Presence Of Ether Research Articles

Alteration of lipid bilayer mechanics by volatile anesthetics: Insights from μs-long molecular dynamics simulations

SummaryVery few drugs in clinical practice feature the chemical diversity, narrow therapeutic window, unique route of administration, and reversible cognitive effects of volatile anesthetics. The correlation between their hydrophobicity and their potency and the increasing amount of evidence suggesting that anesthetics exert their action on transmembrane proteins, justifies the investigation of their effects on phospholipid bilayers at the molecular level, given the strong functional and structural link between transmembrane proteins and the surrounding lipid matrix. Molecular dynamics simulations of a model lipid bilayer in the presence of ethylene, desflurane, methoxyflurane, and the nonimmobilizer 1,2-dichlorohexafluorocyclobutane (also called F6 or 2N) at different concentrations highlight the structural consequences of VA partitioning in the lipid phase, with a decrease of lipid order and bilayer thickness, an increase in overall lipid lateral mobility and area-per-lipid, and a marked reduction in the mechanical stiffness of the membrane, that strongly correlates with the compounds' hydrophobicity.

Investigation of the LDPE dust flame propagation effected by the ethylene concentration

The presence of ethylene (C2H4) gas in a low-density polyethylene (LDPE) combustion process increases the severity of the dust explosion. Understanding dust explosion propagation as influenced by C2H4 concentration is important to characterise the severity of the LDPE dust explosion. Therefore, this paper aims to study the explosion propagation mechanism as influenced by ethylene concentration in LDPE combustion using computational fluid dynamic (CFD) ANSYS FLUENT simulation. Results showed that ethylene concentration influenced the LDPE/C2H4 flame propagation mechanism by increasing the equivalence ratio (ER) to 1.2. The severity of LDPE/C2H4 explosion was also recorded at C2H4 concentration, at ER = 1.2 with explosion pressure = 5.5 bar respectively.

Exploring the reaction pathway involved in the dibenzo‐18‐crown‐6 synthesis from catechol and bis(2‐chloroethyl) ether in presence of base

AbstractComputational investigations reported in this work have proposed the mechanism involved in the synthesis of dibenzo‐18‐crown‐6 (DB18C6) from catechol and bis(2‐chloroethyl) ether in presence of base. The transition states on the reaction path have been identified, and the corresponding barrier heights are estimated. Paths related to the side‐product formations, such as benzo‐9‐crown‐3 and 1,2‐bis[2‐(2‐chloroethoxy)ethoxy]‐benzene, have been also tracked. The cation‐assisted (Na+ and K+ ions) cyclization process (template effect) creates more structurally ordered reactant and transition state species. This facilitates the cyclization step that is an intramolecular SN2 process. Additionally, it eliminates possibilities of different side‐product formations giving better yield of the crown ether, as reported previously. This cyclization step has a comparatively lower barrier height for Na+ system (by 3 kcal/mol) in gas phase than K+ system; however, it becomes reverse in 1‐butanol where the barrier height is almost 2.5 kcal/mol lower during the K+DB18C6 formation. Consequently, a faster cyclization has been found in this solvent from the reaction rate studies for the potassium system. This is in‐line with the experimental observations reported on the alkali‐metal‐catalyzed benzo‐18‐crown‐6 ether formation reactions. The dipole moment value of the transition state involved in this step for the larger alkali metal ion system is found to be significantly higher (by 5–8 D) than the reactant species.

Measurement and analysis of interfacial tension of decane/water system pressurized with methane + ethane + propane gas mixture

