Mixture Of Ether Research Articles

Investigation of Molecular Interaction in Binary Liquid Mixtures of some Cyclic Ether with N-Alkanols at 298.15K: By Ultrasonic Velocity Measurements

In the present study, we reported the densities and excess molar volumes and (V_m^E) excess acoustical impedance (ZE) for the pure organic solvent mixtures such as 1,3-Dioxolane + Pentanol, 1,3-Dioxolane + Hexanol, 1,3-Dioxolane + Heptanol, 1,3-Dioxolane + Octanol, 1,3-Dioxolane + Nonanol and 1,3-Dioxolane + Decanol at 298.15K. Excess molar volumes (V_m^E) excess acousticimpedance (ZE) for these binary mixtures were calculated from the experimental density and sound velocity data and fitted to the Redlich-Kister polynomial equation to check the accuracy of experimental data. In addition, the interactions between the unlike molecules in the mixtures were confirmed by using the experimental results. It has been observed that, weak dispersive type intermolecular interactions are confirmed in the systems investigated. Dipole inducement is found to be more predominant in the system. The results are interpreted in terms of molecular interaction between the components of the mixture.

Methane, Ethane, and Propane Detection Using a Quartz-Enhanced Photoacoustic Sensor for Natural Gas Composition Analysis.

A compact and portable gas sensor based on quartz-enhanced photoacoustic spectroscopy (QEPAS) for the detection of methane (C1), ethane (C2), and propane (C3) in natural gas (NG)-like mixtures is reported. An interband cascade laser (ICL) emitting at 3367 nm is employed to target absorption features of the three alkanes, and partial least-squares regression analysis is employed to filter out spectral interferences and matrix effects characterizing the examined gas mixtures. Spectra of methane, ethane, and propane mixtures diluted in nitrogen are employed to train and test the regression algorithm, achieving a prediction accuracy of ∼98%, ∼96%, and ∼93% on C1, C2, and C3, respectively. With respect to previously reported QEPAS sensors for natural gas analysis, the high prediction accuracy as well as the capability to discriminate and detect C3 within natural gas-like complex mixtures provided by the employment of partial least-squares regression mark significant improvements. Furthermore, these results enable an improved performance of the sensor for in situ, real-time, and online natural gas composition analysis.

Propagation characteristics of stable detonation waves in curved channels with the lateral expansion effect

When a stable detonation wave propagates in a curved channel, it will be influenced by the curvature of the channel, which has been investigated in previous studies. Actually, propagation of a stable detonation wave in a curved channel becomes more unstable if the lateral expansion effect is introduced. However, this is an objective phenomenon in practical rotating detonation chambers. In order to clarify the impacts of the channel curvature and the lateral expansion on the propagation of stable detonation waves, this study has been carried out using a mixture of ethylene, oxygen, and nitrogen. The effects of the channel curvature, the detonable mixture height, and the equivalence ratio on the propagation characteristics in both confined and semi-confined curved channels have been focused in this experimental work. The propagation process was recorded by high-speed photography, and the cell width was obtained using the smoke visualization method, while the peak pressures near the outer wall were also measured. The results imply that the deficits of wave velocity and peak pressure are magnified when introducing the lateral expansion phenomenon, especially under fuel-lean and fuel-rich conditions. Meanwhile, the channel curvature and the mixture height also have a great impact on the detonation propagation. Five propagation modes have been observed after the stable detonation waves enter the curved channels with a semi-confined configuration, i.e., a stable mode, a critical mode, a weakly unstable mode, a highly unstable mode, and a deflagration mode. In addition, for the two observed unstable modes, decoupling occurs periodically near the inner wall. Finally, the critical conditions of the stable detonation mode in the semi-confined channel have been clarified. The critical inner radius should be 13.10–15.24 times of the average cell width, and meanwhile, the minimum detonable mixture height is equivalent to 7.03–8.12 times of the average cell width.

Method Development and Clinical Utility for Simultaneous Measurement of 21-Deoxycortisol, 17-Hydroxyprogesterone, Cortisol, and Cortisone Levels in Human Plasma Using UHPLC-MS/MS.

