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Journal of Hazardous Materials May 2015Polyphenylene oxide (PPO) membranes synthesized from 2,6-dimethyl phenol monomer were subjected to pervaporation-based dehydration of the highly hazardous and hypergolic...
Polyphenylene oxide (PPO) membranes synthesized from 2,6-dimethyl phenol monomer were subjected to pervaporation-based dehydration of the highly hazardous and hypergolic monomethyl hydrazine (MMH) and unsymmetrical dimethyl hydrazine (UDMH) liquid propellants. Membranes were characterized by TGA, DSC and SEM to study the effect of temperature besides morphologies of surface and cross-section of the films, respectively. Molecular dynamics (MD) simulation was used to study the diffusion behavior of solutions within the membrane. CFD method was employed to solve the governing mass transfer equations by considering the flux coupling. The modeling results were highlighted by the experimental data and were in good agreement. High separation factors (35-70) and reasonable water fluxes (0.1-0.2 kg/m(2)h) were observed for separation of the aqueous azeotropes of MMH (35 wt%) and UDMH (20 wt%) and their further enrichment to >90% purity. Effect of feed composition, membrane thickness and permeate pressure on separation performance of PPO membranes were investigated to determine optimum operating conditions.
Topics: 1,2-Dimethylhydrazine; Aerosol Propellants; Algorithms; Calorimetry, Differential Scanning; Hazardous Substances; Hydrazines; Membranes, Artificial; Microscopy, Electron, Scanning; Models, Molecular; Monomethylhydrazine; Phenols; Polymers; Temperature; Water
PubMed: 25698568
DOI: 10.1016/j.jhazmat.2015.02.020 -
The Analyst Jan 2015A simple, highly selective and rapid gas chromatography method (packed column with flame ionization detection) has been developed to determine hydrazine and...
A simple, highly selective and rapid gas chromatography method (packed column with flame ionization detection) has been developed to determine hydrazine and monomethylhydrazine individually and for selective determination of hydrazine in the UH 25 mixture in organic medium. This method is based on the derivatization of hydrazine (at ambient temperature) with 1,1,1-trifluoro-4-(3-thienyl) (CF3 enone) in the absence of catalyst/buffer which leads to the formation of corresponding pyrazolidine/pyrazoline/pyrazole. The organic derivatives thus formed are then detected and their presence is confirmed by GC-MS. The GC method provides good resolution between CF3 enone and its derivatives with a total analysis time of 20 min. The concentration of CF3 enone and derivatization time are optimized to determine hydrazines in the concentration range of 0.4 mM to 0.2 M. The calibration curves based on peak areas of CF3 enone and its derivatives showed good linearity with r(2) ≈ 0.999 for the working range and the precision was found to be less than 1% for hydrazine, MMH and hydrazine in UH25. The recovery was found by the standard addition method. Under the established conditions, limits of detection were 20 μM for hydrazine, 10 μM for MMH and 20 μM for hydrazine in UH25. The tolerance limit for interfering amines was also found. The advantage of this method is the selective detection and determination of hydrazine in the UH25 mixture as 1,1-dimethylhydrazine present in UH25 cannot be derivatized with CF3 enone.
PubMed: 25386637
DOI: 10.1039/c4an01648c -
Bioorganic & Medicinal Chemistry Letters Sep 2014High throughput screening using Automated Ligand Identification System (ALIS) resulted in the discovery of a new series of S-adenosyl-L-homocysteine hydrolase inhibitors...
High throughput screening using Automated Ligand Identification System (ALIS) resulted in the discovery of a new series of S-adenosyl-L-homocysteine hydrolase inhibitors based on non-adenosine analogs. The optimization campaign led to very potent and competitive compound 39 with a Ki value of 1.5 nM. Compound 39 could be a promising lead compound for research to reduce elevated homocysteine levels.
Topics: Adenosine; Adenosylhomocysteinase; Amides; Amines; Dose-Response Relationship, Drug; Drug Discovery; Enzyme Inhibitors; High-Throughput Screening Assays; Humans; Molecular Structure; Monomethylhydrazine; Structure-Activity Relationship
PubMed: 25022879
DOI: 10.1016/j.bmcl.2014.06.008 -
Angewandte Chemie (International Ed. in... Feb 2013
Enantioselective synthesis of epoxides having a tetrasubstituted trifluoromethylated carbon center: methylhydrazine-induced aerobic epoxidation of β,β-disubstituted enones.