Blockages in natural gas and oil pipelines can be caused by the aggregation of clathrate hydrate crystals which form at the oil-water-gas interfaces. Knowledge of interfacial tensions between components are crucial to understanding the interface physical chemistry and numerically simulating pipeline multiphase flow. This study measures the effect of the presence of natural gas components on the oil-water interfacial tension and its potential implications on flow assurance in oil-gas pipelines. Decane is used to mimic oil and is saturated with the gaseous mixture of methane, ethane, and propane as is consistent with simulations of multiphase dynamics. Water droplets were generated in decane and photographed through a window using pendant drop method in order to determine the oil-water interfacial tension. This study examined both mechanical and thermodynamic phenomena by considering interfacial tension under different pressure/temperature conditions covering the natural gas hydrate formation region. The effect of the gas mixture composition and pressure on the interfacial tension was determined at different temperatures in the range of pipeline operating conditions. The behavior was explained from both experimental and theoretical points of view. At lower pressures, the presence of the C2 and C3 natural gas components lowers the decane-water interfacial tension compared to the case of the decane-water-methane system. In particular, the pressure dependence of the interfacial tension was found to be almost five times higher than that in the absence of C2 and C3. By decreasing the interfacial tension, the presence of ethane and propane may facilitate the mixing of the water and oil phases in pipelines, therefore affecting the rate of hydrate formation.

Identification of Adsorbed Species and Surface Chemical State on Ag(111) in the Presence of Ethylene and Oxygen Studied with Infrared and X-ray Spectroscopies

Using a combination of two surface-sensitive spectroscopy techniques, the chemical state of the Ag(111) surface and the nature of the adsorbed species in the presence of ethylene and oxygen gases are identified. In the 10 mbar pressure range and 25–200 °C studied here, Ag(111) remains largely metallic even in O2-rich conditions. The only adsorbed molecular species with a low but discernible coverage is surface carbonate, which forms due to further oxidation of produced CO2, in a similar manner to its formation in ambient air on Ag surfaces. Its formation is also pressure-dependent, for instance, it is not observed when the total pressure is in the 1 mbar pressure range. Production of carbonate, along with carbon dioxide and water vapor as the main gas-phase products, suggests that an unpromoted Ag(111) surface catalyzes mainly the undesired full oxidation reaction.

Role of ethylene and proteolytic N-degron pathway in the regulation of Arabidopsis seed dormancy.

Primary dormant seeds of Arabidopsis thaliana did not germinate in darkness at temperature higher than 10-15°C. Ethylene improved the germination of dormant wild-type (Col-0) seeds at 25°C in darkness but seeds of the mutant affected in the proteolytic N-degron pathway, proteolysis6 (prt6), were insensitive to ethylene suggesting that PRT6 was involved in dormancy release by ethylene. The substrates of the N-degron pathway, the Ethylene Response Factors from group VII (HRE1, HRE2, RAP2.2, RAP2.3, and RAP2.12), were identified to be involved in this insensitivity with an increased germination in prt6 rap2.2 rap2.3 rap2.12 rather than in prt6 hre1 hre2, which also indicated that the three RAPs acted downstream of PRT6, while the two HREs acted upstream of PRT6. Ethylene reduced the expression of the three RAPs in Col-0 seeds but they were maintained or induced by ethylene in prt6 seeds. The promoting effect of ethylene was associated with a down-regulation of dormancy-related genes in gibberellins (GAs) and abscisic acid (ABA) signaling, such as RGA, RGL2, and ABI5, and with a strong decrease in ABA/GA4 ratio in the presence of ethylene. In contrast, we show that the insensitivity of prt6 seeds to ethylene was mainly related to GA signaling disturbance.

Synthesis, Characterization, and Reaction Studies of Pd(II) Tripeptide Complexes.

The aqueous synthesis of Pd(II) complexes with alkylated tripeptides led to the hydrolysis of the peptides at low pH values and mixtures of complexed peptides were formed. A non-aqueous synthetic route allowed the formation and isolation of single products and their characterization. Pd(II) complexes with α-Asp(OR)AlaGly(OR), β-Asp(OR)AlaGly(OR), and TrpAlaGly(OR) (R = H or alkyl) as tri and tetradentate chelates were characterized. The tridentate coordination mode was accompanied by a fourth monodentate ligand that was shown to participate in both ligand exchange reactions and a direct removal to form the tetradentate coordination mode. The tetradentate coordination revealed a rare a hemi labile carbonyl goup coordination mode to Pd(II). Reactivity with small molecules such as ethylene, acids, formate, and episulfide was investigated. Under acidic conditions and in the presence of ethylene; acetaldehyde was formed. The Pd(II) is a soft Lewis acid and thiophilic and the complexes abstract sulfur from episulfide at apparent modest catalytic rates. The complexes adopt a square planar geometry according to a spectroscopic analysis and DFT calculations that were employed to evaluate the most energetically favorable coordination geometry and compared with the observed infrared and NMR data.

