Acetylene Molecules Research Articles

Radicals in Annulation of Mixed Benzoyl Phosphonium‐Iodonium Ylide and Acetylenes Explored by EPR‐ST Spectroscopy

AbstractAnnulation of mixed phosponium‐iodonium ylides and compounds with a triple bond is an interesting example of the synthesis of different types of heterocycles in one‐pot, metal‐free systems at ambient temperature to give substituted oxazoles in the reaction with nitriles and phosphorus‐containing λ5‐phosphinolines and substituted furans in the reaction with acetylenes. The iodonium group in the mixed ylides provides the possibility for the radical initiation of the reaction. Herein, we investigated the generation of primary radicals and the formation of phosphorus‐containing products in the photolysis of benzoyl phosphonium‐iodonium ylide alone and in its reaction with acetylenes in DCM by EPR and 31P NMR spectroscopies with the use of two most popular spin traps, PBN and DMPO. The results allowed us to account the crucial difference in the registered radicals in the two systems for the aggregation of the components, with ylide molecules forming a core and acetylene molecules being a shell of the aggregates in DCM, in which the annulation occurs. The peculiarities of the reactions of PBN and DMPO with generated radicals are discussed.

Cavity ring-down spectroscopy of acetylene near [formula omitted]

A continuous-wave cavity ring-down spectrometer was employed to record the spectrum of the acetylene molecule spanning the 12350 - 12790 cm−1 region. A total of 747 lines from the principal isotopologue and 68 lines from 12C13CH2 were identified, with nearly all line intensities retrieved from the spectra. These lines belong to eighteen vibrational bands of 12C2H2 and two vibrational bands of 12C13CH2, among which five vibrational bands are reported here for the first time. Spectroscopic constants were deduced for all the identified bands, and the vibrational dipole moment squared along with Herman–Wallis coefficients were determined for the majority of these bands. Additionally, several resonance interactions were thoroughly explored.

Base-Promoted Annulated Aromatization of Aryl Acetylenes with Dimethyl Sulfoxide to Access Symmetrical/Unsymmetric m-Terphenyl.

A protocol for selective and efficient synthesis of symmetrical and unsymmetrical m-terphenyls is presented among aryl acetylene and DMSO in the presence of KOH and methanol. In this reaction, two molecules of aryl acetylene contribute four carbons, and DMSO, as a dual carbon donor, provides two carbons to a new aromatic ring. This protocol can be tolerated for the electron-donating or disubstituted phenylacetylenes as well as the heterocyclic acetylene derivatives.

Production of Acetylene from Viable Feedstock: Promising Recent Approaches.

The potential of acetylene is extremely high both in chemical industry and synthetic applications due to unsaturated nature and the smallest active C≡C unit. The production of many essential necessities is originated from acetylene; however, the formation of acetylene molecule requires a lot of energy. Currently, the access to acetylene is based on coal processing, methane reforming and calcium carbide hydrolysis. Recently, extensive research has been done to decrease the cost of acetylene. In this review, the routes to acetylene were highlighted, considering the energy consumption in kW ⋅ h/t of the product to evaluate the best approach. Since energy prices depend on various regions, the cost of the product is complicated. The manufacturing of acetylene is usually accompanied by formation of by-products, which may be valuable or not. The review should help to identify current status and not overlook promising approaches.

Transition Metal-Catalyzed Dual C-H Activation/Annulation Reactions Involving Internal Alkynes.

Recently, transition metal-catalyzed ortho-C-H bond activation/annulations involving two internal alkyne molecules have been extensively used to synthesize highly substituted polycyclic aromatic scaffolds. Such reactions have emerged as a powerful atom and step-economical strategy for the assembly of multifunctional bioactive molecules. In this context, we focused on the recent achievements of dual C-H bond activation/annulations, as well as functionalization reactions involving diaryl/alkyl alkynes.