Topics: Alkenes; Carbon; Cyclic N-Oxides; Epoxy Compounds; Fluorine; Molecular Structure; Monomethylhydrazine; Oxygen; Stereoisomerism
PubMed: 23339133
DOI: 10.1002/anie.201209355 -
The Journal of Physical Chemistry. B Dec 2012To gain an atomistic-level understanding on physical and chemical processes occurring at the interfaces of hypergolic propellants, we carried out the first reactive...
To gain an atomistic-level understanding on physical and chemical processes occurring at the interfaces of hypergolic propellants, we carried out the first reactive dynamic (ReaxFF) simulations to study the reactive hypergolic mixture of monomethylhydrazine (MMH) and dinitrogen tetroxide (NTO), in comparison with the ethanol (EtOH) and NTO mixture that is reactive but nonhypergolic. Our studies show that the MMH-NTO mixture releases energy more rapidly than the EtOH-NTO mixture upon mixing the fuels and oxidizers. We found that the major early chemical reactions between MMH and NTO are hydrogen abstractions and N-N bond scissions. The MMH-NTO mixture has more reaction channels than EtOH-NTO based on statistical analyses of chemical reaction events and channels at early stages of the dynamics. Analyzing the evolution of product distribution over reaction time shows that the oxidizer (NO(2)) diffuses into the fuels (MMH or EtOH) for the occurrence of reactions, demonstrating the influence of physical mixing on chemical reactions. Our simulations suggest that effective hypergolic systems require fuels with low energy barriers of H abstractions and/or bond scissions and oxidizers with large diffusion mobility for efficient physical mixing.
PubMed: 23148488
DOI: 10.1021/jp308351g -
The Journal of Physical Chemistry. A Aug 2012The thermal decomposition of the CH(3)N(•)NH(2), cis-CH(3)NHN(•)H, trans-CH(3)NHN(•)H, and C(•)H(2)NNH(2) radicals, which are the four radical products from the...
The thermal decomposition of the CH(3)N(•)NH(2), cis-CH(3)NHN(•)H, trans-CH(3)NHN(•)H, and C(•)H(2)NNH(2) radicals, which are the four radical products from the H-abstraction reactions of monomethylhydrazine, were theoretically studied by using ab initio Rice-Ramsperger-Kassel-Marcus (RRKM) transition-state theory and master equation analysis. Various decomposition pathways were identified by using either the QCISD(T)/cc-pV∞Z//CASPT2/aug-cc-pVTZ or the QCISD(T)/cc-pV∞Z//B3LYP/6-311++G(d,p) quantum chemistry methods. The results reveal that the β-scission of NH(2) to form methyleneimine is the predominant channel for the decomposition of the C(•)H(2)NNH(2) radical due to its small energy barrier of 13.8 kcal mol(-1). The high pressure limit rate coefficient for the reaction is fitted by 3.88 × 10(19)T(-1.672) exp(-9665.13/T) s(-1). In addition, the pressure dependent rate coefficients exhibit slight temperature dependence at temperatures of 1000-2500 K. The cis-CH(3)NHN(•)H and trans-CH(3)NHN(•)H radicals are the two distinct spatial isomers with an energy barrier of 26 kcal mol(-1) for their isomerization. The β-scission of CH(3) from the cis-CH(3)NHN(•)H radical to form trans-diazene has an energy barrier of 35.2 kcal mol(-1), and the β-scission of CH(3) from the trans-CH(3)NHN(•)H radical to form cis-diazene has an energy barrier of 39.8 kcal mol(-1). The CH(3)N(•)NH(2) radical undergoes the β-scission of methyl hydrogen and amine hydrogen to form CH(2)═NNH(2), trans-CH(3)N═NH, and cis-CH(3)N═NH products, with the energy barriers of 42.8, 46.0, and 50.2 kcal mol(-1), respectively. The dissociation and isomerization rate coefficients for the reactions were calculated via the E/J resolved RRKM theory and multiple-well master equation analysis at temperatures of 300-2500 K and pressures of 0.01-100 atm. The calculated rate coefficients associated with updated thermochemical property data are essential components in the development of kinetic mechanisms for the pyrolysis and oxidation of MMH and its derivatives.
