Ethylene Molecules Research Articles

Regulating interfacial structure enables high-voltage dilute ether electrolytes

Poor oxidation stability of ether solvents at the cathode restricts the use of dilute ether electrolytes with conventional concentrations around 1 M in high-voltage, lithium-metal batteries. Here, we report an anion-adsorption approach to altering the ether solvent environment within the electrical double layer (EDL) at the cathode by adding a small amount of nitrate so that the oxidation tolerance of nitrate-containing dilute ether electrolytes is enhanced up to 4.4 V (versus Li/Li + ), leading to complete compatibility with high-voltage cathodes and exhibiting superior cycling stability. Constant potential molecular dynamics simulations reveal that ether molecules are mostly excluded from the cathode because of nitrate occupation in the inner layer of the EDL, thus suppressing ether oxidative decomposition. This work highlights that regulating the interfacial structure by adding surface adsorbates, rather than passivating the cathode-electrolyte interphase or changing ion solvation, can help to enhance the oxidation stability of ether solvents. • A high-voltage dilute ether electrolyte (at 1 M salt concentration) is developed • Molecular mechanism that surface adsorbates suppress solvent decomposition is revealed • A series of adsorption-type additives for high-voltage dilute ethers are proposed Wang et al. propose a simple and convenient approach to enhance the oxidation stability of dilute ether electrolytes (at 1 M salt concentration), by adding a small amount of nitrate (50 mM). This approach addresses a long-standing voltage limitation for dilute ether electrolytes.

Infrared spectroscopy of ions and ionic clusters upon ionization of ethane in helium droplets.

Helium droplets are unique hosts for isolating diverse molecular ions for infrared spectroscopic experiments. Recently, it was found that electron impact ionization of ethylene clusters embedded in helium droplets produces diverse carbocations containing three and four carbon atoms, indicating effective ion-molecule reactions. In this work, similar experiments are reported but with the saturated hydrocarbon precursor of ethane. In distinction to ethylene, no characteristic bands of larger covalently bound carbocations were found, indicating inefficient ion-molecule reactions. Instead, the ionization in helium droplets leads to formation of weaker bound dimers, such as (C2H6)(C2H4)+, (C2H6)(C2H5)+, and (C2H6)(C2H6)+, as well as larger clusters containing several ethane molecules attached to C2H4 +, C2H5 +, and C2H6 + ionic cores. The spectra of larger clusters resemble those for neutral, neat ethane clusters. This work shows the utility of the helium droplets to study small ionic clusters at ultra-low temperatures.

Structural changes due to the ordered guest molecules in deuterated ethane hydrate

Ethane hydrate, a natural gas hydrate, has been considered to only have a cubic symmetry known as structure I. Neutron diffraction measurement of deuterated ethane hydrate was performed from 10 K to 150 K. The diffraction patterns of deuterated ethane hydrate drastically changed below 30 K. A new hexagonal crystal structure with ordered ethane molecules was found as a clathrate hydrate structure. This phase transition was concerned with the thermal motion of the ethane molecules.

Graphene modified “black {0 0 1}TiO2” nanosheets for photocatalytic oxidation of ethylene: The implications of chemical surface characteristics in the reaction mechanism

In this work, crystal facets, bandgap, size and shape of reduced graphene oxide (rGO) modified anatase {001} black TiO2 nanosheets (rGO-B-TiO2 NSTs) were tailored for the photocatalytic oxidation of ethylene under high humidity content. XRD, Raman and HR-TEM analyses confirm that rGO-B-TiO2 NSTs have a 94 % of exposed {001} facets with high number of oxygen vacancies. In addition, rGO-B-TiO2 NSTs exhibit increased values of surface area and porosity compared to its pristine form. A 48 and 34 μmol g−1 of ethylene are adsorbed at the surface of rGO-B-TiO2 NSTs in the absence and in the presence of humidity, respectively. In addition, operando DRIFTS analyses provide the insight of surface interactions between ethylene molecules and adsorption sites of rGO-B-TiO2 NSTs. The photocatalytic removal efficiencies of the synthesized materials under both UV and visible light irradiation proceed as follows: rGO-B-TiO2 NSTs > B-TiO2 NSTs > TiO2 NSTs > commercial TiO2 NPs. Further, ethylene is very quickly photocatalytic oxidized when rGO-B-TiO2 NSTs is applied under UV light irradiation, having a 72 and 92 % ethylene removal in the absence and in the presence of humidity, respectively. Moreover, a 48 and 58 % of ethylene removal takes place in the absence and presence of humidity under visible light irradiation, respectively. Results indicate that rGO-B-TiO2 NSTs boost the photocatalytic activity through their virtue of visible-light absorption properties (Bandgap = 2.61 eV) and the rapid electron-hole separation at the rGO {001} black TiO2 NSTs interfaces. Such findings are confirmed through UV-visible diffused reflectance, photoelectrochemical and photoluminescence analyses. Nanosheets made of rGO modified {001} black TiO2 could be used as an effective photocatalyst for the removal of ethylene from large volume fruit storage areas by exploiting a simple light source in the presence of high content of humidity.