Transition Metal-Catalyzed C-H Oxidation of Saturated Hydrocarbons with Molecular Oxygen.

The C-H oxidation of saturated hydrocarbons to the corresponding alcohols and ketones can be performed efficiently at room temperature with molecular oxygen (1 atm) in the presence of acetaldehyde and catalysts such as Fe, Cu(OH)2 , and CuCl2 -18-crown-6 complex. Moreover, extremely high turnover numbers (>27,000) have been obtained for the C-H oxidation of saturated hydrocarbons with molecular oxygen (1 atm) using a combination of Cu(OAc)2 and acetonitrile at 70 °C. Related oxidation reactions such as epoxidation, Baeyer-Villiger reaction, acetoxylation of β-lactams with molecular oxygen and a suitable aldehyde at room temperature are described.

Spectroscopic Signature and Structure of the Active Sites in Ziegler-Natta Polymerization Catalysts Revealed by Electron Paramagnetic Resonance.

Despite decades of extensive studies, the atomic-scale structure of the active sites in heterogeneous Ziegler-Natta (ZN) catalysts, one of the most important processes of the chemical industry, remains elusive and a matter of debate. In the present work, the structure of active sites of ZN catalysts in the absence of ethylene, referred to as dormant active sites, is elucidated from magnetic resonance experiments carried out on samples reacted with increasing amounts of BCl3 so as to enhance the concentration of active sites and observe clear spectroscopic signatures. Using electron paramagnetic resonance (EPR) and NMR spectroscopies, in particular 2D HYSCORE experiments complemented by density functional theory (DFT) calculations, we show that the activated ZN catalysts contain bimetallic alkyl-Ti(III),Al species whose amount is directly linked to the polymerization activity of MgCl2-supported Ziegler-Natta catalysts. This connects those spectroscopic signatures to the active species formed in the presence of ethylene and enables us to propose an ethylene polymerization mechanism on the observed bimetallic alkyl-Ti(III),Al species based on DFT computations.

Regulation of Botrytis cinerea Infection and Gene Expression in Cut Roses by Using Nano Silver and Salicylic Acid.

Botrytis cinerea (B. cinerea) is one of the necrotrophic pathogens resulting in the heaviest commercial losses in cut rose flowers, and the severity of gray mold disease partly depends on the presence of ethylene during the storage and transport. The effectiveness of nano silver (NS) and salicylic acid (SA) was assessed as a novel control agent in protecting the cut rose flowers against B. cinerea infection and ethylene damages. The efficacy of NS and SA was compared with an inoculated control (CON). A non-treated control (NT) was also used to evaluate the natural infection process. The results indicated that pretreatment with 20 mg L−1 NS significantly reduced B. cinerea growth in rose petals during vase periods. NS effectively suppressed the mRNA levels of ethylene biosynthesis genes (RhACS2, RhACS4, and RhACO1) and the reduction in expression levels of ethylene receptor genes (RhETR1, RhETR2, and RhETR5) and the downstream regulator RhCTR2 in rose petals after B. cinerea inoculation. NS application also decreased the expression of the B. cinerea snod-prot-like 1 (Bcspl1) gene which acts as the virulence factor in cut roses. In NS flowers, the maximum quantum yield of PSII (Fv/Fm) value was higher and the leaf temperature was lower on day 1, suggesting that these factors can be used for detecting B. cinerea infection and water stress in cut rose flowers. Furthermore, NS improved water relations and extended the vase life of cut rose flowers by 3.3 d, compared with that of NT flowers. In contrast, SA had no inhibitive effects on both B. cinerea growth and ethylene response in cut roses. The findings from the present study highlight NS as a promising new candidate for preventing B. cinerea infection and ethylene damages and for improving the postharvest quality of cut roses exported overseas.