PubMed: 22813206
DOI: 10.1021/jp3045675 -
Molecules (Basel, Switzerland) May 2012Sixteen novel pyrazole acyl thiourea derivatives 6 were synthesized from monomethylhydrazine (phenylhydrazine) and ethyl acetoacetate. The key...
Sixteen novel pyrazole acyl thiourea derivatives 6 were synthesized from monomethylhydrazine (phenylhydrazine) and ethyl acetoacetate. The key 5-chloro-3-methyl-1-substituted-1H-pyrazole-4-carbonyl chloride intermediates 4 were first generated in four steps through cyclization, formylation, oxidation and acylation. Thess were then reacted with ammonium thiocyanate in the presence of PEG-400 to afford 5-chloro-3-methyl-1-substituted-1H-pyrazole-4-carbonyl isothiocyanates 5. Subsequent reaction with fluorinated aromatic amines resulted in the formation of the title compounds. The synthesized compound were unequivocally characterized by IR, ¹H-NMR, ¹³C-NMR and elemental analysis and some of the synthesized compounds displayed good antifungal activities against Gibberella zeae, Fusarium oxysporum, Cytospora mandshurica and anti-TMV activity in preliminary antifungal activity tests.
Topics: Acetoacetates; Acylation; Antifungal Agents; Antiviral Agents; Cyclization; Fusarium; Gibberella; Hydrocarbons, Fluorinated; Microbial Sensitivity Tests; Oxidation-Reduction; Phenylhydrazines; Polyethylene Glycols; Pyrazoles; Structure-Activity Relationship; Thiocyanates; Thiourea; Tobacco Mosaic Virus
PubMed: 22555301
DOI: 10.3390/molecules17055139 -
The Journal of Physical Chemistry. A May 2012The gas-phase kinetics of H-abstraction reactions of monomethylhydrazine (MMH) by OH radical was investigated by second-order multireference perturbation theory and...
The gas-phase kinetics of H-abstraction reactions of monomethylhydrazine (MMH) by OH radical was investigated by second-order multireference perturbation theory and two-transition-state kinetic model. It was found that the abstractions of the central and terminal amine H atoms by the OH radical proceed through the formation of two hydrogen bonded preactivated complexes with energies of 6.16 and 5.90 kcal mol(-1) lower than that of the reactants, whereas the abstraction of methyl H atom is direct. Due to the multireference characters of the transition states, the geometries and ro-vibrational frequencies of the reactant, transition states, reactant complexes, and product complexes were optimized by the multireference CASPT2/aug-cc-pVTZ method, and the energies of the stationary points of the potential energy surface were refined at the QCISD(T)/CBS level via extrapolation of the QCISD(T)/cc-pVTZ and QCISD(T)/cc-pVQZ energies. It was found that the abstraction reactions of the central and two terminal amine H atoms of MMH have the submerged energy barriers with energies of 2.95, 2.12, and 1.24 kcal mol(-1) lower than that that of the reactants respectively, and the abstraction of methyl H atom has a real energy barrier of 3.09 kcal mol(-1). Furthermore, four MMH radical-H(2)O complexes were found to connect with product channels and the corresponding transition states. Consequently, the rate coefficients of MMH + OH for the H-abstraction of the amine H atoms were determined on the basis of a two-transition-state model, with the total energy E and angular momentum J conserved between the two transition-state regions. In units of cm(3) molecule(-1) s(-1), the rate coefficient was found to be k(1) = 3.37 × 10(-16)T(1.295) exp(1126.17/T) for the abstraction of the central amine H to form the CH(3)N(•)NH(2) radical, k(2) = 2.34 × 10(-17)T(1.907) exp(1052.26/T) for the abstraction of the terminal amine H to form the trans-CH(3)NHN(•)H radical, k(3) = 7.41 × 10(-20)T(2.428) exp(1343.20/T) for the abstraction of the terminal amine H to form the cis-CH(3)NHN(•)H radical, and k(4) = 9.13 × 10(-21)T(2.964) exp(-114.09/T) for the abstraction of the methyl H atom to form the C(•)H(2)NHNH(2) radical, respectively. Assuming that the rate coefficients are additive, the total rate coefficient of these theoretical predictions quantitatively agrees with the measured rate constant at temperatures of 200-650 K, with no adjustable parameters.