Role of the Hydroxyl Groups Coordinated toTiO2 Surface on the Photocatalytic Decomposition of Ethylene at Different Ambient Conditions

The titania pulp—a semi product received from the industrial production of titania white—was submitted for the thermal heating at 400–600 °C under Ar and H2 to obtain TiO2 with different structure and oxygen surface defects. Heating of titania in H2 atmosphere accelerated dehydration and crystallisation of TiO2 compared to heating in Ar. TiO2 prepared at 500 and 600 °C under H2 had some oxygen vacancies and Ti3+ centres (electron traps), whereas TiO2 obtained at 450 °C under H2 exhibited some hole traps centres. The presence of oxygen vacancies induced adsorption of atmospheric CO2. It was evidenced, that ethylene reacted with TiO2 after UV irradiation. Formic acid was identified on TiO2 surface as the reaction product of ethylene oxidation. Hydroxyl radicals were involved in complete mineralisation of ethylene. TiO2 prepared at 500 °C under H2 was poorly active because some active sites for coordination of ethylene molecules were occupied by CO2. The most active samples were TiO2 with high quantity of OH terminal groups. At 50 °C, the physically adsorbed water molecules on titania surface were desorbed, and then photocatalytic decomposition of ethylene was more efficient. TiO2 with high quantity of chemisorbed OH groups was very active for ethylene decomposition. The acidic surface of TiO2 enhances its hydroxylation. Therefore, it is stated that TiO2 having acidic active sites can be an excellent photocatalyst for ethylene decomposition under UV light.

Cobalt/Lewis acid cooperative catalysis for reductive etherification of ketones and aldehydes with alcohols

Ether synthesis is a ubiquitous transformation in both research and industrial settings. In this respect, reductive etherification of carbonyl compounds with alcohols using H 2 as the reductant represents an ideal approach due to the ready availability of reactants, high atom economy, and potential for product diversity. Nevertheless, in contrast to the well-established reductive amination, the development of reductive etherification has fallen far behind, limited by more side reaction pathways. Herein we report a novel cooperative cobalt/Lewis acid (LA)-catalyzed reductive etherification of ketones and aldehydes with alcohols using H 2 as the reductant. The LA co-catalyst is crucial for the effective control of chemoselectivity by facilitating the formation and hydrogenolysis of (hemi)ketal intermediates. In addition, the direct hydrogenation products of ketone can be further converted to ether products via LA-catalyzed etherification with alcohol substrates. The utility and scope were demonstrated by an efficient synthesis of multifarious ether molecules, including pharmaceuticals and nature product derivatives. • Cobalt/Lewis acid cooperative catalysis for reductive etherification • A slight excess of alcohols • Excellent functional group tolerance and high selectivity • Detailed mechanistic investigations Ether synthesis is a ubiquitous transformation in both research and industrial settings. The Williamson ether synthesis is a long-established method for the synthesis of primary alkyl ethers via SN2 substitution. However, in contexts involving secondary or tertiary alkyl halides, the reaction often derails, leading to elimination byproducts or to no reaction at all. In this respect, reductive etherification of carbonyl compounds with alcohols using H 2 as the reductant represents an alternative ideal approach. Nevertheless, in contrast to the well-established reductive amination, the development of reductive etherification has fallen far behind, being restricted by more side reaction due to a slower formation of oxocarbenium intermediates. In this work, we disclosed a novel cooperative cobalt/Lewis acid (LA)-catalytic system, which enabled effective reductive etherification of ketones and aldehydes with alcohols using H 2 as the reductant. A cobalt/Lewis acid cooperative catalytic process for reductive etherification of ketones and aldehydes with alcohols was developed. The notable feature of this methodology is the ability to effectively control reaction selectivity, enabling different reaction pathways to form the same ether product rather than accessing to various possible side products.

