Gaseous Methylamine Research Articles

Contribution of marine biological emissions to gaseous methylamines in the atmosphere: An emission inventory based on multi-source data sets

Methylamines are a class of highly reactive organic alkaline gases in the atmosphere. At present, the gridded emission inventories of amines used in the atmospheric numerical model is mostly based on the amine/ammonia ratio method and do not consider the air-sea exchange of methylamines, which oversimplifies the emission scenario. Marine biological emissions (MBE), an important source of methylamines, has been insufficiently investigated. These shortcomings in the inventories can limit the simulation of amines by numerical models in the context of compound pollution in China. To acquire a more complete gridded inventory of amines (monomethylamine (MMA), dimethylamines (DMA), and trimethylamines (TMA)), we established a more reasonable MBE inventory of amines by using multi-source data sets (Sea Surface Temperature (SST), Chlorophyll-a (Chla), Sea Surface Salinity (SSS), NH3 column concentration (NH3), and Wind Speed (WS)), and merged it with the anthropogenic emissions (AE) inventory (by adopting the amine/ammonia ratio method and the Multi-resolution Emission Inventory for China (MEIC)). The new methodology can reveal the air-sea exchange fluxes and direction of different amines. Oceans can act as a sink for DMA and source for TMA while it can be either a source or sink for MMA. The concentration of amines above the coastal area increased significantly when the MBE was merged to the AE inventory. TMA and MMA showed significant increases, TMA increased by 43,917.0 %, and 804.0 %, in July 2015 and December 2019, respectively; while MMA increased by 2635.4 % and 0.37 % during the same periods; however, only slight changes were observed in the DMA concentration (−3.9 % in July 2015, and 1.1 % in December 2019). WS, Chla, and the total dissolved concentration of amines ([C+(s)tot]) were found to be the dominant factors affecting MBE fluxes. In addition, the emission fluxes and spatial distribution of AE, and wet deposition also affect the simulation of amines concentration.

Discovery of N-methylbenzo[d]oxazol-2-amine as new anthelmintic agent through scalable protocol for the synthesis of N-alkylbenzo[d]oxazol-2-amine and N-alkylbenzo[d]thiazol-2-amine derivatives

We discovered a lead compound, N-methylbenzo[d]oxazol-2-amine (2a), which had comparable potency to albendazole, an orally administered anthelminticdrug, against Gnathostoma spinigerum, Caenorhabditis elegans and Trichinella spiralis. Compound 2a showed about 10 times lower cytotoxicity towards normal human cell line (HEK293) than albendazole. Moreover, we have developed new processes for the synthesis of N-alkylbenzo[d]oxazol-2-amine and N-alkylbenzo[d]thiazol-2-amine derivatives via metal-free conditions. This protocol could serve as a robust and scalable method, especially, to synthesize N-methylbenzo[d]oxazol-2-amine and N-methylbenzo[d]thiazol-2-amine derivatives which were difficult to prepare using other metal-free conditions. The method employed benzoxazole-2-thiol or benzothiazole-2-thiol as the substrate. The reaction was triggered by methylation of the thiol functional group to form the methyl sulfide intermediate, a crucial tactic, which facilitated in a smooth nucleophilic addition–elimination reaction with gaseous methylamine generated in situ from N-methylformamide. In addition, the proteomic analysis of compound 2a was also studied in this work.

Simultaneous measurement of methylamine in size-segregated aerosols and the gas phase

In order to improve our understanding of the origin and production processes of methylamine in the atmosphere and its contribution to the particulate WSON, simultaneous measurements of methylamine in size-segregated aerosols and the gas phase were conducted at a forested site in Yamanashi Prefecture, Japan, over one year. The concentration of the atmospheric methylamine that is the sum of methylamine in the gas phase, coarse-mode, and fine-mode particles was 0.962 ng-N m−3 on average. About 77% of the atmospheric methylamine was detected in the fine-mode particles and about 17% was in the gas phase. Similar seasonal variations were found in the fine-mode and gaseous methylamine including higher concentrations recorded in summer. The relationship between the concentrations of the gaseous methylamine and ammonia showed a significant positive correlation, suggesting that methylamine in the gas phase has similar sources with ammonia; for instance, the volatilization from soil and/or emission from forest biological activities. The concentration of the fine-mode methylamine showed a significant positive correlation with that of the gaseous methylamine, and the concentration ratio of the fine-mode methylamine to the sum of the fine-mode and gaseous methylamine that can be an indicator of the conversion of methylamine from the gas phase to the particulate phase showed a significant positive correlation with the fine-mode non-sea salt SO4 2- (nss-SO4 2-) concentration, suggesting that the gaseous methylamine is converted into the particulate methylamine through the acid-base reaction with sulfuric acid and/or nss-SO4 2-. Significant positive correlation was not obtained in the comparison of the concentration ratio of the fine-mode methylamine to the sum of the fine-mode and gaseous methylamine with the excessive amount of sulfuric acid for complete neutralization of ammonia, which implies the possibility that the sulfuric acid more preferentially reacts with the gaseous methylamine than ammonia.

