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Molecules (Basel, Switzerland) Nov 2020Recently discovered hybrid perovskites based on hypophosphite ligands are a promising class of compounds exhibiting unusual structural properties and providing...
Recently discovered hybrid perovskites based on hypophosphite ligands are a promising class of compounds exhibiting unusual structural properties and providing opportunities for construction of novel functional materials. Here, we report for the first time the detailed studies of phonon properties of manganese hypophosphite templated with methylhydrazinium cations ([CHNHNH][Mn(HPO)]). Its room temperature vibrational spectra were recorded for both polycrystalline sample and a single crystal. The proposed assignment based on Density Functional Theory (DFT) calculations of the observed vibrational modes is also presented. It is worth noting this is first report on polarized Raman measurements in this class of hybrid perovskites.
Topics: Calcium Compounds; Cations; Density Functional Theory; Ions; Manganese; Materials Testing; Microscopy, Confocal; Models, Molecular; Monomethylhydrazine; Oxides; Phosphites; Quantum Theory; Software; Spectrophotometry, Infrared; Spectroscopy, Fourier Transform Infrared; Spectrum Analysis, Raman; Temperature; Titanium; Vibration
PubMed: 33182446
DOI: 10.3390/molecules25215215 -
Military Medicine Feb 2021Hydrazines are highly toxic inorganic liquids that are used as propellants in military and aviation industries, such as the U.S. Air Force F-16 Emergency Power Unit and...
INTRODUCTION
Hydrazines are highly toxic inorganic liquids that are used as propellants in military and aviation industries, such as the U.S. Air Force F-16 Emergency Power Unit and SpaceX SuperDraco Rockets. The most commonly used derivatives include hydrazine, monomethylhydrazine, and 1,1-dimethylhydrazine (unsymmetrical dimethylhydrazine). Industrial workers in close contact with hydrazines during routine maintenance tasks can be exposed to levels well above the National Institute for Occupational Safety and Health relative exposure limits.
MATERIALS AND METHODS
A systematic review was performed using PubMed, Web of Science, Google Scholar, National Aeronautics and Space Administration Technical Server, and Defense Technical Information Center, and data related to hydrazine exposures were searched from inception to April 2020. Publications or reports addressing hydrazine toxicity, pathophysiology, and treatment of hydrazine fuel exposure were selected.
RESULTS
Acute toxic exposures to hydrazine and its derivatives are rare. There are few case reports of acute toxic exposure in humans, and data are largely based on animal studies. The initial search identified 741 articles, manuscripts, and government reports. After screening for eligibility, 51 were included in this review. Eight articles reported acute exposures to hydrazine propellant in humans, and an additional 14 articles reported relevant animal data.
CONCLUSIONS
Exposure to small amounts of hydrazine and its derivatives can cause significant soft tissue injury, pulmonary injury, seizures, coma, and death. Neurologic presentations can vary based on exposure compound and dose. Decontamination is critical as treatment is mainly supportive. High-dose intravenous pyridoxine has been suggested as treatment for hydrazine-related neurologic toxicity, but this recommendation is based on limited human data. Despite recent research efforts to generate less toxic alternatives to hydrazine fuel, it will likely continue to have a role in military and aviation industries. Aerospace and military physicians should be aware of the toxicity associated with hydrazine exposure and be prepared to treat hydrazine toxicity in at-risk populations.
Topics: Animals; Aviation; Humans; Hydrazines; Military Personnel; United States
PubMed: 33175959
DOI: 10.1093/milmed/usaa429 -
Chemistry, An Asian Journal Dec 2020Functionalized hydrazines and bishydrazines are interesting straightforward precursors for accessing higher nitrogenated compounds. They offer structural diversity and...
Functionalized hydrazines and bishydrazines are interesting straightforward precursors for accessing higher nitrogenated compounds. They offer structural diversity and promising energetic properties as well, namely for propulsion applications. A novel and scalable synthesis has been developed for a new family of bishydrazines, starting from monomethylhydrazine (MMH). This solvent-free route represents a suitable alternative to the one described in the literature. It was extended to design a new family of unsymmetrical hydrazines bearing various functional groups. A selected series of promising compounds, densified with nitrogenated groups (amino, hydrazino or azido functions), was identified as a class of plausible candidates for liquid propulsion. Indeed, the energetic interest of such hydrazines was demonstrated by computing their heats of formation and specific impulse values in bipropellant systems. This led to theoretical energetic performances comparable to that of the MMH/N O system already in use today.
PubMed: 33155765
DOI: 10.1002/asia.202001084 -
The Journal of Physical Chemistry. A Jul 2020Experimental, numerical, and theoretical studies are performed to understand the explosive thermal decomposition of monomethylhydrazine/argon mixtures. Ignition delays...
