Ethylene Molecules Research Articles

Flat crown ethers with planar tetracoordinate carbon atoms

AbstractNovel flat crown ether molecules have been characterized in silico using density functional theory. Monomer units of Si2C3 with a planar tetracoordinate carbon (ptC) atom have been used as building blocks. Alkali (Li+, Na+, K+, Rb+, and Cs+) and alkaline‐earth (Be2+, Mg2+, Ca2+, Sr2+, and Ba2+) metal ions, and uranyl (UO) ion selective complexes have also been theoretically identified. The high symmetry and higher structural rigidity of the host molecules may likely impart higher selectivity in chelation. The potential energy surface of the parent elemental composition, Si2C3H2, has been investigated using coupled‐cluster (CC) approximation. The molecule with a ptC atom within the latter is a low‐lying isomer lying 12.41 kcal mol−1 above the global minimum at the CCSD(T)/cc‐pVTZ level. The crown ether molecules identified here could theoretically be considered the derivatives of the ptC atom isomer. Theoretical binding energies (ΔE; 0 K) and thermally corrected Gibbs free energies (ΔG; 298.15 K) for crown ether molecules have been computed to gauge their binding affinities.

Dimethyl and ethyl methyl ether adsorption studies on β-antimonene nanosheets – a first-principles study

ABSTRACT Dimethyl ether (DME) and ethyl methyl ether (EME) are highly toxic volatile organic compounds (VOCs) that find their potential importance in many industries. Besides, DME and EME are highly flammable VOCs, which may cause a fire hazard. Also, both DME and EME are toxic to humans and animals. Thus, the detection of ether molecules in the atmosphere is important using chemical sensors. The novel β-antimonene nanosheet (β-SbNS) is taken as a base substrate to study the interaction behaviour of DME and EME molecules on the surface using density functional theory (DFT) method. Moreover, β-SbNS possesses semiconductor nature with an energy gap of 1.293 eV. At first, the structural stability of β-SbNS was confirmed with the negative magnitude of cohesive formation energy. In addition, the electronic characteristics of β-SbNS are studied in terms of the projected-density of states and band maps. Importantly, different global minima sites (bridge, ring, and top) of DME and EME vapour on β-SbNS were explored with the influence of significant factors, namely adsorption energy, average band gap changes, and Bader charge transfer. The findings of the proposed work advocate that β-SbNS can be competently used as a chemi-resistive sensor to detect DME and EME vapour molecules.

Epoxidation of Cardanol's Terminal Double Bond.

In this investigation, the terminal double bonds of the side chain epoxidized cardanol glycidyl ether (SCECGE) molecule were further epoxidized in the presence of Oxone® (potassium peroxomonosulfate) and fluorinated acetone. Regular methods for the double bond epoxidation are not effective on the terminal double bonds because of their reduced electronegativity with respect to internal double bonds. The terminal double bond functionality of the SCECGE was epoxidized to nearly 70%, increasing the epoxy functionality of SCECGE from 2.45 to 2.65 epoxies/molecule as measured using proton magnetic nuclear resonance (1H-NMR). This modified material—side chain epoxidized cardanol glycidyl ether with terminal epoxies (TE-SCECGE)—was thermally cured with cycloaliphatic curing agent 4-4′-methylenebis(cyclohexanamine) (PACM) at stoichiometry, and the cured polymer properties, such as glass transition temperature (Tg) and tensile modulus, were compared with SCECGE resin cured with PACM. The Tg of the material was increased from 52 to 69 °C as obtained via a dynamic mechanical analysis (DMA) while the tensile modulus of the material increased from 0.88 to 1.24 GPa as a result of terminal double bond epoxidation. In addition to highlighting the effects of dangling side groups in an epoxy network, this modest increase in Tg and modulus could be sufficient to significantly expand the potential uses of amine-cured cardanol-based epoxies for fiber reinforced composite applications.