Synthesis and Characterization of New Nanocomposites Based on Montmorillonite and Hexahydroquinolinyl Ether Hybrids

AbstractFamiliarly, montmorillonite (MMT) ‐ based composites are prepared by the absorption method, which produced unstable MMT composites, since the adsorbates were easily pull out from MMT. Herein, using a new technique, the hexahydro‐ quinolinylhexahydroquinolinyl ethers resulting from the cyclization reaction of 1,3‐cyclohexanedione with p‐aminophenol and arylidinemalono‐ nitrilesarylidinemalononitriles in presence of Ca‐montmorillonite (Ca‐MMT), were grafted on Ca‐MMT surface via formation of coordinate bonds to produce stable nanocomposites. In these reactions, Ca‐MMT played as a heterogeneous catalyst and as the hydrophobic surface chemically bonded with the formed ether molecules. NMR, FTIR and XRD analyses confirmed the successful surface modification of the nanoparticles clay with the formed ethers molecules via formation of coordinate and hydrogen bonds. These stable nanocomposites are characterized by their thermal stability and higher solubility in dioxane and dimethyl sulphoxide solvents.Also, these nanocomposites has a potential application in environment, biomedicine and engineered barriers.

The Structure and Location of 18-Crown-6 Ether in Zeolites RHO and ZK-5

The use of organic additives presents the greatest versatility and control of zeolite synthesis in order to prepare novel architectures for desired applications. Despite this prospect, there is little clarity of how organic additives are involved in framework assembly and the range of behaviours that are available. To address this issue, we have considered zeolites RHO and ZK-5 which can both be prepared using 18-crown-6 ether as an additive. Previously, this additive has shown to employ different structure directing behaviours to assemble a variety of zeolites. We have used high resolution powder X-ray diffraction and Rietveld refinement to determine structural models for zeolites RHO and ZK-5 with 18-crown-6 ether occluded in the framework. In doing so, we can observe the identity, location and orientation of the occluded additive and reason the structure directing behaviour in synthesis. We report that the isolated 18-crown-6 ether molecule is involved in the assembly of zeolite RHO, and for zeolite ZK-5 it is the K+ coordinated macrocation. In both cases the relevant additive is disordered in the framework, suggesting that they behave as space-filling species that stabilise the formation of the α-cage.

Elongation and branching of α-olefins by two ethylene molecules.

α-Olefins are important starting materials for the production of plastics, pharmaceuticals, and fine and bulk chemicals. However, the selective synthesis of α-olefins from ethylene, a highly abundant and inexpensive feedstock, is restricted, and thus a broadly applicable selective α-olefin synthesis using ethylene is highly desirable. Here, we report the catalytic reaction of an α-olefin with two ethylene molecules. The first ethylene molecule forms a 4-ethyl branch and the second a new terminal carbon-carbon double bond (C2 elongation). The key to this reaction is the development of a highly active and stable molecular titanium catalyst that undergoes extremely fast β-hydride elimination and transfer.

Catalyst coaxed to make branched α-olefins.

Process conditions allow a titanium catalyst to add just two ethylene molecules to an α-olefin.