A simple and efficient validated assay for quantifying 21-deoxycortisol (21-DOC), 17-hydroxyprogesterone (17-OHP), cortisol, and cortisone in human plasma has been developed using ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS). Analysis of plasma samples were performed on Atlantis dC18 (3 μm) column using a mobile phase of 20.0 mM ammonium acetate and acetonitrile (50:50, v : v) that was delivered at isocratic flow rate 0.3 mL/minute. After addition of d4-cortisol as an internal standard (IS), plasma samples containing 21-DOC, 17-OHP, cortisol, and cortisone were extracted with mixture of dichloromethane and tert-butylmethyl ether 1:2 (v/v). Analytes were detected and quantified in the positive ion mode of electrospray ionization using multiple reaction monitoring transition set at mass to charge (m/z): 347.17 ⟶ 311.12, 331.17 ⟶ 96.97, 363.11 ⟶ 121.00, 361.18 ⟶ 163.11, and 367.19 ⟶ 121.24 for 21-DOC and 17-OHP, cortisol, cortisone, and cortisol-d4 (IS), respectively. The relationship between concentration and peak area response (analyte/IS) were linear over the range of 0.25-50, 0.5-100, 1-200, and 2-400 ng/mL for 21-DOC, 17-OHP, cortisone, and cortisol, respectively. The mean extraction recovery of the analytes was in the range of 83%-96%. The coefficient of variation within and between days was less than 13.6%, and the bias ranged from -9.2% to 12%. The measured level of cortisol, cortisone, and 17-OHP was in the range of 21.9-110, 4.33-12.71, and 0.37-1.4 ng/mL, respectively. Furthermore, the measured value of cortisone-cortisol ratio was in the range of 0.08-0.21.

A simple HPLC method for the determination of plasma progesterone levels in the third trimester of human pregnancy.

Progesterone is a steroid hormone primarily associated with pregnancy. A simple, rapid, and reliable high-performance liquid chromatography (HPLC) method has been developed and validated for the quantification of progesterone in human plasma. The method consists of a simple liquid-liquid extraction of progesterone and internal standard (estriol) from human plasma using a mixture of hexane and diethyl ether. The chromatographic determination of progesterone was performed using an acetonitrile-water (70:30, v/v) mobile phase with a C18 reversed-phase column. The method achieved an extraction recovery of greater than 96.4% from spiked plasma samples. Intra- and inter-day precision were generally acceptable, with relative SD% less than ≤6.60% and accuracy (relative error %) better than 3.64%. The developed and validated method was used to successfully quantify progesterone levels in plasma samples collected from women during the third trimester of pregnancy. Furthermore, a statistical comparison was conducted between progesterone concentrations in plasma samples obtained from 2 groups of pregnant women: group 1 (n = 9) at 30-35 weeks and group 2 (n = 9) at 36-41 weeks. The developed and validated HPLC method described in this study enables the successful determination of progesterone in human plasma, offering advantages such as shorter analysis time, simplicity, cost-effectiveness, and potential routine use during pregnancy.

Efficient Method of (S)-Nicotine Synthesis.

Improved methods for the synthesis of nicotine are of great importance due to the wide range of applications of synthetic nicotine, which is free from contamination with nitrosamines. Herein, we present a four-step chemical synthesis of (S)-nicotine, involving the reduction in myosmine, enantiomeric separation of nornicotine, and subsequent methylation of the appropriate enantiomer of nornicotine obtained. The reduction in myosmine was investigated using both electrochemical and chemical approaches, achieving up to 90% yields of pure nornicotine. To achieve the enantioseparation of nornicotine, its diastereomeric salts with chiral acids, specifically, N-lauroyl-(R)-alanine, were obtained in a mixture of methyl tert-butyl ether (MTBE) and chloroform, which led to the isolation of (S)-nornicotine with 92% ee. The structures of the obtained salts were determined by the X-ray diffraction (XRD) technique, which helped to explain the origin of enantiodiscrimination during the crystallization. The described methodology allows efficient regeneration of the reagents and solvents used, leading to cost-effective production of (S)-nicotine suitable for industrial-scale applications.