Degradation Mechanisms in Organic Lead Halide Perovskite Light‐Emitting Diodes

AbstractOrganic–inorganic metal halide perovskites have attracted significant attention for low‐cost, high‐efficiency, color‐pure light‐emitting applications. However, as seen in many reports so‐far, perovskite light‐emitting diodes (PeLED) suffer from poor operational lifetime, limiting their practical use. The underlying degradation mechanism is a topic of crucial importance. Here, the degradation mechanisms of methylammonium lead bromide based PeLED are investigated. When the PeLED is electrically biased, there is an initial raise in the luminance followed by a rapid reduction in luminance and current density. Microscopic studies reveal the formation of micrometer‐sized spots that are photoluminescent but not electroluminescent. It is demonstrated that this degradation is due to the formation of gaseous compounds that leads to local delamination of the cathode, thereby reducing the electroluminescence. When the degraded cathode is substituted with a fresh cathode, the initial luminance is largely recovered. By further analyzing the buried interface of the cathode, the formation of lead bromide and gaseous methylamine due to the degradation of the perovskite layer are revealed. These insights will help to further improve the lifetime of PeLEDs. As an example, it is shown that substituting methylammonium cations by cesium leads to longer lifetimes.

Measurement of methylamines in seawater using solid phase microextraction and gas chromatography

AbstractThe methylamines form part of the marine organic nitrogen pool. Although they are ubiquitous in marine systems, little is known about their distribution, production, and fate in the marine environment. Analytical methods have been developed for their analysis in marine waters, but these have employed custom‐made apparatus, limiting data to a few studies. Here, we report a method developed for the determination of methylamines in seawater which combines headspace solid phase microextraction (SPME) and gas chromatography with selective nitrogen detection. Gaseous methylamines were pre‐concentrated from water samples (∼ 1 L) heated to 60 °C, onto a polydimethylsiloxane/divinylbenzene SPME fiber located in the headspace of the extraction flask. The analytes were then thermally desorbed from the fiber in a gas chromatograph containing a CP‐Volamine column and a nitrogen–phosphorus detector. The method was routinely calibrated down to 1 nM for all three analytes using matrix‐matched external standards. Limits of detection were determined operationally and ranged from 0.4 nM to 2.9 nM during two sampling campaigns. The analytes were detected in seawater samples from the English Channel and Southern Ocean where concentrations up to 20 nM and 5.6 nM were measured, respectively, consistent with previously reported levels. We propose this method for the analysis of methylamines, and other low‐molecular weight amines, as it is sensitive, robust, and the necessary equipment is widely available.

High-resolution modeling of gaseous methylamines over a polluted region in China: source-dependent emissions and implications of spatial variations

Abstract. Amines have received increasing attention in recent years because of their potential role in new particle formation in the atmosphere and their impact on aerosol chemistry. High concentrations of amines are expected to be limited to the vicinity of source regions due to their short lifetime, highlighting the necessity of having a better understanding of contributions of emissions from different source types. This study presents the first high-resolution model simulation of concentrations of methylamines on a regional scale over the Yangtze River Delta region in East China. The WRF-Chem with nested grids is used in model simulations. In contrast to the very limited existing modeling studies that assumed a fixed ratio (FR) of amines to total ammonia emission, we derive source-dependent ratios (SDR) that distinguish C1-amine (CH3NH2), C2-amines (C2H7N), C3-amines (C3H9N) emissions from five different source types (agriculture, residential, transportation, chemical industry, and other industry). The amines-to-ammonia mass emission ratios, estimated from previous measurements, are 0.026, 0.0015, 0.0011, 0.0011, and 0.0011 for C1-amine; 0.007, 0.0018, 0.0015, 0.01, and 0.0009 for C2-amines; and 0.0004, 0.0005, 0.00043, 0.0006, and 0.0004 for C3-amines for chemical–industrial, other industrial, agricultural, residential, and transportational sources, respectively. The simulated concentrations of C1-, C2-, and C3-amines, based on both FR and SDR, have been compared with field measurements at a suburban site in Nanjing and at an urban site in Shanghai, China. SDR substantially improves the ability of the model in capturing the observed concentrations of methylamines. Concentrations of C1-, C2-, and C3-amines in the surface layer in the Yangtze River Delta region are generally in the range of 2–20, 5–50, and 0.5–4 pptv. Vertically, the concentrations of C1-, C2-, and C3-amines decrease quickly with altitude, dropping by a factor of ∼10 from the surface to ∼900 hPa. Results from the present study are critical to evaluating potential roles of amines in nucleation and chemical processes in polluted air.