Influence of defoaming agents on mechanical performances and pore characteristics of Portland cement paste/mortar in presence of EVA dispersible powder

The present study reports the influence of defoaming agent (DA) on the mechanical performances and pore characteristics of cement paste/mortar in presence of ethylene and vinyl acetate copolymer (EVA) dispersible powder. To make a comparative investigation, two various types of DA including silicone and ether DA are introduced. Fluidity, air content, volume density and strengths experiments are performed to evaluate the development of workability and mechanical performances. The hydration kinetics, phase composition and pore structure are characterized by isothermal calorimetry (ICC), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and mercury intrusion porosimetry (MIP) techniques. The experimental results indicate that the initial fluidity is increased with addition of EVA, while it is decreased with the content of defoaming agents. The DA enhances the development of strengths and volume density of hardened paste/mortar in presence of EVA. The fact that EVA participates in the chemical reaction and promotes the formation of carboxyl-containing substance (e.g. calcium acetate), ettringite and calcium hydroxide can be found. MIP results shows that the porosity and more-harmful pore are increased with the incorporation of EVA. DA significantly reduces the porosity and quantity of more-harmful pore, contributing to the higher mechanical properties. This study can be viewed as a valuable reference for the improvement of pore structure by using DA in the EVA modified cement-based materials.

The first record of the genus Lamellibrachia (Siboglinidae) tubeworm along with associated organisms in a chemosynthetic ecosystem from the Indian Ocean: A report from the Cauvery–Mannar Basin

Here, we report for the first time, the genus Lamellibrachia tubeworm and associated chemosynthetic ecosystem from a cold-seep site in the Indian Ocean. The discovery of cold-seep was made off the Cauvery–Mannar Basin onboard ORV Sindhu Sadhana (SSD-070; 13th to 22nd February 2020). The chemosymbiont bearing polychaete worm is also associated with squat lobsters (Munidposis sp.) and Gastropoda belonging to the family Buccinidae. Relict shells of chemosynthetic Calyptogena clams are ubiquitous at the seep sites. The Lamellibrachia tubes were found to be firmly anchored into the authigenic carbonate crusts. The authigenic carbonate crusts (chemoherm) are packed with large Calyptogena shells (whole shell and fragments). Very high concentrations (3800–12900 µM) of hydrogen sulfide (H2S) in the interstitial waters (40 cmbsf) is responsible for the sustenance of chemosymbiont bearing tubeworms. The posterior end of the tube penetrates downwards into the H2S-rich zone. The high concentration of H2S at ~40 cmbsf is attributed to sulfate reduction via anaerobic oxidation of methane (AOM) pathway. Methane hydrate was observed within the faults/fractures in the sediments. The presence of ethane and propane along with methane in the headspace gases and δ13CCH4 values (–28.4 to –79.5‰ VPDB) suggest a contribution of deep-seated thermogenic methane.

Formation and Behavior of Carbonates on Ag(110) in the Presence of Ethylene and Oxygen

Intermediate species formed on Ag(110) surfaces under the presence of ethylene and oxygen in the sub-Torr pressure range were studied by near-ambient-pressure X-ray photoelectron spectroscopy (XPS)...

On the photolysis branching ratio of methyl ethyl ketone

The methyl ethyl ketone (MEK) photolysis branching ratio (α) was re-evaluated by an end product analysis and box model simulations with the Master Chemical Mechanism (MCM). Using light emitting diodes centered at 285 nm or 315 nm, MEK was irradiated in the presence of nitric oxide and oxygen to produce peroxyacetic and peroxypropanoic nitric anhydride, CH3C(O)O2NO2 (PAN) and C2H5C(O)O2NO2 (PPN), which were quantified by gas chromatography. Box model simulations indicated that PPN is partially produced as a secondary product from chemistry initiated by reaction of the hydroxyl radical (OH) with MEK. Under NOx-limited experimental conditions or in the presence of ethane as an OH quencher, the product distribution observed required α = (7 ± 1)% + (1.1 ± 0.7) × 10−4 × (T-298) for 250K < T < 300K (2σ uncertainty), independent of pressure (at pressures > 266 hPa) and consistent with current IUPAC recommendations.