Exposure to an environmentally representative mixture of polybrominated diphenyl ethers (PBDEs) alters zebrafish neuromuscular development

Polybrominated diphenyl ethers (PBDEs) are a prevalent group of brominated flame retardants (BFRs) added to several products such as electronics, plastics, and textiles to reduce their flammability. They are reported as endocrine disruptors and neurodevelopmental toxicants that can accumulate in human and wildlife tissues, thus making their ability to leach out of products into the environment a great cause for concern. In this study, zebrafish (Danio rerio) embryos and larvae were exposed to a wide concentration range (1.5, 15, 150 and 300 pM) of a PBDE mixture from one to six days post-fertilization (dpf). Hatching rates, mortality and general morphology were assessed during the exposure period. A delay in hatching was observed at the two highest PBDEs concentrations and mortality rate increased at 6 dpf. By 4 dpf, larvae exposed to 150 pM and 300 pM PBDEs developed an upcurved phenotype. Analysis of motor behavior at 6 dpf revealed that PBDE exposure acutely reduced locomotion. To further analyze these motor deficits, we assessed the neural network density and motor neuron and neuromuscular junctions (NMJ) development by immunostaining and imaging. Acetylated α-tubulin staining revealed a significant loss of neurons in a dose-dependent manner. Synaptic vesicle protein 2 (SV2) and ⍺-bungarotoxin (⍺-BTX) staining revealed a similar pattern, with a significant loss of SV2 and nicotinic acetylcholine receptors, thus preventing the colocalization of presynaptic neurons with postsynaptic neurons. Consistent with these results, the presence of cleaved caspase-3 and acridine orange positive cells showed increased cell death in zebrafish larvae exposed to PBDEs. Our results suggest that exposure to PBDEs leads to deficits in the zebrafish neuromuscular system through neuron death, inducing morphological and motor deficiencies throughout their development. They provide valuable insight into the neurotoxic effects of PBDEs, further highlighting the relevance of the zebrafish model in toxicological studies.

Vapor-liquid-liquid equilibria for the water + 1-butanol + CPME mixture

In this contribution we have carried out vapor-liquid-liquid equilibrium (VLLE) determinations for the Water + 1-Butanol + cyclopenthyl methyl ether (CPME) mixture, where no previous information is reported. Measurements were performed with a commercial Fisher VLE/VLLE 602 equilibrium cell at 101.3 kPa and the Wisniak's L/K test is used to ensure the thermodynamic consistency for the two pairs of V-La and V-Lo phases at VLLE. Additionally, we have predicted the three-phase line of this system by performing modified multiphase flash calculations coupled with a phase stability restriction, where the system was modelled with the SAFT-VR-Mie equation of state. The VLLE of the ternary mixture was excellently predicted by only fitting binary interaction parameters to the phase equilibrium of each constituent binary mixture. This system has two partially miscible binaries in Water + 1-Butanol and Water + CPME, which makes the ternary liquid-liquid system a type II equilibrium envelope. The two binaries are connected through a zeotropic three-phase line.

Ethane Triggered Gate‐Opening in a Flexible−Robust Metal−Organic Framework for Ultra‐high Purity Ethylene Purification

Priority recognition separation of inert and larger ethane molecules from high‐concentration ethylene mixtures instead of traditional thermodynamic or size sieving strategy is a fundamental challenge. Herein, we report the ethane triggered gate‐opening in the flexible‐robust metal−organic framework Zn(ad)(min), the 3‐methylisonicotinic acid ligand can spin as a flexible gate when adsorbing the cross‐section well‐matched ethane molecule, thus achieving the unprecedent ethane adsorption capacity (62.6 cm3 g‐1) and ethane/ethylene uptake ratio (3.34) under low‐pressure region (0.1 bar and 298 K). The ethane‐induced structural transition behavior is uncovered by a collaboration of single‐crystal X‐ray diffraction, in‐situ variable pressure X‐ray diffraction and theoretical calculations, elucidating the synergetic mechanism of cross‐section matching and multiple supramolecular interactions within the tailor‐made pore channels. Dynamic breakthrough experiments revealed the outstanding separation performance of Zn(ad)(min) in the production of ultra‐high purity ethylene (> 99.995%) with a productivity of up to 39.2 L/kg under ambient conditions.

Ethane Triggered Gate-Opening in a Flexible-Robust Metal-Organic Framework for Ultra-high Purity Ethylene Purification.