Adiponitrile (ADN): A Stabilizer for the LiNi0.8Co0.1Mn0.1O2 (NCM811) Electrode/Electrolyte Interface of a Graphite/NCM811 Li-Ion Cell

Adiponitrile (ADN) is studied as an additive of commercial carbonate electrolyte for a graphite/NCM811 Li-ion cell in this work. Compared with the cell using a baseline electrolyte, the cycling stability of the cells using 0.2, 0.5, 1, and 2 wt % ADN-added electrolytes is significantly improved. Among them, the effect is most prominent when the ADN content is 0.5 wt %, and the capacity retention rate of the cell after 200 cycles at 0.3 C is increased by 17.6%. Scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy analyses confirm that ADN can make the coating layer formed on the cathode and anode surfaces of the cell denser and uniform. The formation of the cathodic coating layer does not obey the usual mechanism of adsorption between the nitrile group and metal ions, but it may be due to the polymerization of ADN initiated by carbocations from the oxidation of solvent molecules (ethylene carbonate/ethyl methyl carbonate) in the electrolyte. The cathodic coating layer greatly decreases the oxidation of the electrolyte so that a stable coating layer (also called solid electrolyte interface/SEI) can be formed on the anode, which is the reason for improvement of the cycling performance of the cell. However, the formation of the anode SEI layer is almost independent of ADN, and it still depends on the common reduction reaction of the electrolyte.

The effect of alkylation on the micro-solvation of ethers revealed by highly localized water librational motion.

The specific far-infrared spectral signatures associated with highly localized large-amplitude out-of-plane librational motion of water molecules have recently been demonstrated to provide sensitive spectroscopic probes for the micro-solvation of organic molecules [Mihrin et al., Phys. Chem. Chem. Phys. 21(4), 1717 (2019)]. The present work employs this direct far-infrared spectroscopic approach to investigate the non-covalent intermolecular forces involved in the micro-solvation of a selection of seven ether molecules with systematically varied alkyl substituents: dimethyl ether, diethyl ether, diisopropyl ether, ethyl methyl ether, t-butyl methyl ether, and t-butyl ethyl ether. The ranking of the observed out-of-plane water librational band signatures for this selected series of ether-water complexes embedded in inert neon matrices at 4K reveals information about the interplay of directional intermolecular hydrogen bond motifs and non-directional and long-range dispersion interactions for the micro-solvated structures. These far-infrared observables differentiate minor subtle effects introduced by specific alkyl substituents and serve as rigorous experimental benchmarks for modern quantum chemical methodologies of various levels of scalability, which often fail to accurately predict the structural variations and corresponding vibrational signatures of the closely related systems. The accurate interaction energies of the series of ether-water complexes have been predicted by the domain based local pair natural orbital coupled cluster theory with single-, double-, and perturbative triple excitations, followed by a local energy decomposition analysis of the energy components. In some cases, the secondary dispersion forces are in direct competition with the primary intermolecular hydrogen bonds as witnessed by the specific out-of-plane librational signatures.

Heteroleptic carbazolato-barium hydroborates and a related separated ion pair

The syntheses and characterisation of two molecular barium-hydroborate complexes supported by a bulky bis(imino)carbazolate ligand, namely [{CarbDipp}Ba(μ-H2Bpin)]3 (23) and [{CarbDipp}Ba(H2-9BBN).Et2O] (3.Et2O), are presented. These two complexes are obtained in high yields upon reaction of the amido precursor [{CarbDipp}BaN(SiMe3)2] (1) with the commercially available pinacolborane or [H-9BBN]2, respectively. The solid-state molecular structures of the complexes were solved, and show 23 to form a solvent-free cyclic trimer, whereas the monomeric 3.Et2O is solvated by one molecule of diethyl ether. Furthermore, the well-defined ion pair [{CarbDipp}Ba.(Et2O)2]+[H2N{B(C6F5)3}2]– (4), a rare occurrence of soluble barium cation, was also obtained in good yield upon treatment of 1 with Bochmann’s acid. Its X-ray structure was solved and reveals the absence of interaction between the metal cation and its counter-ion. Finally, the structure of the seven-coordinated, dicationic [Ba.(thf)7]2+[H2N{B(C6F5)3}2]–2 (5) is also presented.