Volumetric Behaviour of Binary Mixtures of Diethyl Ether + (C1 – C4) Alkoxyethanols at Different Temperatures

Densities of pure liquids and binary mixtures of diethyl ether (DEE) with 2-alkoxyethanols (2- methoxyethanol, 2-ethoxyethanol and 2-butoxyethanol) have been determined over the entire range of solvent compositions at (293.15, 298.15 and 303.15) K. Excess molar volumes (VM E ) have been calculated from the density data and were fitted into the Redlich-Kister type polynomial equation to obtain the fitting parameters Ai. The values of excess molar volumes, vm E were negative in regions of low diethyl ether (DEE) composition and small positive values were observed in regions of high diethyl ether (DEE) compositions in all the systems studied. VM E values were also found to decrease with increase in temperature and increase in chain length of the 2-alkoxyethanols. The above trends were attributed to the combined effects of disruption and formation of hydrogen bonds between like molecules of 2- alkoxyethanols and unlike molecules of diethyl ether (DEE), respectively.

Micro-solvation and counter ion effects on ionic reactions: Activation of potassium fluoride with 18-crown-6 and tert-butanol in aprotic solvents

Ionic reactions have an important solvent effect and the first solvation shell makes the most important contribution for determining the reactivity. In the case of nucleophilic fluorination with potassium fluoride, the solubilization of the salt is another aspect which needs be considered. In the present work, the effect of adding stoichiometric quantity of 18-crown-6 and the bulky alcohol tert-butanol to the reaction of potassium fluoride with alkyl bromide in toluene and acetonitrile solvents was investigated by theoretical methods as molecular dynamics and electronic structure calculations, as well as by experiments. The calculations indicate that the fluoride ion in the KF (18-crown-6) complex interacts with tert-butanol molecules forming aggregates with one (acetonitrile solvent) and three (toluene solvent) tert-butanol molecules. The calculations predict that formation of these aggregates increase the solubilization of KF and produces and important rate acceleration effect in both acetonitrile and toluene solvents, which is experimentally observed. In the concentration around 0.75 mol L−1 of the tert-butanol, the reaction rate is proportional to the alcohol concentration and the rate of alkyl halide decay becomes 10 times higher than the rate without this alcohol. The present results point out that both the interactions of KF with crown ether and tert-butanol molecules have a synergic effect, increasing its reactivity towards SN2 reactions.

Raman spectroscopy of ethane (C2H6) to 120 GPa at 300 K

AbstractWe have conducted a Raman study of solid ethane (C2H6) at pressures up to 120 GPa at 300 K. We observe changes within the ν3 and ν11 Raman‐active vibrational modes providing evidence for several previously unobserved phase transitions at room temperature. These are located from 16 to 20 GPa, ~35 GPa, and ~60 GPa. We also could no longer measure the ν3 and ν11 modes from 75 GPa onward. We did not, however, observe any signs of the ethane molecule undergoing decomposition, up to the highest pressures measured. We also recorded spectra of the (2ν8, 2ν11), ν1, and ν10 modes but observed more limited changes in the behaviour of these modes.

Understanding real-time time-dependent density-functional theory simulations of ultrafast laser-induced dynamics in organic molecules.

Real-time time-dependent density functional theory, in conjunction with the Ehrenfest molecular dynamics scheme, is becoming a popular methodology to investigate ultrafast phenomena on the nanoscale. Thanks to recent developments, it is also possible to explicitly include in the simulations a time-dependent laser pulse, thereby accessing the transient excitation regime. However, the complexity entailed in these calculations calls for in-depth analysis of the accessible and yet approximate (either "dressed" or "bare") quantities in order to evaluate their ability to provide us with a realistic picture of the simulated processes. In this work, we analyze the ultrafast dynamics of three small molecules (ethylene, benzene, and thiophene) excited by a resonant laser pulse in the framework of the adiabatic local-density approximation. The electronic response to the laser perturbation in terms of induced dipole moment and excited-state population is compared to the results given by an exactly solvable two-level model. In this way, we can interpret the charge-carrier dynamics in terms of simple estimators, such as the number of excited electrons. From the computed transient absorption spectra, we unravel the appearance of nonlinear effects such as excited-state absorption and vibronic coupling. In this way, we observe that the laser excitation affects the vibrational spectrum by enhancing the anharmonicities therein, while the coherent vibrational motion contributes to stabilizing the electronic excitation already within a few tens of femtoseconds.

