wastewater discharges and releases from agricultural and military operations. Because of their ubiquity and toxicity, they are considered an important class of environmental contaminants. Nitroaromatics are known to undergo reductive transformation to aromatic amines, and under aerobic conditions they are susceptible to coupling reactions which may lead to their irreversible incorporation into soil organic matter. However, there is also evidence of coupling reactions in the absence of oxygen between reduced intermediates of the insensitive munitions compound 2,4-dinitroanisole, leading to the formation of azo dimers. The formation of such products is a concern since they may be more toxic than the original nitroaromatic compounds. The objective of this research is to provide evidence of the anaerobic formation of azo coupling products. 4-Nitroanisole was used as a model compound and was spiked into incubations containing anaerobic granular sludge with H2 as the electron donor. Using liquid chromatography, UV–Vis spectroscopy, and mass spectrometry, the formation of the azo dimer 4,4′-dimethoxyazobenzene was confirmed. However, due to the instability of the azo bond under the reducing conditions of our incubations, the azo dimer did not accumulate. Consequently, 4-aminoanisole was the major product formed in our experiment. Other minor suspected coupling products were also detected in our incubations. The results provide clear evidence for the temporal formation of at least one azo dimer in the anaerobic reduction of a model nitroaromatic compound.
AB - Nitroaromatic compounds are widely used in agricultural pesticides, pharmaceuticals, military explosives, and other applications. They enter the environment via manufacturing and municipal wastewater discharges and releases from agricultural and military operations. Because of their ubiquity and toxicity, they are considered an important class of environmental contaminants. Nitroaromatics are known to undergo reductive transformation to aromatic amines, and under aerobic conditions they are susceptible to coupling reactions which may lead to their irreversible incorporation into soil organic matter. However, there is also evidence of coupling reactions in the absence of oxygen between reduced intermediates of the insensitive munitions compound 2,4-dinitroanisole, leading to the formation of azo dimers. The formation of such products is a concern since they may be more toxic than the original nitroaromatic compounds. The objective of this research is to provide evidence of the anaerobic formation of azo coupling products. 4-Nitroanisole was used as a model compound and was spiked into incubations containing anaerobic granular sludge with H2 as the electron donor. Using liquid chromatography, UV–Vis spectroscopy, and mass spectrometry, the formation of the azo dimer 4,4′-dimethoxyazobenzene was confirmed. However, due to the instability of the azo bond under the reducing conditions of our incubations, the azo dimer did not accumulate. Consequently, 4-aminoanisole was the major product formed in our experiment. Other minor suspected coupling products were also detected in our incubations. The results provide clear evidence for the temporal formation of at least one azo dimer in the anaerobic reduction of a model nitroaromatic compound.
KW - 2,4-Dinitroanisole (DNAN)
KW - Anaerobic biotransformation
KW - Azobenzenes
KW - Insensitive munitions compounds
KW - Nitroaromatics
UR - http://www.scopus.com/inward/record.url?scp=85038838558&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85038838558&partnerID=8YFLogxK
U2 - 10.1016/j.chemosphere.2017.12.083
DO - 10.1016/j.chemosphere.2017.12.083
M3 - Article
C2 - 29274576
AN - SCOPUS:85038838558
VL - 195
SP - 372
EP - 380
JO - Chemosphere
JF - Chemosphere
SN - 0045-6535
ER -