Experimental, numerical, and theoretical studies are performed to understand the explosive thermal decomposition of monomethylhydrazine/argon mixtures. Ignition delays of concentrated MMH/Ar mixtures (20-30%) have been measured behind a reflected shock wave around 1000 K and 1 atm. Although several detailed chemical kinetic models have predictive abilities for diluted and highly diluted mixtures, none of them showed predictive for concentrated mixtures. A new kinetic model is proposed, in which numerous rate constants and thermochemical data are reassessed based on theoretical calculations, with the purpose to determine whether, or to what extent, trends derived from diluted or highly diluted MMH/Ar mixtures can explain observations in concentrated MMH mixtures. The present kinetic model is found to predict speciation experimental profiles in diluted MMH/Ar mixtures and is a significant improvement in predicting the induction delays of concentrated MMH/Ar mixtures.
PubMed: 32603112
DOI: 10.1021/acs.jpca.0c03144 -
The Journal of Physical Chemistry. A May 2020Methylamine radicals (CHNH) and amino radicals (NH) are major products in the early pyrolysis/ignition of monomethylhydrazine (CHNHNH). kinetics of thermal...
Methylamine radicals (CHNH) and amino radicals (NH) are major products in the early pyrolysis/ignition of monomethylhydrazine (CHNHNH). kinetics of thermal decomposition of CHNH radicals was analyzed by RRKM master equation simulations. It was found that β-scission of the methyl H-atom from CHNH radicals is predominant and fast enough to induce subsequent H-abstraction reactions in CHNHNH to trigger ignition. Consequently, the kinetics of H-abstraction reactions from CHNHNH by H-atoms was further investigated. It was found that the energy barriers for abstraction of the central amine H-atom, two terminal amine H-atoms, and methyl H-atoms are 4.16, 2.95, 5.98, and 8.50 kcal mol, respectively. In units of cm molecule s, the corresponding rate coefficients were found to be = 9.63 × 10 exp(-154.2/), = 2.04 × 10 exp(104.1/), = 1.13 × 10 exp(-416.3/), and = 2.41 × 10 exp(-870.5/), respectively, in the 290-2500 K temperature range. The results reveal that abstraction of the terminal amine H-atom to form -CHNHNH radicals is the dominant channel among the different abstraction channels. At 298 K, the total theoretical H-abstraction rate coefficient, calculated with no adjustable parameters, is 8.16 × 10 cm molecule s, which is in excellent agreement with Vaghjiani's experimental observation of (7.60 ± 1.14) × 10 cm molecule s ( 1997, 101, 4167-4171, DOI: 10.1021/jp964044z).
PubMed: 32299215
DOI: 10.1021/acs.jpca.0c02389 -
The Journal of Physical Chemistry... May 2019The exploration of chemical reactions preceding ignition is essential for the development of ideal hypergolic propellants. Unexpected reaction pathways of a hypergolic...
The exploration of chemical reactions preceding ignition is essential for the development of ideal hypergolic propellants. Unexpected reaction pathways of a hypergolic mixture composed of monomethylhydrazine and nitrogen dioxide are predicted through a cooperative combination of (i) spin-unrestricted ab initio molecular dynamics (AIMD) and (ii) wave packet dynamics of protons. Ensembles of AIMD trajectories reveal a sequence of reaction steps for proton transfer and rupture of the C-N bond. The details of proton transfer are explored by wave packet dynamics on the basis of ab initio potential energy surfaces from AIMD trajectories. The possibility of spontaneous ignition of this hypergolic mixture at room temperature is predicted as a quantized feature of proton-transfer dynamics.
PubMed: 30978025
DOI: 10.1021/acs.jpclett.9b00674 -
Mycologia 2018Ingestion of wild and potentially toxic mushrooms is common in the United States and many other parts of the world. US poison centers have been logging cases of mushroom...
Ingestion of wild and potentially toxic mushrooms is common in the United States and many other parts of the world. US poison centers have been logging cases of mushroom exposure in The National Poison Data System (NPDS) annual publications for over 30 years. This study compiles and analyzes US mushroom exposures as reported by the NPDS from 1999 to 2016. Over the last 18 years, 133 700 cases (7428/year) of mushroom exposure, mostly by ingestion, have been reported. Cases are most frequently unintentional (83%, P < 0.001); cause no or only minor harm (86%, P < 0.001); and in children <6 years old (62%, P < 0.001). Approximately 704 (39/year) exposures have resulted in major harm. Fifty-two (2.9/year) fatalities have been reported, mostly from cyclopeptide (68-89%)-producing mushrooms ingested by older adults unintentionally. The vast majority of reported ingestions resulted in no or minor harm, although some groups of mushroom toxins or irritants, such as cyclopepides, ibotenic acid, and monomethylhydrazine, have been deadly. Misidentification of edible mushroom species appears to be the most common cause and may be preventable through education.