Toxic volatile organic compounds sensing by Al2C monolayer: A first-principles outlook

Adsorption and detection performance of two-dimensional Al2C monolayer for four toxic volatile organic compounds (VOCs) viz. acetaldehyde, ethylene oxide, vinyl chloride, and benzene are investigated using first-principles calculations based on the periodic density functional theory. The band gap of Al2C nanosheet is changed substantially from 0.9 eV to 0.52, 1.41, 1.57, and 0.42 eV upon interaction with acetaldehyde, ethylene oxide, vinyl chloride, and benzene molecules respectively. The Al2C nanosheet maintains its semiconductor properties even after the adsorption of the four VOCs. The adsorption energy of four typical toxic volatile organic compounds (VOCs) viz. acetaldehyde, ethylene oxide, vinyl chloride, and benzene on the Al2C monolayer is in a range of -1.972 eV to -2.244 eV, which is higher than the adsorption energies obtained for several other VOCs adsorbed on different materials. Larger VOCs adsorption energies on Al2C monolayer obtained here may lead to adsorption of more VOC molecules on the material and consequently enhanced sensitivity. The results of ab initio molecular dynamics (AIMD) calculations for the studied complexes confirm their stability under the considered conditions of the simulation. Pristine Al2C monolayer might be a superior adsorbent and a promising sensing medium for toxic VOCs in real applications.

Molecular dynamic investigations of aluminum nanoparticles coated by the mixtures of ethanol and diethyl ether with different molecular proportions

Aluminum nanoparticles (ANPs) are considered energetic, economical, and eco-friendly additives. In this investigation, advanced ReaxFF molecular dynamics (MD) simulation has been used to discover the mechanism of coating ether and ethanol molecules on ANPs. Those MD results generally reveal the dynamics process of ethanol and ether adsorption. It is found that the adsorption of ethanol and ether molecules is not a physical adsorption process only. Newly generated aluminum-oxygen bonds are formed between oxygen atoms and aluminum atoms. Those oxygen atoms come from both ethanol and ether molecules. Moreover, ethanol and ether molecules generate ethyl and new ethanol molecules during the adsorption process. The radial distribution function curves and adsorption curves are used to describe the adsorption process. The results show that the adsorption amount of ethanol molecule is significantly higher than that of the ether molecule. It is observed that the outermost aluminum atoms form an organic-provided alumina layer, the inside of ANPs is active aluminum atoms, and the outside is the organic coating layer. Heating could eliminate the hydrogen-bonding between solution molecules. High pressure and high temperature destroy the external structure of aluminum particles, which makes atoms migrate to the interior of aluminum particles. Finally, the oxidation resistance test shows that at 300 K, the organic coating layer can maintain good stability and oxidation resistance.

Compressing Double [7]Helicene by Successive Charging with Electrons

AbstractChemical reduction of a benzo‐fused double [7]helicene (1) with two alkali metals, K and Rb, provided access to three different reduced states of 1. The doubly‐reduced helicene 12− has been characterized by single‐crystal X‐ray diffraction as a solvent‐separated ion triplet with two potassium counterions. The triply‐ and tetra‐reduced helicenes, 13− and 14−, have been crystallized together in an equimolar ratio and both form the contact‐ion complexes with two Rb+ ions each, leaving three remaining Rb+ ions wrapped by crown ether and THF molecules. As structural consequence of the stepwise reduction of 1, the central axis of helicene becomes more compressed upon electron addition (1.42 Å in 14− vs. 2.09 Å in 1). This is accompanied by an extra core twist, as the peripheral dihedral angle increases from 16.5° in 1 to 20.7° in 14−. Theoretical calculations provided the pattern of negative charge build‐up and distribution over the contorted helicene framework upon each electron addition, and the results are consistent with the X‐ray crystallographic and NMR spectroscopic data.