Priority recognition separation of inert and larger ethane molecules from high-concentration ethylene mixtures instead of traditional thermodynamic or size sieving strategy is a fundamental challenge. Herein, we report the ethane triggered gate-opening in the flexible-robust metal-organic framework Zn(ad)(min), the 3-methylisonicotinic acid ligand can spin as a flexible gate when adsorbing the cross-section well-matched ethane molecule, thus achieving the unprecedent ethane adsorption capacity (62.6cm3 g-1) and ethane/ethylene uptake ratio (3.34) under low-pressure region (0.1 bar and 298 K). The ethane-induced structural transition behavior is uncovered by a collaboration of single-crystal X-ray diffraction, in-situ variable pressure X-ray diffraction and theoretical calculations, elucidating the synergetic mechanism of cross-section matching and multiple supramolecular interactions within the tailor-made pore channels. Dynamic breakthrough experiments revealed the outstanding separation performance of Zn(ad)(min) in the production of ultra-high purity ethylene (> 99.995%) with a productivity of up to 39.2 L/kg under ambient conditions.

Flexible Array of Rigid Porous Microneedles for Bioelectric Skin Patch

Electrodermal patches that generate transdermal currents have been widely investigated for wound healing, anti-perspiration, and drug delivery. Our laboratory has recently developed a metal-free, disposable, fully organic, flexible electrodermal patch with potential for a wide range of healthcare applications. The patch has attracted considerable attention because of its ease of use, lack of need for an external power source, improved drug penetration, and, above all, its simplicity. By selecting soft materials for the patch and electrodes, a total thickness of less than 2 mm has been achieved, and the patch remains flexible enough to be used on skin surfaces and other surfaces. However, the application is limited at the present stage due to the high resistance of the stratum corneum of the outer skin layer in addition to the lower output of the on-board enzyme batteries.Microneedle array can be an attractive solution as it can penetrate through the stratum corneum without reaching blood vessels or nerves. Especially, solid porous microneedles (PMNs), which have microscopic channels throughout the needle structure, exhibit characteristic solution permeability. This serves as a pathway for transdermal iontophoresis drug delivery. Furthermore, modification of the connecting pores with electrically charged materials can generate electroosmotic flow (EOF) inside PMNs, which can enhance drug penetration into the skin without charge or size limitations. Most of the reported microneedle-based skin devices used a hard substrate with high mechanical strength as the base. However, when devices are used on sited of high curvature and deformation, contact with the skin surface is likely to be uneven. This can lead to reduced medical effectiveness, pain, and device breakage. Here, we developed a flexible microneedle array, which provides a stable skin-application effect, by combining a needle portion made of rigid material and a substrate portion made of flexible material.The flexible PMN array was fabricated by integrating rigid PMNs onto the flexible substrate such as polydimethylsiloxane (PDMS) or polyurethane (PU) sheets. The needle part was fabricated by photopolymerizing a mixture of glycidyl methacrylate, trimethylolpropane trimethacrylate and triethylene glycol dimethacrylate, together with a mixture of polyethylene glycol (PEG) and diethylene glycol monomethyl ether (DEG) as porogen. The porogen was dissolved after photopolymerization to form submicron channels networks inside the PMNs. The PMNs were integrated with flexible substrates by solidifying together directly for mechanical fixation. We then evaluated the developed flexible PMN array as follows. First, it was confirmed that the transcutaneous resistance was reduced by applying the flexible PMN patch, both on the flat and curved pig skins. Second, in combination with a bio battery consisting of an enzyme-modified fabric electrode, it was demonstrated that a stable transcutaneous current was generated from glucose and enzyme even on the curved surfaces. In addition, ex vivo experiments showed skin penetration performance while maintaining flexibility.In summary, we developed a method to fabricate rigid PMNs directly bond onto the flexible substrates. We then confirmed that the flexible PMN array can conformably fit on and penetrate curved pig skins. Such flexible and disposable skin patches combined with rigid PMNs can serve as a platform for a wide range of medical, healthcare, and cosmetic applications. Figure 1

Vapor–liquid equilibria (VLE), density, and viscosity of the ternary mixtures of ethane, water, and bitumen at T = 190–210 °C and P = 2.5 MPa—Measurements and CPA-EoS modeling