Topics: Adolescent; Adult; Agaricales; Child; Child, Preschool; Data Analysis; Female; Humans; Male; Mushroom Poisoning; Mycotoxins; Poison Control Centers; Psilocybin; United States; Young Adult
PubMed: 30062915
DOI: 10.1080/00275514.2018.1479561 -
Toxicology in Vitro : An International... Oct 2018Hydrazine-based liquid propellants are routinely used for space rocket propulsion, in particular monomethylhydrazine (MMH), although such compounds are highly hazardous....
Hydrazine-based liquid propellants are routinely used for space rocket propulsion, in particular monomethylhydrazine (MMH), although such compounds are highly hazardous. For several years, great efforts were devoted to developing a less hazardous molecule. To explore the toxicological effects of an alternative compound, namely (E)-1,1,4,4-tetramethyl-2-tetrazene (TMTZ), we exposed various cellular animal and human models to this compound and to the reference compound MMH. We observed no cytotoxic effects following exposure to TMTZ in animal, as well as human models. However, although the three animal models were unaffected by MMH, exposure of the human hepatic HepaRG cell model revealed that apoptotic cytotoxic effects were only detectable in proliferative human hepatic HepaRG cells and not in differentiated cells, although major biochemical modifications were uncovered in the latter. The present findings indicate that the metabolic mechanisms of MMH toxicity is close to those described for hydrazine with numerous biochemical alterations induced by mitochondrial disruption, production of radical species, and aminotransferase inhibition. The alternative TMTZ molecule had little impact on cellular viability and proliferation of rodent and human dermic and hepatic cell models. TMTZ did not produce any metabolomic effects and appears to be a promising putative industrial alternative to MMH.
Topics: Aerosol Propellants; Animals; Azo Compounds; Cell Line; Cell Survival; Cricetulus; Fibroblasts; Humans; Metabolomics; Mice; Monomethylhydrazine
PubMed: 29885439
DOI: 10.1016/j.tiv.2018.06.005 -
Chemistry (Weinheim An Der Bergstrasse,... Jul 20171,1,4,4-Tetramethyl-2-tetrazene (TMTZ) is considered as a prospective replacement for toxic hydrazines used in liquid rocket propulsion. The heat of formation of TMTZ...
1,1,4,4-Tetramethyl-2-tetrazene (TMTZ) is considered as a prospective replacement for toxic hydrazines used in liquid rocket propulsion. The heat of formation of TMTZ was computed and measured, giving values well above those of the hydrazines commonly used in propulsion. This led to a predicted maximum I of 337 s for TMTZ/N O mixtures, which is a value comparable to that of monomethylhydrazine. We found that TMTZ has a vapor pressure well below that of liquid hydrazines, and it is far less toxic. Finally, an improved synthesis is proposed, which is compatible with existing industrial production facilities after minor changes. TMTZ is thus an attractive liquid propellant candidate, with a performance comparable to hydrazines but a lower vapor pressure and toxicity.
PubMed: 28498558
DOI: 10.1002/chem.201701468 -
Organic & Biomolecular Chemistry Sep 2015We herein present the first in-depth theoretical study devoted to elucidate the mechanism of the reaction between 1,2,4-oxadiazole derivatives and methylhydrazine. For...
We herein present the first in-depth theoretical study devoted to elucidate the mechanism of the reaction between 1,2,4-oxadiazole derivatives and methylhydrazine. For this purpose, the reaction between methylhydrazine and some polyfluoroaryl-1,2,4-oxadiazoles has been employed as a model reaction. The analysis of the potential energy surface (PES) indicates that the most favorable path involves an initial amine attack at the C(2') site of the aryl moiety to yield an aryl-hydrazine intermediate whose thermodynamic stability appears as the main determinant of the favored reaction path. Next, the cyclization step leading to a spiro intermediate through a favored 5-exo-trig process appears as the rate determining step. Additionally, this study highlights the relevance of the torsional strain effects on the favored ANRORC pathway. Finally, both the origins of the substituent effects on the regioselectivity patterns as well as the need of using a large excess of nucleophile to afford the favored ANRORC pathway are discussed.
Topics: Molecular Structure; Monomethylhydrazine; Oxadiazoles; Quantum Theory
PubMed: 26247805
DOI: 10.1039/c5ob01300c