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.
Characterization and Fate of N-Nitrosodimethylamine Precursors in Municipal Wastewater Treatment Plants
Mitch, William A.,Sedlak, David L.
, p. 1445 - 1454 (2004)
The potent carcinogen, N-nitrosodimethylamine (NOMA), is produced during disinfection of municipal wastewater effluent from the reaction of monochloramine and organic nitrogen-containing precursors. To delineate the sources and fate of NDMA precursors during municipal wastewater treatment, NDMA formation was measured after extended chloramination of both model precursors and samples from conventional and advanced wastewater treatment plants. Of the model precursors, only dimethylamine, tertiary amines with dimethylamine functional groups, and dimethylamides formed significant NDMA concentrations upon chloramination. In samples from municipal wastewater treatment plants, dissolved NDMA precursors always were present in primary and secondary effluents. Biological treatment effectively removed the known NDMA precursor dimethylamine, lowering its concentration to levels that could not produce significant quantities of NDMA upon chlorine disinfection. However, biological treatment was less effective at removing other dissolved NDMA precursors, even after extended biological treatment. Significant concentrations of particle-associated NDMA precursors only were detected in secondary effluent at treatment plants that recycled water from sludge thickening operations in which dimethylamine-based synthetic polymers were used. Effective strategies for the prevention of NDMA formation during wastewater chlorination include ammonia removal by nitrification to preclude chloramine formation during chlorine disinfection, elimination of dimethylamine-based polymers, and use of filtration and reverse osmosis to remove particle-associated precursors and dissolved precursors, respectively.
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
Infrared Multiphoton Decomposition of Dimethylnitramine
Lazarou, Yannis G.,Papagiannakopoulos, Panos
, p. 7114 - 7119 (1990)
The infrared multiphoton dissociation of dimethylnitramine in the gas phase by a pulsed CO2 laser has been studied in order to elucidate its photochemical decomposition mechanism under collisionless conditions and provide a qualitative understanding of the consequent chemical mechanism that leads to the final products.The experimentally determined steady-state rate coefficient for the unimolecular decomposition of dimethylnitramine was found to be k(st) = 105.5+/-0.1 (I/MW cm-2)s-1 for laser intensities 2-10 MW cm-2.Scavenging experiments with Cl2, NOCl, NO,NO2, and (CD3)2NNO2 molecules have shown that the decomposition dynamics proceeds through scission of the N-NO2 bond, with no evidence of the HONO elimination or the isomerization to nitro-nitrite channel.Dimethylnitrosamine was the major final product which was mainly produced through oxidation of dimethylamino radical by dimethylnitramine.
Kinetic Studies on the Formation of N-Nitroso Compounds XI. Nitrosation of Dimethylamine with Nitrite Esters in Aqueous Basic Media
Casado, Julio,Castro, Albino,Lorenzo, Francisco M.,Meijide, Francisco
, p. 335 - 344 (1986)
A kinetic study of the mechanism of the nitrosation of dimethylamine (DMA) by propyl nitrite (PrONO) in basic media to yield N-nitrosodimethylamine (NDMA) has found the rate equation to be ν=d/dt=k2/(1++>/K1) where and are total concentrations.At 298.2 K and I=0.25 M, k2=(6.59+/-0.13)*1E-2 M-1s-1 and K1=(1.16+/-0.07)*1E-11 M.The observed influence of ionic strength, the kinetic results obtained in water/tetrahydrofuran mixtures and in heavy water (kH/kD=2.09), and the value of ΔS(excit.)(-158 JK-1mol-1) suggest that the nitrosating agent PrONO attacks the free amine to create a tetracentric transition state and that this is the rate controlling step of the reaction.Experiments carried out with other nitrite esters have shown there to be a correlation satisfying Taft's equation between their structure and their reactivity with DMA (ρ*=3.89), which allows the rate constant for nitrous acid to be calculated. - Keywords: Dimethylamine; Kinetics of nitrosation; Nitrite esters; N-Nitrosodimethylamine
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
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.
Adsorption and photocatalytic degradation of gas-phase UDMH under simulated sunlight by AgBr/TiO2/rGA
Ruomeng, Hou,Ying, Jia,Xiaomeng, Lv,Yuanzheng, Huang,Keke, Shen
, p. 12583 - 12594 (2021/04/14)
The degradation of UDMH has long been a concern for its harmful effects on humans and the environment. The current research on gas-phase UDMH treatment is limited and mainly focuses on ultraviolet light and high temperature environments, however the highly toxic substance NDMA is easily produced. In order to investigate the possibility of UDMH degradation in sunlight, AgBr/TiO2/rGA composites were prepared with the addition of different amounts of silver bromide. The highest UDMH conversion of AgBr/TiO2/rGA in humid air is 51%, much higher than the control group value of 24%, which can be ascribed to the synergy of adsorption and photocatalysis. The graphene and silver in AgBr/TiO2/rGA not only enhance the adsorption of light and UDMH, but also inhibit charge recombination and enhance electron-hole separation. More importantly, the temperature of the AgBr/TiO2/rGA composite was raised by the photothermal effect of graphene with promoted UDMH degradation efficiency. Furthermore, it is noted that NDMA was not detected in the optimal conditions.
Preparation method of PI3K inhibitor
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Paragraph 0062-0064, (2020/08/02)
The invention provides a preparation method of a PI3K inhibitor. The PI3K inhibitor is (S)-2-[1-(9H-purine-6-ylamino) ethyl]-3-(dimethylamino)-5-fluoroquinazoline-4 (3H)-ketone, and the structural formula of the PI3K inhibitor is shown in the specification. The method comprises three steps of reactions. The method has the advantages of simple reaction steps, mild reaction conditions, indiscriminate application of the solvent, economy and environmental protection. The PI3K inhibitor is subjected to optical purification and salifying crystallization refining through organic acid resolution and has simplicity in operation, improved yield, low cost and more stable batch-to-batch quality in comparison with present silica gel column chromatography and preparation separation and is suitable for industrial production.