Carbon K-edge x-ray emission spectroscopy of gas phase ethylenic molecules

We report on the C K-edge x-ray absorption spectra and the resonant (RXES) and non-resonant (NXES) x-ray emission spectra of ethylene, allene and butadiene in the gas phase. The RXES and NXES show clear differences for the different molecules. Overall both types of spectra are more structured for ethylene and allene, than for butadiene. Using density functional theory–restricted open shell configuration interaction single calculations, we simulate the spectra with remarkable agreement with the experiment. We identify the spectral features as being due to transitions involving localised 1s orbitals. For allene, there are distinct spectral bands that reflect transitions predominantly from either the central or terminal carbon atoms. These results are discussed in the context of ultrafast x-ray studies aimed at detecting the passage through conical intersections in polyatomic molecules.

Halides and the carbon-carbon double bond: Interactions of ethylene with bromide and iodide

A combined experimental and theoretical approach has been used to study the bromide-ethylene and iodide-ethylene gas-phase complexes. Experimental anion photoelectron spectra show the electron stabilisation of the complexes to be 0.19 eV and 0.14 eV associated with the bromide and iodide complexes respectively. High-level CCSD(T) calculations predict two minima with respect to each halide; the halide either appends linearly to a single hydrogen of the ethylene molecule or appends orthogonally to the carbon–carbon double bond. The two structural motifs are found to be close in energy, with the difference in dissociation energy associated with both halides determined to be approximately 1.3 kJ mol−1.

Overcoming structural collapse in stable zirconium phosphonate materials for strontium removal

Zirconium phosphate materials are promising adsorbents for removing metal ions from harsh conditions such as nuclear wastewater. However, the layered structure of zirconium phosphate distorts or even collapses under strong acidic conditions, lowering the industrial efficiency of zirconium phosphate in spent fuel reprocessing. We address this problem and show two different methods for improving acid tolerance of zirconium phosphate materials by intercalating aza-18 crown 6 ethers. These zirconium materials retain their layer-structure by guest crown ether molecules supporting the planes of host α-ZrP, and exhibit excellent stability in acidic conditions. In particular, D-DZ-ZrP possesses excellent stability even in 3 mol L-1 HNO3, HCl and H2SO4 solutions, due to the diaza-18 crown 6 ether can support the bilateral planes simultaneously by forming the stronger P-C covalent bond. More importantly, the existence of aza-18 crown 6 ethers in interlayer spacing, which produce the wide layer distances and abundant adsorption sites, make these samples exhibit the strong ability for selectively capturing of Sr2+ from mixed solutions. Remarkably, D-AZ-ZrP and D-DZ-ZrP especially showed the excellent adsorption properties in highly concentrated HNO3 solutions because of their excellent stability. In addition, the substitution of –NH groups in the crown ether ring favors the coordination interaction with Sr2+, which is confirmed by DFT calculations. Sr2+ adsorption capacities onto D-DZ-ZrP reached 88.34 mg g−1, which is also 2.5 times than that on the traditional α-ZrP. Our work poses a new way to overcome the structure collapse of the layered materials, and improve their applicability for use in actual industrial process.

Host-Guest Chemistry for Simultaneous Imaging of Endogenous Alkali Metals and Metabolites with Mass Spectrometry.

Sodium and potassium are biological alkali metal ions that are essential for the physiological processes of cells and organisms. In combination with small-molecule metabolite information, disturbances in sodium and potassium tissue distributions can provide a further understanding of the biological processes in diseases. However, methods using mass spectrometry are generally tailored toward either elemental or molecular detection, which limits simultaneous quantitative mass spectrometry imaging of alkali metal ions and molecular ions. Here, we provide a new method by including crown ether molecules in the solvent for nanospray desorption electrospray ionization mass spectrometry imaging (nano-DESI MSI) that combines host–guest chemistry targeting sodium and potassium ions and quantitative imaging of endogenous lipids and metabolites. After evaluation and optimization, the method was applied to an ischemic stroke model, which has highly dynamic tissue sodium and potassium concentrations, and we report 2 times relative increase in the detected sodium concentration in the ischemic region compared to healthy tissue. Further, in the same experiment, we showed the accumulation and depletion of lipids, neurotransmitters, and amino acids using relative quantitation with internal standards spiked in the nano-DESI solvent. Overall, we demonstrate a new method that with a simple modification in liquid extraction MSI techniques using host–guest chemistry provides the added dimension of alkali metal ion imaging to provide unique insights into biological processes.