In this paper, we study vapor-liquid equilibria (VLE) of a ternary system consisting of ethane, water and Mackay River bitumen. The experimental measurements were compared with the predictions of the Cubic Plus Association (CPA) Equation of State (EoS) model at temperatures ranging from 190 to 210 °C and at 2.5 MPa pressure. The feed mole fractions of ethane and water are varied while maintaining a constant bitumen mole fraction to study the VLE region and the associated thermophysical properties, such as the density and viscosity, of the liquid phase. The ternary phase diagrams are constructed at three different temperatures (190, 200, and 210 °C) and pressure at 2.5 MPa. Liquid (L), liquid–liquid (LL), vapor–liquid (VL), and vapor–liquid–liquid (VLL) phase boundaries are determined using phase stability analysis and flash calculations. The experimentally determined phase molar compositions are reported for ethane, water, and bitumen and compared with the model predictions. The AARDs for predicting the liquid phase composition for bitumen, water, and ethane are 1.71 %, 9.34 %, and 3.16 %, respectively. For the vapor phase composition, the AARDs for the water and ethane are 5.91 % and 4.75 %, respectively.

Visible-Light-Induced Three-Component Reactions of α-Diazoesters, Indazoles and Cyclic Ethers

An efficient method was developed for construction of N-short-chain ether attached carbonyl group-substituted indazoles. The visible-light-induced three-component reactions of α-diazoesters, indazoles and cyclic ethers, under extremely mild conditions, led to the corresponding mixture of N1 and N2 short-chain ether substituted indazoles in good to excellent yields.

Simultaneous extraction and quantification of hydrophilic and lipophilic antioxidants in Solanum lycopersicum L. varieties marketed in Saudi Arabia

Abstract Several varieties of Solanum lycopersicum L. are consumed in Saudi Arabia, including the most expensive Ramis tomato, which is claimed to be rich in antioxidants. However, there is a lack of studies on the extraction and quantification of antioxidants in tomatoes marketed in Saudi Arabia. Therefore, this study aimed to develop a straightforward method to extract and quantify phenolics and carotenoids in tomatoes consumed in Saudi Arabia. The developed method used glass coverslips for homogenisation and a methanol-petroleum ether mixture for extraction. In 15 investigated varieties, antioxidants were abundantly present in the skin part (2.0 ± 0.72 mg/g of phenolics and 229.50 ± 21.10 μg/g of carotenoids) compared to the pulp (0.67 ± 0.20 mg/g of phenolics and 107.70 ± 21.10 μg/g of carotenoids). Generally, the Saudi varieties contained higher amounts of antioxidants than the imported varieties. The antioxidant content of the Ramis cultivar depends on the cultivation location. For instance, Ramis Awjam shows high amounts of phenolics (2.72 mg/g in the skin extract and 0.63 mg/g in the pulp) and carotenoids (338.04–388.41 μg/g in the skin and 173.93–205.75 μg/g in the pulp). This study provides valuable insights that can assist in selecting the cultivar and location of tomatoes with the maximum antioxidant quantities.

Stage-wise kinetic analysis of ammonia addition effects on two-stage ignition in dimethyl ether

Abstract Ammonia (NH3) has gained considerable attention as a promising carbon-free hydrogen carrier fuel for internal combustion engines, but its direct use in compression-ignition engines presents challenges, often requiring high-reactivity fuels to ignite the premixed NH3/air mixture and initiate combustion. This study focuses on the ignition process of binary NH3 and dimethyl ether (DME) mixtures, as DME is a carbon-neutral, high-reactivity fuel. A key novelty of this paper is the comparison of the ignition processes of DME and NH3/DME mixtures from a temporal, process-oriented perspective, analyzing chemical kinetics across distinct ignition phases rather than focusing solely on instantaneous reactions at discrete time points. The stage-wise analysis reveals that NH3 has minimal impact on the control mechanism governing the two-stage ignition process of DME. Specifically, DME still largely depends on OH radical proliferation during low-temperature oxidation (LTO), which releases heat as the reaction progresses. As the temperature increases, LTO branching pathways gradually shift to chain-propagation pathways, reducing overall reaction activity. The reactivity and temperature rise rate of the system are then governed by the H2O2 loop mechanism before thermal ignition. However, ammonia significantly extends the ignition delay of DME by competing with OH radicals, which are critical for DME oxidation, thus inhibiting ignition. As the ignition reaction proceeds, ammonia kinetics become more involved. For example, nitrogen-containing species from NH3 oxidation, such as NO, NO2, and NH2, react with CH3OCH2 to form CH3OCHO, reducing the flux through the LTO pathway of DME. While ammonia reaction pathways also produce OH radicals, this occurs at the expense of HO2 and H radicals, leading to H2O2 formation. Overall, these findings demonstrate the substantial impact of ammonia addition on DME ignition, highlighting the need for further research to better understand NH3/DME binary fuel ignition and to optimize the design and operation of NH3/DME dual-fuel engines for improved efficiency and reliability.