21.8 W acetylene-filled hollow-core anti-resonant fiberamplified spontaneous emission source at 3.1 µm.

We report a 20-W-level acetylene-filled nested hollow-core anti-resonant fiber (nested HC-ARF) amplified spontaneous emission (ASE) source at 3.1 µm. A 1535 nm hundred-watt wavelength tunable single-frequency fiber laser with a high signal-to-noise ratio and narrow linewidth is built for pumping acetylene molecules. Simultaneously, a homemade 120 µm core diameter eight-tube nested HC-ARF is used as a gas chamber to obtain high pump laser coupling efficiency. The mid-infrared (mid-IR) ASE source output power of 21.8 W is achieved at 3.1 µm through the low-pressure acetylene gas-filled nested HC-ARF, and the slope efficiency is 25.1%. In addition, the ASE source features an excellent beam quality of Mx 2 = 1.16 and My 2 = 1.13. To the best of our knowledge, for the first time, it is a record output power for such mid-infrared ASE sources while maintaining excellent beam quality. This work provides a new way to achieve high-power mid-infrared emission.

Understanding the Impact of Group 14 Elements on the Reactivity of [1 + 2] Cycloaddition Reaction between a Cyclic (Alkyl)(amino)carbene Analogue with a Group 14 Element and a Heavy Acetylene Molecule.

Computational exploration using the density functional theory framework (M06-2X-D3/def2-TZVP) was undertaken to investigate the [1 + 2] cycloaddition reaction between a five-membered-ring heterocyclic carbene analogue (G14-Rea; G14 = group 14 element) and a heavy acetylene molecule (G14G14-Rea). It was theoretically observed that exclusively Si-Rea, Ge-Rea, and Sn-Rea demonstrate the capacity to participate in the [1 + 2] cycloaddition reaction with the triply bonded SiSi-Rea. In addition, only three heavy acetylenes (SiSi-Rea, GeGe-Rea, and SnSn-Rea) can catalyze the [1 + 2] cycloaddition reaction with Si-Rea. Our theoretical findings elucidated that the reactivity trend observed in these [1 + 2] cycloaddition reactions primarily arise from the deformation energies of the distorted G14G14-Rea. Also, our study reveals that the bonding characteristics of their respective transition states are controlled by the singlet-singlet interaction (donor-acceptor interaction), rather than the triplet-triplet interaction (electron-sharing interaction). Additionally, our work demonstrates that the bonding behavior between G14-Rea and G14G14-Rea is predominantly determined by the filled p-π orbital of G14G14-Rea (HOMO) → the empty perpendicular p-π orbital of G14-Rea (LUMO), rather than the vacant p-π* orbital of G14G14-Rea (LUMO) ← the filled sp2 orbital of G14-Rea (HOMO).

Copper catalyzed cycloaddition for the synthesis of non isomerisable 2′ and 3′-regioisomers of arg-tRNAarg

In this report, non-isomerisable analogs of arginine tRNA (Arg-triazole-tRNA) have been synthesized as tools to study tRNA-dependent aminoacyl-transferases. The synthesis involves the incorporation of 1,4 substituted-1,2,3 triazole ring to mimic the ester bond that connects the amino acid to the terminal adenosine in the natural substrate. The synthetic procedure includes (i) a coupling between 2′- or 3′-azido-adenosine derivatives and a cytidine phosphoramidite to access dinucleotide molecules, (ii) Cu-catalyzed cycloaddition reactions between 2′- or 3′-azido dinucleotide in the presence of an alkyne molecule mimicking the arginine, providing the corresponding Arg-triazole-dinucleotides, (iii) enzymatic phosphorylation of the 5′-end extremity of the Arg-triazole-dinucleotides with a polynucleotide kinase, and (iv) enzymatic ligation of the 5′-phosphorylated dinucleotides with a 23-nt RNA micro helix that mimics the acceptor arm of arg-tRNA or with a full tRNAarg. Characterization of nucleoside and nucleotide compounds involved MS spectrometry, 1H, 13C and 31P NMR analysis. This strategy allows to obtain the pair of the two stable regioisomers of arg-tRNA analogs (2′ and 3′) which are instrumental to explore the regiospecificity of arginyl transferases enzyme. In our study, a first binding assay of the arg-tRNA micro helix with the Arginyl-tRNA-protein transferase 1 (ATE1) was performed by gel shift assays.