On the Thermal and Thermodynamic (In)Stability of Methylammonium Lead Halide Perovskites.

The interest of the scientific community on methylammonium lead halide perovskites (MAPbX3, X = Cl, Br, I) for hybrid organic-inorganic solar cells has grown exponentially since the first report in 2009. This fact is clearly justified by the very high efficiencies attainable (reaching 20% in lab scale devices) at a fraction of the cost of conventional photovoltaics. However, many problems must be solved before a market introduction of these devices can be envisaged. Perhaps the most important to be addressed is the lack of information regarding the thermal and thermodynamic stability of the materials towards decomposition, which are intrinsic properties of them and which can seriously limit or even exclude their use in real devices. In this work we present and discuss the results we obtained using non-ambient X-ray diffraction, Knudsen effusion-mass spectrometry (KEMS) and Knudsen effusion mass loss (KEML) techniques on MAPbCl3, MAPbBr3 and MAPbI3. The measurements demonstrate that all the materials decompose to the corresponding solid lead (II) halide and gaseous methylamine and hydrogen halide, and the decomposition is well detectable even at moderate temperatures (~60 °C). Our results suggest that these materials may be problematic for long term operation of solar devices.

Modeling of gaseous methylamines in the global atmosphere: impacts of oxidation and aerosol uptake

Abstract. Gaseous amines have attracted increasing attention due to their potential role in enhancing particle nucleation and growth and affecting secondary organic aerosol formation. Here we study with a chemistry transport model the global distributions of the most common and abundant amines in the air: monomethylamine (MMA), dimethylamine (DMA), and trimethylamine (TMA). We show that gas phase oxidation and aerosol uptakes are dominant sinks for these methylamines. The oxidation alone (i.e., no aerosol uptake) leads to methylamine lifetimes of 5–10 h in most parts of low and middle latitude regions. The uptake by secondary species with uptake coefficient (γ) of 0.03 (corresponding to the uptake by sulfuric acid particles) reduces the lifetime by ~30% over oceans and much more over the major continents, resulting in a methylamine lifetime of less than 1–2 h over central Europe, eastern Asia, and eastern US. With the estimated global emission flux, from the literature, our simulations indicate that [DMA] in the model surface layer over major continents is generally in the range of 0.1–2 ppt (parts per trillion) when γ = 0.03 and 0.2–10 ppt when γ = 0, and decreases quickly with altitude. [DMA] over oceans is below 0.05 ppt and over polar regions it is below 0.01 ppt. The simulated [MMA] is about a factor of ~2.5 higher while [TMA] is a factor of ~8 higher than [DMA]. The modeled concentrations of methylamines are substantially lower than the limited observed values available, with normalized mean bias ranging from −57 (γ = 0) to −88% (γ = 0.03) for MMA and TMA, and from −78 (γ = 0) to −93% (γ = 0.03) for DMA.

Structure of a methylamine sorption complex of fully dehydrated Cd 2+-exchanged zeolite X, ∣Cd 46(CH 3NH 2) 16∣[Si 100Al 92O 384]-FAU

The structure of a methylamine sorption complex of fully dehydrated, fully Cd 2+-exchanged zeolite X, ∣Cd 46(CH 3NH 2) 16∣[Si 100Al 92O 384]-FAU ( a = 24.863(4) Å), has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd 3 ¯ at 21(1) °C. An aqueous exchange solution 0.05 M in Cd 2+ was allowed to flow past the crystal for 5 days. The crystal was then dehydrated at 480 °C and 2 × 10 −6 Torr for 2 days (colorless), and exposed to 160 Torr of methylamine gas at 21(1) °C for 2 h (yellow). Diffraction data were then gathered in this atmosphere and were refined using all data to the final error indices (based upon the 524 reflections for which F o > 4 σ( F o)) of R 1 = 0.069 and wR 2 = 0.200. In this structure, Cd 2+ ions occupy three crystallographic sites. The octahedral sites I at the centers of the hexagonal prisms are filled with 16 Cd 2+ ions per unit cell (Cd–O = 2.369(8) Å). The remaining 30 Cd 2+ ions are located at two non-equivalent sites II with occupancies of 14 and 16. The 16 methylamine molecules per unit cell lie in the supercage where each interacts with one of the latter 16 site-II Cd 2+ ions: N–Cd = 2.11(8) Å. The imprecisely determined N–C bond length, 1.49(22) Å, agrees with that in gaseous methylamine, 1.474 Å. The positions of the hydrogen atoms were calculated. It appears that one of the amino hydrogen atoms hydrogen bonds to a 6-ring oxygen, and that the other forms a bifurcated hydrogen bond to this and another 6-ring oxygen. The methyl group is not involved in hydrogen bonding.