Quantitative assessment of the absorbed dose in cryodeposited noble-gas films under X-ray irradiation: Simulation vs. experiment

This work was aimed at quantitative determination of the absorbed doses under X-ray irradiation of cryogenic deposited films, particularly related to the matrix isolation experiment. The relative absorbed doses in the layers of solid noble gases of different thickness irradiated with an X-ray tube (46.6 kVp) in the specified cryostat geometry were calculated by Monte-Carlo simulation using a Geant4 code. In order to calibrate the obtained values, the relative absorbed dose in the ferrosulfate dosimeter irradiated in the same geometry was calculated in the same way. The effect of additional Al filter (420 μm) on the photon spectrum and relative absorbed dose in noble gas layers and dosimetric system was simulated. The experimental verification was based on the monitoring of the radiation-induced decay rate of ethane molecules isolated in different solid noble gas matrices (Ar, Kr, and Xe, 1:1000) irradiated in the cryostat at 6 K. It was shown that the simulation reproduces well the experimentally observed effect of the filter on relative absorbed dose rate in both dosimetric system and the layers of different solid noble gases (80–180 μm). Absolute absorbed dose rates were determined as a function of deposited layer thickness in different noble gases. The comparison of the simulation results with a crude estimation based on a single effective energy value is discussed.

Metal-Organic Framework Based on α-Cyclodextrin Gives High Ethylene Gas Adsorption Capacity and Storage Stability.

Two metal-organic framework (MOF) materials, that is, α-cyclodextrin (α-CD)-MOF-Na and α-CD-MOF-K, were successfully synthesized and exhibited excellent adsorption capacity and storage stability for ethylene gas. The ethylene encapsulation capacity of α-CD-MOF-Na and α-CD-MOF-K reached 47.4 and 52.9% (w/w), respectively, which was significantly higher than those of other materials reported such as α-CD and V-type starch. The release characteristics of ethylene inclusion complexes (ICs) were determined under different temperatures and relative humidity conditions. The ethylene gas could be stably encapsulated in α-CD-MOF-ethylene ICs at 25 °C for up to 30 days. The crystal structure of α-CD-MOFs was determined to explain their high capacity and stability for ethylene storage. Molecular simulation was used to model the location of ethylene molecules in α-CD-MOFs. Alpha-CD-MOF-Na and α-CD-MOF-K showed "8"-shaped and spindle-shaped cavity, respectively, which effectively adsorbed and stored the ethylene gas. Accelerated ripening experiments showed that 5 mg of α-CD-MOF ICs could ripen bananas within 4 days, with an effect similar to that of free ethylene gas. We suggest that α-CD-MOF materials are an excellent material for ethylene storage with potential application in industrial and agricultural areas.

Is ascorbic acid a key signaling molecule integrating the activities of 2-oxoglutarate-dependent dioxygenases? Shifting the paradigm

The integration of different environmental cues and the harmonization of proper responses require molecular communication at different levels. Enzymes belonging to the large superfamily of 2-oxoglutarate-dependent dioxygenases (2-ODDs) use for their catalytic activity different cofactors, including molecular oxygen, 2-oxoglutarate, and ascorbic acid (ASC). In plants, 2-ODDs are involved in the synthesis of hydroxyproline (largely present in cell wall proteins), gibberellins, ethylene, zeaxanthin, and many more relevant molecules. In addition, 2-ODDs operating in the epigenetic control of gene expression by regulating cytosine and histone methylation have been recently identified in both animals and plants. It is here hypothesized that each of the cofactors required for the complex catalytic mechanism of 2-ODDs provides specific molecular information. Such information is integrated by 2-ODDs, which in turn regulate the synthesis of information-bearing metabolites (e.g. hormones), and control epigenetic processes. The evolutionary success of the catalytic mechanism shared by 2-ODDs is possibly related to the parallel activation of different biosynthetic pathways.