Experimental results on a chiller using a CO2-DME mixture

CO2-DME (Carbon Dioxide-Dimethyl Ether) mixtures raised our interest in the last year as they promise to increase the COP with respect to pure CO2 while maintaining GWP = 1. The mixture can be non-flammable, as far as the percentage of DME is low. This study presents experimental findings obtained from a chiller system utilizing CO2-DME mixtures as the working fluid. The experimental investigation aims to analyse the performance and behaviour of the chiller under varying operating conditions. Key parameters, such as coefficient of performance, cooling capacity, and thermodynamic behaviour are examined to assess the suitability and efficacy of the CO2-DME mixture in chiller applications. The experimental results shed light on the thermodynamic characteristics and operational considerations of the chiller system, providing valuable insights into the potential of CO2-DME mixtures for environmentally friendly, safe and energy-efficient cooling technologies. The experimental findings indicate a maximum increase in COP of 15 % for a mixture comprising 10 % DME, with a condensation temperature of 35 °C. Furthermore, the cooling capacity is reduced only by 7 % in the worst case.

Composition and Activities of Carpesium macrocephalum Franch. & Sav. Essential Oils

Carpesium macrocephalum, a species native to China, Korea, Japan, and Russia, has been used medicinally in the countries of its origin. Though mono- and sesquiterpenoids are known constituents of C. macrocephalum, the complete analysis of essential oils produced by the roots and aerial parts of the plant has not been published until now. The present study discloses considerable differences in the composition and cytotoxic activity of essential oils distilled from roots and shoots of C. macrocephalum. The GC-MS-FID analyses have led to the identification of 131 compounds in all, of which 114 were found in aerial parts and 110 in the roots of the plants. The essential oil distilled from shoots contained a mixture of nerol and thymol methyl ether (c. 26%), neryl isobutyrate (c. 12%) and linalool (c. 9%) as major constituents, whereas alantolactone (c. 29%), thymol methyl ether (c. 7%) and 2,5-dimethoxy-p-cymene (thymohydroquinone dimethyl ether, c. 7%) predominated in the essential oil obtained from the roots. The oils demonstrated weak antibacterial activity against Staphylococcus aureus and, at concentrations up to 2.08 mg/mL (oil from the aerial parts) and up to 3.38 mg/mL (oil from roots), were inactive against Gram-negative bacteria. The essential oil from the roots of the plant demonstrated strong but not selective cytotoxic activity.

Synthesis and characterization of a novel eight-membered cyclo-1,3,3,5,7,7-hexaphenyl-1,5-dibora-3,7-disiloxane and 4,4ˈ-bipyridine, 1D adduct