Analytical examination of alcohol-based hand disinfectants in our country and evaluation with respect to COVID-19 pandemic

Objectives: The use of alcohol-based hand disinfectants (ABHD) is recommended in the COVID-19 pandemic. This study, it was aimed to analyze the content of ABEDs in our country and to discuss the findings in the light of literature. Materials and Methods: ABHDs in our country were searched on the Google search engine. Content information of the commercial product was saved. Data were analyzed under 5 headings: according to the alcohol ratio, the presence of ethyl and/or isopropyl alcohol, the presence of other disinfectants, the presence of the moisturizer, and the formulation recommended according to the World Health Organization (WHO). Results: The most frequently observed alcohol ratios were as follows: 70%, 75%, 65%, and 80%. 21% of the products have only ethanol, 15% have only isopropyl alcohol, 34% have ethanol and isopropyl alcohol. Hydrogen peroxide was observed in 6.5% of the products. 44% of the products had glycerin, 10% had glycerin and lanolin. The formulation suggested by WHO was exactly observed in one product. Conclusion: Sars-CoV-2 virus can be inactivated by ethanol (> 75%) and isopropanol (> 70%). One of the WHO formulations contain 80% ethanol and the other 75% isopropanol. The alcohol ratio was 70% and above in more than half of ABHDs in our country. These were ethyl and/or isopropyl alcohol. Only one product complied with the WHO formulation. As a result, the most important step for hand hygiene in the COVID-19 pandemic should be the selection of ABHD with the appropriate formulation. © 2021 Ankara Yildirim Beyazit University.

Yttrium stabilization and Pt addition to Pd/ZrO2 catalyst for the oxidation of methane in the presence of ethylene and water.

Catalytic oxidation is the most efficient method of minimizing the emissions of harmful pollutants and greenhouse gases. In this study, ZrO2-supported Pd catalysts are investigated for the catalytic oxidation of methane and ethylene. Pd/Y2O3-stabilized ZrO2 (Pd/YSZ) catalysts show attractive catalytic activity for methane and ethylene oxidation. The ZrO2 support containing up to 8 mol% Y2O3 improves the water resistance and hydrothermal stability of the catalyst. All catalysts are characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), O2-temperature-programmed desorption (O2-TPD), and CO-chemisorption techniques. It shows that high Pd dispersion and Pd–PdO reciprocation on the Pd/YSZ catalyst results in relatively high stability. In situ diffuse reflectance infrared Fourier-transform (DRIFT) experiments are performed to study the reaction over the surface of the catalyst. Compared with bimetallic catalysts (Pd : Pt), the same amounts of Pd and Pt supported on ZrO2 and Y2O3-stabilized ZrO2 catalysts show enhanced activity for methane and ethylene oxidation, respectively. A mixed hydrocarbon feed, containing methane and ethylene, lowers the CH4 light-off temperature by approximately 80 °C. This shows that ethylene addition has a promotional effect on the light-off temperature of methane.

Ethanol vapor treatment inhibits apple ripening at room temperature even with the presence of ethylene

Abstract The present study aimed to evaluate the effect of two ethanol vapor doses (250 and 500 ppm), 1-methylcyclopropene (1-MCP) (0.650 ppm) with or without ethylene application (150 ppm) on the aerobic and anaerobic metabolism and quality of ‘Elstar’, a fast ripening apple cultivar, and ‘Nicoter’, a slowly ripening apple cultivar, over 14 d of holding at room temperature (20 ± 2 °C). Fruit were subjected to treatments for 24 h and analyses performed after 0, 7 and 14 d holding at room temperature (20 ± 2 °C). For both cultivars studied, ethanol vapor treatments, especially 500 ppm, inhibited the ripening of apples even when combined with 150 ppm of ethylene, but not as much as 1-MCP treatment in ‘Nicoter’ apples. Fruit treated with ethanol vapor maintained lower electrolyte leakage, higher flesh firmness, greener color and had more healthy fruit. However, its application increased the pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activity, acetaldehyde and ethyl acetate accumulation, but in concentrations below the odor threshold reported in the literature. The 1-MCP treatment increased decay incidence, reducing the healthy fruit amount in ‘Nicoter’ apples after 14 d, but maintained a very low ethylene production and respiration rate, which allowed higher acidity maintenance after 14 d holding at room temperature. There was no incidence of external and internal physiological disorders in both cultivars.