Phytohormones Trigger Drought Tolerance in Crop Plants: Outlook and Future Perspectives.

In the past and present, human activities have been involved in triggering global warming, causing drought stresses that affect animals and plants. Plants are more defenseless against drought stress; and therefore, plant development and productive output are decreased. To decrease the effect of drought stress on plants, it is crucial to establish a plant feedback mechanism of resistance to drought. The drought reflex mechanisms include the physical stature physiology and biochemical, cellular, and molecular-based processes. Briefly, improving the root system, leaf structure, osmotic-balance, comparative water contents and stomatal adjustment are considered as most prominent features against drought resistance in crop plants. In addition, the signal transduction pathway and reactive clearance of oxygen are crucial mechanisms for coping with drought stress via calcium and phytohormones such as abscisic acid, salicylic acid, jasmonic acid, auxin, gibberellin, ethylene, brassinosteroids and peptide molecules. Furthermore, microorganisms, such as fungal and bacterial organisms, play a vital role in increasing resistance against drought stress in plants. The number of characteristic loci, transgenic methods and the application of exogenous substances [nitric oxide, (C28H48O6) 24-epibrassinolide, proline, and glycine betaine] are also equally important for enhancing the drought resistance of plants. In a nutshell, the current review will mainly focus on the role of phytohormones and related mechanisms involved in drought tolerance in various crop plants.

Kinetic model of ethylene oxidation in the presence of both ethylene dichloride (1,2-dichloroethane) and carbon dioxide over a highly selective silver catalyst

Experiments were conducted to obtain the kinetic model of ethylene oxidation over a commercial highly selective catalyst αAl2O3/Ag-Cs-Re, for the first time. A gas mixture of 4.15–7.5% O2, 24.23% C2H4, 0–3.464% CO2, 0.56 ppm C2H4Cl2 and N2 at 17.4 bar and 208–240 °C was deployed, similar to that in industry. An adsorbed atomic oxygen and a gaseous ethylene molecule through modified or original Eley-Rideal mechanisms were responsible for both the partial and complete oxidation of ethylene. The partial oxidation engaged an additional uncovered active site in surface reaction compared to the complete oxidation. The surface reaction was the rate-limiting step under the experimental conditions. The proposed model is in remarkable agreement with the experimental data. The addition of CO2 to the feed was proved detrimental to the EO selectivity, only suppressing the EO production rate. Temperature raise was much in favor of the CO2 production rate, decreasing the EO selectivity.

Radiation-induced transformations of acetaldehyde molecules at cryogenic temperatures: a matrix isolation study.

Acetaldehyde is one of the key small organic molecules involved in astrochemical and atmospheric processes occurring under the action of ionizing and UV radiation. While the UV photochemistry of acetaldehyde is well studied, little is known about the mechanism of processes induced by high-energy radiation. This paper reports the first systematic study on the chemical transformations of CH3CHO molecules resulting from X-ray irradiation under the conditions of matrix isolation in different solid noble gases (Ne, Ar, Kr, and Xe) at 5 K. CO, CH4, H2CCO, H2CCO-H2, C2H2⋯H2O, CH2CHOH, CH3CO˙, CH3˙, HCCO˙, and CCO were identified as the main radiolysis products. The dominant pathway of acetaldehyde degradation involves C-C bond cleavage leading to the formation of carbon monoxide and methane. The second important channel is dehydrogenation resulting in the formation of ketene, a potentially highly reactive species. It was found that the matrix significantly affected both the decomposition efficiency and distribution of the reaction channels. Based on these observations, it was suggested that the formation of the methyl radical as well as vinyl alcohol and the C2H2⋯H2O complex presumably included a significant contribution of ionic pathways. The decomposition of acetyl radicals under photolysis with visible light leading to the CH3˙-CO radical-molecule pair was observed in all matrices, while the recovery of CH3CO˙ in the dark at 5 K was found only in Xe. This finding represents a prominent example of matrix-dependent chemical dynamics (probably, involving tunnelling), which deserves further theoretical studies. Probable mechanisms of acetaldehyde radiolysis and their implications for astrochemistry, atmospheric chemistry and low-temperature chemistry are discussed.