PubMed: 22545789
DOI: 10.1021/jp3021529 -
Mutation Research Jul 2010Recognition of the occupational hazards from exposure to the propellants hydrazine and monomethylhydrazine (MMH) has led to research into less toxic alternatives. Two...
Recognition of the occupational hazards from exposure to the propellants hydrazine and monomethylhydrazine (MMH) has led to research into less toxic alternatives. Two hypergolic compounds, dimethylamino-2-ethylazide (DMAZ) and N,N,N',N'-tetramethylethanediamine (TMEDA), have been identified as possible replacements for MMH. We have obtained genotoxicity data for these compounds from in vitro and in vivo studies. DMAZ did not produce any mutagenic effects at concentrations up to 5mg/plate in the TA98 and TA1537 strains of Salmonella typhimurium and in an Escherichia coli (WP2 uvrA) strain, with or without metabolic activation, but did produce a positive response in the TA100 and TA1535 strains, both with and without metabolic activation. TMEDA was found not to be mutagenic in any of the bacterial strains tested (Salmonella TA98, TA100, TA1535, TA1537 and E. coli, WP2 uvrA), with or without metabolic activation. DMAZ did not induce structural chromosomal aberrations at levels up to 5mg/mL in Chinese hamster ovary (CHO) cells, with or without metabolic activation. TMEDA produced a positive response in this system, with or without metabolic activation, but only at the highest concentration, 5mg/mL. However, according to the OECD guideline TG 473, the compound is considered to be negative in the CHO chromosomal aberration assay, since the compound was not clastogenic at 0.01M (1.140mg/mL). DMAZ and TMEDA, when tested in vivo in the CD-1 mouse at doses up to 500 and 250mg/kg, respectively, did not induce micronuclei in bone marrow erythrocytes. These studies demonstrate that DMAZ is mutagenic in specific strains of Salmonella. However, both compounds were negative for induction of chromosomal aberrations in CHO cells in vitro and in the in vivo mouse micronucleus assay.
Topics: Animals; Azides; Biotransformation; CHO Cells; Chromosome Aberrations; Cricetinae; Cricetulus; DNA Damage; Diamines; Environmental Pollutants; Escherichia coli; Mice; Micronucleus Tests; Mutagenicity Tests; Mutagens; Occupational Exposure; Salmonella typhimurium
PubMed: 20417306
DOI: 10.1016/j.mrgentox.2010.04.019 -
Journal of Chromatographic Science Apr 2010Methylhydrazine (NH(2)NHCH(3), CAS 60-34-4) is a highly reactive reducing agent used as an intermediate for synthesizing an experimental drug substance. Methylhydrazine...
Methylhydrazine (NH(2)NHCH(3), CAS 60-34-4) is a highly reactive reducing agent used as an intermediate for synthesizing an experimental drug substance. Methylhydrazine is a known mutagen, an animal carcinogen, and a suspected human carcinogen. A gas chromatography-mass spectrometry method was developed as a limit test method for analyzing trace levels of methylhydrazine in the experimental drug substance. The method utilizes acetone as a dissolving solvent for the drug substance and a derivatizing agent for methylhydrazine in the meantime, thus eliminating the need for post-derivatization sample clean-up prior to analysis. The gas chromatographic (direct injection) conditions provide good separation for the acetone-methylhydrazine derivative (acetone methylhydrazone) from matrix interference, and mass spectrometric detection (selected ion monitoring mode, m/z 86) allows sufficient sensitivity for detecting 1 part per million methylhydrazine relative to the drug substance.
Topics: Acetone; Drug Contamination; Drug Stability; Gas Chromatography-Mass Spectrometry; Monomethylhydrazine; Pharmaceutical Preparations; Reproducibility of Results; Sensitivity and Specificity; Solid Phase Extraction; Temperature
PubMed: 20412653
DOI: 10.1093/chromsci/48.4.299