Ring-closing metathesis of prochiral oxaenediynes to racemic 4-alkenyl-2-alkynyl-3,6-dihydro-2H-pyrans.

The prochiral 4-(allyloxy)hepta-1,6-diynes, optionally modified in the positions 1 and 7 with an alkyl or ester group, undergo a chemoselective ring-closing enyne metathesis yielding racemic 4-alkenyl-2-alkynyl-3,6-dihydro-2H-pyrans. Among the catalysts tested, Grubbs 1st generation precatalyst in the presence of ethene (Mori conditions) gave superior results compared to the more stable Grubbs or Hoveyda–Grubbs 2nd generation precatalysts. This is probably caused by a suppression of the subsequent side-reactions of the enyne metathesis product with ethene. On the other hand, the 2nd generation precatalysts gave better yields in the absence of ethene. The metathesis products, containing both a triple bond and a conjugated system, can be successfully orthogonally modified. For example, the metathesis product of 5-(allyloxy)nona-2,7-diyne reacted chemo- and stereoselectively in a Diels–Alder reaction with N-phenylmaleimide affording the tricyclic products as a mixture of two separable diastereoisomers, the configuration of which was estimated by DFT computations. The reported enediyne metathesis paves the way to the enantioselective enyne metathesis yielding chiral building blocks for compounds with potential biological activity, e.g., norsalvinorin or cacospongionolide B.

IMPACT OF ETHANOL, METHANOL AND SULFIDES ON THE NITRIFICATION PROCESS OF AMMONIUM IONS IN NATURAL WATERS

This paper includes the results of laboratory modeling of ethyl and methyl alcohol and sulfide ions impact on the biochemical process of ammonium ions nitrification in water from the Dniester River, Palanca village, Stefan Voda district (august 2019). An insignificant influence of ethyl and methyl alcohol (0,5 ml/L) was established in both stages of the process. In the comparison test, the stage NH4 + → NO2 - lasted 12 days, and in the presence of ethyl alcohol - 14 days and in the presence of methyl alcohol - 16 days. The NO2 - → NO3 - stage in the comparison test lasted 16 days and in the presence of ethyl alcohol 2 days less (14 days) and in the presence of methyl alcohol - 16 days, so without any influence. The study showed a significant influence of sulfur ion in both stages at a concentration of 0.1 mg/L with and without the presence of ethyl and methyl alcohol. In the comparison test, the NH4 + → NO2 - stage lasted 12 days, in the presence of the S2- ion it lasted 18 days, and in the presence of alcohols and sulfur ion - more than 20 days, the synergism of the impact being obvious. In the NO2 - → NO3 - step of the process for 20 days the NO2 - concentration did not decrease in the presence of the S2- ion, and in the presence of ethyl, methyl alcohol and S2- only 15-35% of the NO2 - ions were oxidized, in comparison with the witness test.

Detection and identification of ethanal-derived spin-trapped free radicals using headspace thermal desorption gas chromatography-mass spectrometry (TD-GC-MS)

In this study, we demonstrate a novel approach to the detection and identification of the products of spin-trapped free radicals. Hydroxyl free radicals were generated by Fenton-based chemistry in the presence of ethanal and the spin-trapping agent N-tert-butyl-α-phenylnitrone (PBN). The resulting volatile compounds present in the reaction vial headspace were collected using thermal desorption (TD) and analysed by gas chromatography-mass spectrometry (GC-MS). Eleven compounds were detected in the headspace, and their identification was aided by using either a fluorinated or deuterated analogue of PBN as an alternative spin trap and/or deuterated ethanal (CD3CHO) as the secondary source of free radicals. The electron-ionisation (EI) mass spectra clearly demonstrate the “capture” of methyl radicals; two of the compounds detected were identified as containing one methyl group derived from ethanal, and four were shown to contain two methyl groups. This study demonstrates that sampling the reaction headspace using TD-GC-MS is a viable method for analysing products of free radical trapping, and potentially may be applied to a wide range of free radical systems.