Simple adducts of cyclo-diboradisiloxanes (Lewis acid) and amines (Lewis base) have been reported in the literature. However, the method for the synthesis of an 8-membered cyclo-diboratetrasiloxane, as well as its adducts, was modified in this report to save cost and achieve new results. In the literature, the synthesis of cyclo-1,3,3,5,7,7-hexaphenyl-1,5-dibora-3,7-disiloxane (Ph6B2Si2O4) (3) has been reported using diphenylsilanediol and phenylboronic acid and a Dean-Stark apparatus for the removal of water. However, in this study, molecular sieves were used for the facile removal of water, and the crude product recrystallized from diethyl ether and petroleum ether (3:1 ratio) to give compound 3. Compound 3 was reacted with 4,4’-bipyridine in a mixture of diethyl ether and petroleum ether solvents at reflux to give a 1D polymer [Ph6B2Si2O4]·L1 (4). Furthermore, compound 4 was characterized with various characterization methods such as single-crystal XRD, nuclear magnetic resonance, and FT-IR spectroscopy. The single crystal X-ray diffraction studies shows that the title compound crystalizes in the triclinic crystal system in the centrosymmetric space group P-1, a = 10.9372(4) Å, b = 18.4221(6) Å, c = 19.4697(6) Å, α = 70.533(3)°, β = 86.476(3)°, γ = 88.517(3)°, V = 3691.6(2) Å3, Z = 2, T = 173.0 K, μ(MoKα) = 0.122 mm-1, Dcalc = 1.204 g/cm3, 21463 reflections measured (5.196° ≤ 2Θ ≤ 56.45°), 14525 unique (Rint = 0.0185, Rsigma = 0.0483) which were used in all calculations, the final R1 was 0.0721 (I > 2σ(I)) and wR2 was 0.2143 (all data) with the 8-membered cyclo-1,3,3,5,7,7-hexaphenyl-1,5-dibora-3,7-disiloxane (Ph6B2Si2O4) (3) configuration.

Nickel-Catalyzed C-C Activation of Vinylcyclobutane with Visible Light: Scope, Mechanism, and Application to Chemically Recyclable Polyolefins.

N-heterocyclic carbene (NHC)-supported nickel complexes were investigated for the oxidative ring-opening of vinylcyclobutane (VCB) and photocatalytic activity. Addition of VCB to in situ generated [(NHC)Ni(0)] compounds furnished (NHC)Ni(VCB)2 that underwent oxidative addition and conversion to the corresponding Ni(II) alkyl, allyl-metallacycles. The (NHC)Ni(C6H10) metallacycles were isolated, characterized, and exhibited high thermal and chemical stability. Irradiation with visible light at ambient temperature produced a mixture of ethylene and 4-vinylcyclohexene and 1,5-cyclooctadiene, cycloaddition dimers of butadiene, arising from formal retro-[2 + 2] cycloaddition. A mixture of hexadiene products arising from β-H elimination from the metallacycle was also observed. Free ethylene also underwent a secondary reaction to form cyclopropane products through formal [2 + 1] cycloaddition. A series of sterically and electronically modified NHC ligands was evaluated to establish the structure-activity relationship governing the rate of photocatalytic conversion of VCB and the resulting product distribution. Isotopic labeling experiments, resting state analysis, and independent synthesis of a range of nickel bis(olefin) complexes provided insight into the mechanism of the reaction and origins of the organic product mixture. (NHC)Ni-catalysis was also applied toward the retro-[2 + 2] depolymerization of (1,n'-divinyl)-oligocyclobutane to butadiene dimers.

Turbulent pipe flow and heat transfer of a binary mixture at supercritical pressure: Influences of cross-diffusion effects

Cross-diffusion effects, including Soret and Dufour effects, are enhanced around the pseudo-critical temperature (Tpc) of a binary mixture. Their influences on heat transfer at supercritical pressure have been scarcely studied. To bridge this gap, large-eddy simulations (LES) are conducted to investigate forced convective heat transfer of a CO2–ethane mixture at supercritical pressures in a circular pipe subject to a uniform heat flux. Both heating and cooling conditions, along with varying initial concentrations and thermodynamic pressures, are included in the simulations. The LES results reveal that the Soret effect causes concentration separation, resulting in a concentration boundary layer. The magnitudes of the thermodiffusion factor (kT) and the radial temperature gradient control the intensity of separation, which is more pronounced at near-critical pressure and high heat flux. Since kT is significant only around Tpc, downstream decay of the concentration separation is observed as the loci of T=Tpc migrate away from the wall so that the local radial temperature gradient diminishes. The primary factors affecting heat transfer are the variations in thermal conductivity and isobaric specific heat resulting from concentration separation. In contrast, the Dufour effect and the accompanying inter-diffusion play negligible roles. In deterioration scenarios, the bulk Nusselt number (Nub) shows a maximum relative drop of 8%, whereas in enhancement scenarios, Nub shows a maximum relative increase in 10%, with both deterioration and enhancement decaying downstream. Cross-diffusion effects have negligible impacts on density and streamwise velocity, but noticeably alter streamwise velocity fluctuation and turbulent kinetic energy.