62-75-9Relevant articles and documents
Formation of N-nitrosodimethylamine (NDMA) from dimethylamine during chlorination
Mitch, William A.,Sedlak, David L.
, p. 588 - 595 (2002)
Chlorine disinfection of secondary wastewater effluent and drinking water can result in the production of the potent carcinogen N-nitrosodimethylamine (NDMA) at concentrations of approximately 100 and 10 parts per trillion (ng/L), respectively. Laboratory experiments with potential NDMA precursors indicate that NDMA formation can form during the chlorination of dimethylamine and other secondary amines. The formation of NDMA during chlorination may involve the slow formation of 1,1-dimethylhydrazine by the reaction of monochloramine and dimethylamine followed by its rapid oxidation to NDMA and other products including dimethylcyanamide and dimethylformamide. Other pathways also lead to NDMA formation during chlorination such as the reaction of sodium hypochlorite with dimethylamine. However, the rate of NDMA formation is approximately an order of magnitude slower than that observed when monochloramine reacts with dimethylamine. The reaction exhibits a strong pH dependence due to competing reactions. It may be possible to reduce NDMA formation during chlorination by removing ammonia prior to chlorination, by breakpoint chlorination, or by avoidance of the use of monochloramine for drinking water disinfection.
Oxidation of citalopram with sodium hypochlorite and chlorine dioxide: Influencing factors and NDMA formation kinetics
Lv, Juan,Wang, Yan,Li, Na
, (2019)
The highly prescribed antidepressant, citalopram, as one of newly emerging pollutants, has been frequently detected in the aquatic environment. Citalopram oxidation was examined during sodium hypochlorite (NaOCl) and chlorine dioxide (ClO2) chlorination processes since conventional wastewater treatment plants cannot remove citalopram effectively. Citalopram has been demonstrated to form N-nitrosodimethylamine (NDMA) during chlorination in our previous study. Further investigation on NDMA formation kinetics was conducted in the present study. Influences of operational variables (disinfectant dose, pH value) and water matrix on citalopram degradation, as well as NDMA generation, were evaluated. The results indicated high reactivity of citalopram with NaOCl and ClO2. NDMA formation included two stages during CIT oxidation, which were linear related with reaction time. NaOCl was more beneficial to remove CIT, but it caused more NDMA formation. Increasing disinfectant dosage promoted citalopram removal and NDMA formation. However, no consistent correlation was found between citalopram removal and pH. Contrary to the situation of citalopram removal, NDMA generation was enhanced when citalopram was present in actual water matrices, especially in secondary effluent. DMA, as an intermediate of citalopram chlorination, contributed to NDMA formation, but not the only way.
Formation of N-nitrosodimethylamine (NDMA) from reaction of monochloramine: A new disinfection by-product
Choi, Junghoon,Valentine, Richard L.
, p. 817 - 824 (2002)
Studies have been conducted specifically to investigate the hypothesis that N-nitrosodimethylamine (NDMA) can be produced by reactions involving monochloramine. Experiments were conducted using dimethylamine (DMA) as a model precursor. NDMA was formed from the reaction between DMA and monochloramine indicating that it should be considered a potential disinfection by-product. The formation of NDMA increased with increased monochloramine concentration and showed maximum in yield when DMA was varied at fixed monochloramine concentrations. The mass spectra of the NDMA formed from DMA and 15N isotope labeled monochloramine (15NH2Cl) showed that the source of one of the nitrogen atoms in the nitroso group in NDMA was from monochloramine. Addition of 0.05 and 0.5mM of preformed monochloramine to a secondarily treated wastewater at pH 7.2 also resulted in the formation of 3.6 and 111ng/L of NDMA, respectively, showing that this is indeed an environmentally relevant NDMA formation pathway. The proposed NDMA formation mechanism consists of (i) the formation of 1,1-dimethylhydrazine (UDMH) intermediate from the reaction of DMA with monochloramine followed by, (ii) the oxidation of UDMH by monochloramine to NDMA, and (iii) the reversible chlorine transfer reaction between monochloramine and DMA which is parallel to (i). We conclude that reactions involving monochloramine in addition to classical nitrosation reactions are potentially important pathways for NDMA formation. Copyright
PULSED LASER PYROLYSIS OF DIMETHYLNITRAMINE AND DIMETHYLNITROSAMINE
McMillen, Donald F.,Nigenda, S. Esther,Gonzalez, Alicia C.,Golden, David M.
, p. 237 - 240 (1987)
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Degradation of gaseous unsymmetrical dimethylhydrazine by vacuum ultraviolet coupled with MnO2
Huang, Yuanzheng,Jia, Ying,Shen, Keke,Hou, Ruomeng,Zhang, Yongyong,Hou, Li'an
supporting information, p. 1194 - 1202 (2021/02/06)
In this study, α-, β-, and δ-MnO2 were prepared by a uniform hydrothermal method and then coupled with vacuum ultraviolet (VUV) for the degradation of gaseous unsymmetrical dimethylhydrazine (UDMH). The performance in the removal of UDMH, by-product distribution and mechanism were systematically investigated. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption/desorption, Field Emission Scanning Electron Microscopy (FE-SEM), Raman, thermogravimetry (TG), Fourier-transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) to investigate the factors affecting the catalytic activity. The results showed that O2 and H2O were essential for the removal of UDMH. Photooxidation and ozone catalytic oxidation contribute to the removal and mineralization of UDMH. The integrated process considerably improved the removal and mineralization of UDMH by ozone catalytic oxidation. More reactive oxygen species were generated in the integrated process. The catalytic activity of the prepared catalysts follows the order: δ-MnO2 > α-MnO2 > β-MnO2. δ-MnO2 displayed the highest removal rate of 100% and a CO2 concentration of 42 ppmv. The good performance of δ-MnO2 was mainly attributed to the large number of surface oxygen vacancies.
TiO2-reduced graphene oxide for the removal of gas-phase unsymmetrical dimethylhydrazine
Ruomeng, Hou,Ying, Jia,Yuanzheng, Huang,Keke, Shen,Huixin, Zhu
, p. 394 - 402 (2021/01/11)
Unsymmetrical dimethylhydrazine (UDMH) contaminated waste gas and related intermediates pose a great threat to human health. TiO2-reduced graphene oxide aerogel (rGA) samples with different graphene content levels were synthetized and characterized for the degradation of UDMH. The effects of GO content, humidity, and temperature were investigated under UV and VUV light, with highest UDMH conversion values of 68% and 95%, respectively. Compared with pure TiO2, the enhanced degradation activity of TiO2-rGA under UV light can be attributed to a synergetic effect between absorption and photocatalysis, while the high UDMH conversion under VUV light relies on photolysis and ozonation. The high oxygen-containing group content, rather than a high SSA, and electron trapping by graphene are key factors determining the outstanding performance of TiO2-rGA with 80 mg of GO. The prepared TiO2-graphene aerogels are promising for the degradation of gas-phase UDMH. This journal is
Identification of unexpected unlabeled N,N-dimethylamide formation in the synthesis of deuterated fragment of ribociclib by a HATU-mediated coupling reaction
Gai, Kuo,Liu, Baomin,Zhang, Yinsheng
, p. 62 - 66 (2018/11/27)
Starting from N,N-dimethylamine and D2O, deuterated fragment of ribociclib was synthesized for use as a mass spectroscopy internal standard. Furthermore, systematic studies on D0 (unlabeled material) formation during the amidation reaction were performed, leading to the identification of a coupling reagent, HATU (O-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate), as main cause. Finally, an alternative route was designed using EDCI/HOBT as coupling reagents to produce the desired deuterated compound without D0 residue.