Nanostructures or submicrostructures from gas/solid reactions as probed by atomic force microscopy

Uniform nanostructures are formed by chemical reaction of gases with the surface regions of crystals. Their size and shape are determined and depicted by atomic force microscopy (AFM). Both depend on the crystal face and this proves that the bulk crystal structure is governing the long-range molecular transports in the range of up to 200 nm. Craters and volcanoes (eggs’ pallets), volcanoes, or valleys and heights are formed without intervening liquid phases upon reaction of a-cinnamic acid 1 and trans-stilbene 3 with gaseous bromine or (benzyl-) thiohydantoin 5 with gaseous methylamine. If chlorine is reacted briefly with a-cinnamic acid a nanoliquid is formed on the surface and this leads to nanostructuring with the AFM tip at low force via transport of liquid and recrystallization effects. Thus holes with flat bottoms are generated which increase steadily upon continuous AFM scanning. In the case of stilbene and bromine, the initial nanostructures undergo a thermal phase transformation which produces uniform flattened plugs of 250 nm height. The chemical generation of nanostructures is very efficient.

Vibrational excitation of methylamine by electron impact in the 4.5–30 eV energy range

Vibrational excitation of gaseous methylamine induced by 4.5–30 eV energy electrons has been investigated by the electron energy loss spectroscopy. The ratios of the differential cross sections for excitation of the vibrational modes and for elastic scattering measured as a function of the electron kinetic energies show that at 15 and 30 eV, the vibrational excitation occurs mainly through a direct mechanism. The absolute vibrationally elastic and inelastic differential cross sections have been measured at these impact energies. The cross sections for the inelastic scattering are strongly dependent on the vibrational mode which is excited.

Methylamines in the marine atmosphere

There is growing recognition of the possible importance of organic nitrogen compounds in the global atmospheric nitrogen cycle. Concentrations of gaseous methylamines (MAs) have been measured for the first time in the atmosphere of two non urban regions‐coastal Hawaii and Rhode Island. In Hawaii gaseous MA concentrations were as follows: monomethylamine (MMA), 11±5 pmol/m³ dimethylamine (DMA), 93±51 pmol/m³ and trimethylamine (TMA), 30±19 pmol/m³. Concentrations of these compounds were also measured in coastal seawater in Hawaii and Massachusetts and in rainwater from Rhode Island. Calculations of the fluxes of MAs across the air‐sea interface indicate that the oceans are a source for MMA and TMA but may be a sink for dimethylamine (DMA). The concentrations of MAs observed in rain can largely be explained by scavenging of gaseous MAs. Another important removal process for atmospheric MAs appears to be oxidation by OH radicals. Wet and dry removal combined with OH oxidation appear to balance oceanic production of MMA and TMA in the Hawaii region. Significant uncertainties remain about the cycling of DMA.

Silicon–nitrogen compounds. Part VIII. Base-promoted disproportionation of N-methyl- and N-phenyl-disilazane

Liquid N-methyldisilazane, (SiH3)2NMe, disproportionates when mixed with ammonia or methylamine at or below room temperature to give silane, hydrogen, and chiefly involatile products. Moderate heating is necessary with pyridine, trimethylamine, or tetradrofuran. Rates of silane evolution lie in the order: NH3 > NH2Me C5H5N NMe3 > C4H8O. N-Phenyldisilazane reacts similarly, but more slowly, and the order of bases is: NH3 > NH2Me PhNH2∼ C5H5N. From the stoicheiometry of the reactions and the properties, including i.r. spectra, of the products, it appears that tertiary amines yield essentially linear oligomers with SiH3NR end-groups. Primary amines and ammonia induce amine exchange and form cross-linked polmers with NR bridging groups and chiefly NHR end-groups. A mechanism to account for these facts is proposed. Polymer derived from (SiH3)2NMe and methylamine slowly reduces gaseous methylamine to ammonia at room temperature.