Osmotin-Like Protein Gene from Panax notoginseng Is Regulated by Jasmonic Acid and Involved in Defense Responses to Fusarium solani.

Osmotin and osmotin-like proteins (OLPs) play important roles in plant defense responses. The full-length cDNA sequence of an OLP gene was cloned from Panax notoginseng using rapid amplification of cDNA-end technology and named PnOLP1. A quantitative reverse transcription-PCR analysis showed that the signaling molecules methyl jasmonate, salicylic acid, ethylene, and hydrogen peroxide induced PnOLP1 expression to different degrees. In addition, the expression level of PnOLP1 rapidly increased within 48 h of inoculating P. notoginseng with the root rot pathogen Fusarium solani. Subcellular localization revealed that PnOLP1 localized to the cell wall. A prokaryotic expression vector containing PnOLP1 was constructed and transformed into Escherichia coli BL21 (DE3), and in vitro antifungal assays were performed using the purified recombinant PnOLP1 protein. The recombinant PnOLP1 protein had strong inhibitory effects on the mycelial growth of F. oxysporum, F. graminearum, and F. solani. A plant PnOLP1-overexpression vector was constructed and transfected into tobacco, and the resistance of T2 transgenic tobacco against F. solani was significantly enhanced compared with wild-type tobacco. Moreover, a PnOLP1 RNAi vector was constructed and transferred to the P. notoginseng leaves for transient expression, and the decrease of PnOLP1 expression level in P. notoginseng leaves increased the susceptibility to F. solani. Thus, PnOLP1 is an important disease resistance gene involved in the defense responses of P. notoginseng to F. solani.

Use of a Copper- and Zinc-Modified Natural Zeolite to Improve Ethylene Removal and Postharvest Quality of Tomato Fruit

Ethylene stimulates ripening and senescence by promoting chlorophyll loss, red pigment synthesis, and softening of tomatoes and diminishes their shelf-life. The aim of this work was to study the performance of a novel copper- and zinc-based ethylene scavenger supported by ion-exchange on a naturally occurring zeolite by analyzing its ethylene adsorption capacity and the influence of ethylene scavenging on quality attributes during the postharvest life of tomatoes. The influence of copper- and zinc-modified zeolites on ethylene and carbon dioxide concentrations and postharvest quality of tomatoes was compared with unmodified zeolite. Interactions among ethylene molecules and zeolite surface were studied by diffuse reflectance infrared Fourier transform spectroscopy in operando mode. The percentage of ethylene removal after eight days of storage was 57% and 37% for the modified zeolite and pristine zeolite, respectively. The major ethylene increase appeared at 9.5 days for the modified zeolite treatment. Additionally, modified zeolite delayed carbon dioxide formation by six days. Zeolite modified with copper and zinc cations favors ethylene removal and delays tomato fruit ripening. However, the single use of unmodified zeolite should be reconsidered due to its ripening promoting effects in tomatoes at high moisture storage conditions, as water molecules block active sites for ethylene adsorption.

Isomerization and decomposition reactions of acetaldehyde relevant to atmospheric processes from dynamics simulations on neural network-based potential energy surfaces.

Acetaldehyde (AA) isomerization [to vinylalcohol (VA)] and decomposition (into either CO + CH4 or H2 + C2H2O) are studied using a fully dimensional, reactive potential energy surface represented as a neural network (NN). The NN, trained on 432 399 reference structures from MP2/aug-cc-pVTZ calculations, has a mean absolute error of 0.0453 kcal/mol and a root mean squared error of 1.186 kcal mol-1 for a test set of 27 399 structures. For the isomerization process AA → VA, the minimum dynamical path implies that the C-H vibration and the C-C-H (with H being the transferring H-atom) and the C-C-O angles are involved to surmount the 68.2 kcal/mol barrier. Using an excess energy of 93.6 kcal/mol-the typical energy available in the solar spectrum and sufficient to excite to the first electronically excited state-to initialize the molecular dynamics, no isomerization to VA is observed on the 500 ns time scale. Only with excess energies of ∼127.6 kcal/mol (including the zero point energy of the AA molecule), isomerization occurs on the nanosecond time scale. Given that collisional quenching times under tropospheric conditions are ∼1 ns, it is concluded that formation of VA following photoexcitation of AA from actinic photons is unlikely. This also limits the relevance of this reaction pathway to be a source for formic acid.