Ion–molecule reactions in gaseous methyl amine

The ion–molecule reactions in gaseous methyl amine have been studied. The following reactions have been identified and their rate coefficients (all in cm3 molecule−1 s−1 units) determined for ions of 3.4 eV ion exit energy. [Formula: see text]Reactions [a] and [c] were also studied at thermal ion energies and little variation of the rate coefficients with ion energy was found in contrast with theoretical predictions.

Comparison of T‐recoil and Wilzbach labeling of methylamine (preparation of methylamine‐CH2T)

AbstractRecoil labeling of methylamine via the 6Li(n,α) T‐reaction, using solutions of LiBr in liquid anhydrous methylamine, leads to a 10% radiochemical yield of methylamine‐CH2T. The yield is independent of the accompanying radiation dose within a wide range, thus allowing high‐dose pile irradiation. Specific activities up to 100 μC/mM can easily be obtained. For comparison Wilzbach labeling of gaseous methylamine has also been studied. Here, in contrast, poor tritium incorporation is observed, the L‐value for methylamine‐CH2T being 2.3 × 10−2.

The Radiolysis of Aqueous Methylammonium Ion

Methylamine Gaseous methylamine (Matheson, 98 % minimum) was used as received. This gas contains small amounts of dimethylamine (0.4 % maximum) and of trimethylamine (0.8 % maximum). Stock solutions of the perchlorate and sulfate were obtained by bubbling the gas into triply distilled water containing appropriate amounts of reagent perchloric acid (Baker and Adamson 70 %) or sulfuric acid (reagent grade) until the pH was about 7. To avoid contamination of these solutions by chloride ions from the calomel electrode, small samples were withdrawn for pH measure1

The thermal oxidation of methylamine

A study has been made of the kinetics of the reaction of gaseous methylamine with oxygen. Since the nitrogen atom is eliminated from the molecule in the course of the oxidation, analysis of the products formed at various stages yields evidence about the reaction mechanism which is not available in the study of hydrocarbons. The variation of oxidation rate with time may be represented by the equation dp / dt ═ B e ct + D , and the influence of reactant pressures and of temperature on C and D has been determined. Inert gases do not affect the course of the oxidation, but an increase in surface inhibits the reaction to an extent dependent on the composition of the reactant mixture. Since the later stages of the oxidation are complicated by secondary reactions, the analytical results for the early stages provide the most useful information about the main chemical reactions occurring. The greater part of the combined nitrogen is initially converted to ammonia, but small quantities of nitrogen oxides are also formed. The fact that the concentration of ammonia is lowered and that of nitrogen oxides is raised by increasing oxygen pressure suggests that both products arise from reaction of NH 2 radicals with the original reactants. One source of these radicals is probably the breakdown of intermediate peroxides such as NH 2 CH 2 —O—O—H, the concentration of which largely controls the rate of reaction. Such a decomposition should give rise to formaldehyde and ammonia in approximately equal amounts. The non-equivalence of these products suggests, however, that the major part of the ammonia is formed in some other way, and it is supposed that peroxide radicals such as NH 2 CH 2 —O—O— may, instead of reacting with methylamine to give the peroxide as usually postulated, themselves decompose unimolecularly to give ammonia and carbon monoxide. An attempt is made to construct a simplified theory of the oxidation, to estimate the relative frequencies of some of the proposed reaction stages and hence to calculate certain ratios of velocity constants. The suggested mechanism leads to kinetic relationships in close agreement with those found experimentally.

The Pressure-Volume Relations of the Gaseous Methylamines at 0° and Reduced Pressures

The Pressure-Volume Relations of the Gaseous Methylamines at 0° and Reduced Pressures

The Absorption Spectra of Gaseous Methylamine and Dimethylamine in the Photographic Infra-Red

The absorption spectra of gaseous methylamine and dimethylamine have been measured in the region from 6000 to 12,000A using a 105-foot stainless steel absorption tube and a 3-m grating spectrograph. Absorption bands were observed at 7940, 9100, 9940, 10,070, 10,330 and 11,800A in methylamine and at 7940, 8045, 9100, 10,360, 10,625 and 11,800A in dimethylamine. The only band showing resolvable fine structure was that at 9940A in methylamine. Wherever possible the observed bands have been assigned to overtones and combinations of the fundamental N–H and C–H valence vibrations.