Destructive-quantum-interference suppression in crown ether single molecule junction

The electronic transmission coefficient of X-crown ether-Y (X = 3Y ;Y = 4, 5, and 6) have been investigated using density functional theory and Green’s function approximation incorporated with the Huckel method. The results illustrate unexpected role of the oxygen atoms to highly enhance charge transport in the crown ether molecules by moving the destructive quantum interferences (QI) close to the Fermi level. Such slight shifting creates a beneficial peak-valley pattern in the transmission spectra that facilitates the ON/OFF variation. Moreover, the length of the crown ether rings offers an insignificant impact on electronic transmission. Hence, we believe that these findings would deepen our understanding of QI patterns and exploit crown ether molecules more practically and efficiently in molecular devices.

Molecular Dynamic Simulations of Diethyl Ether and its Mixture with Cellulose Dinitrate Tripolymer Molecules for their Thermal Diffusion Behaviors

In this paper, thermal diffusion states of pure diethyl ether and its mixture with cellulose dinitrate tripolymer were uncovered by LAMMPS-based Molecular Dynamic (MD) simulations. Those MD simulations were generally performed through specified ReaxFF reactive force field to obtain the properties of the chemical system such as molecular energy, density, mean square displacement (MSD) and molecular coordinate. The result of MD simulations presented the clear superheating phenomenon of pure liquid diethyl ether system in the studied environment. The obtained phase transition point was much higher than the reported one. The deviation between two temperatures was about 132.369[Formula: see text]K. It was also demonstrated that the transition process was associated with the sharp increment of potential energy, volume, diffusion coefficient and cohesive energy. However, the split of these diethyl ether molecules was not uniform. The cluster-like transition state was observed before the end of the vaporing process (460[Formula: see text]K). As for the addition of cellulose dinitrate tripolymer, these molecules were not agglomerated in the simulated organic mixture. However, the diffusion of cellulose dinitrate tripolymer was much weaker than those diethyl ether molecules. While the concentration of cellulose dinitrate tripolymer was higher, molecular interactions of this organic mixture were consequently improved, and this further limited the diffusion behavior of the entire chemical system. It could be concluded that the diffusion behavior of the entire organic system was decreased with more amount of cellulose dinitrate tripolymer molecules.

Crystal structure of catena-poly[[[di-aqua-[1,2-bis(pyridin-4-yl)ethene]{4-[2-(pyridin-4-yl)ethen-yl]pyridinium}gold(I)iron(II)]-di-μ-cyanido] bis-[dicyanido-gold(I)] 1,2-bis-(pyridin-4-yl)ethene dihydrate

In the title compound [Fe(bpe)(Hbpe)Au(CN)2][Au(CN)2]2·bpe·2H2O} n [where bpe = 1,2-bis-(pyridin-4-yl)ethene, C12H10N2], the FeII ion is coordinated in a distorted octa-hedral [FeN4O2] environment by two di-cyano-aurate anions, two water mol-ecules and two partially protonated 1,2-di(4-pyrid-yl)ethyl-ene mol-ecules. Di-cyano-aurate anions bridge the FeII cations, forming infinite chains, which propagate along the a-axis direction. The chains are connected via aurophilic inter-actions with two non-coordinated di-cyano-aurate anions for each FeII ion. The polymeric chains inter-act with each other via π-π stacking between the guest bpe mol-ecules and multiple hydrogen bonds.

Quantum Chemistry-Informed Active Learning to Accelerate the Design and Discovery of Sustainable Energy Storage Materials

We employed density functional theory (DFT) to compute oxidation potentials of 1400 homobenzylic ether molecules to search for the ideal sustainable redoxmer design. The generated data were used to...