Construction of an extraordinary stable mesoporous carbocatalyst in acetylene hydrochlorination via boric acid assistance

In recent years, metal-free carbon catalysts have garnered significant attention as substitutes for metal catalysts due to their cost-effectiveness and increased resistance to poisoning. However, the stability of metal-free carbon catalysts still lags behind that of metal catalysts, presenting a significant hurdle to industrialization. To enhance the catalytic stability of these catalysts, a boron-nitrogen co-doped mesoporous carbon (B, N-MC) catalyst was synthesized using polyacrylonitrile (PAN) as the carbon and nitrogen source, with boric acid serving as the electron regulator. The acetylene conversion on the B, N-MC(0.5) catalyst reached 62.8 % at 220 °C and gas hourly space velocity (GHSV) of C2H2 at 300 h−1, even high than 0.25%Au/AC catalyst (53.3 %). Importantly, the B, N-MC(0.5) catalyst exhibited excellent stability, maintaining its initial activity even after 500 h of evaluation. Experimental and theoretical analyses demonstrate that the B–N pairs, facilitated by the electronic regulation ability of boric acid, effectively inhibits the polymerization of acetylene molecules, mitigates the formation of carbon deposits, thereby enhancing the stability of the catalyst.

Extending carbon chemistry at high-pressure by synthesis of CaC2 and Ca3C7 with deprotonated polyacene- and para-poly(indenoindene)-like nanoribbons

Metal carbides are known to contain small carbon units similar to those found in the molecules of methane, acetylene, and allene. However, for numerous binary systems ab initio calculations predict the formation of unusual metal carbides with exotic polycarbon units, [C6] rings, and graphitic carbon sheets at high pressure (HP). Here we report the synthesis and structural characterization of a HP-CaC2 polymorph and a Ca3C7 compound featuring deprotonated polyacene-like and para-poly(indenoindene)-like nanoribbons, respectively. We also demonstrate that carbides with infinite chains of fused [C6] rings can exist even at conditions of deep planetary interiors ( ~ 140 GPa and ~3300 K). Hydrolysis of high-pressure carbides may provide a possible abiotic route to polycyclic aromatic hydrocarbons in Universe.

Novel alkyne chromophore of the isophorone derivatives: synthesis, electrochemical evaluation, DFT, and processable bottom contact/top-gate OFET applications

Fused alkyne molecules are important in organic semiconductors due to their desirable properties. Here, we report the design and synthesis of a new series of A–π–D molecules (III–VII) that can serve as mild electron acceptors to generate wide-bandgap p-type small compounds for use in organic field-effect transistors. The incorporation of donor units into fused isophorone frameworks can be used to tune the frontier molecular orbital energies. The electrochemical, optical, and thermal properties of the compounds were characterized. Compound VI, which has a fused phenyl-substituted alkyne moiety, had the highest occupied molecular orbital energy level as determined by optical and electrochemical analysis. Density functional theory calculations revealed that compounds VI and III had lower hole reorganization energy (λh) than the corresponding isophorone extended conjugated-based compounds (I–II). Conversely, compounds I and II had lower electron reorganization energy (λe) than the corresponding fused alkyne compounds. This is in line with the observed adiabatic ionization potential and electron affinity values. Consequently, devices fabricated with compound VI exhibited high mobility and low threshold voltage.

Development of a universal method for vibrational analysis of the terminal alkyne C≡C stretch.

The terminal alkyne C≡C stretch has a large Raman scattering cross section in the "silent" region for biomolecules. This has led to many Raman tag and probe studies using this moiety to study biomolecular systems. A computational investigation of these systems is vital to aid in the interpretation of these results. In this work, we develop a method for computing terminal alkyne vibrational frequencies and isotropic transition polarizabilities that can easily and accurately be applied to any terminal alkyne molecule. We apply the discrete variable representation method to a localized version of the C≡C stretch normal mode. The errors of (1) vibrational localization to the terminal alkyne moiety, (2) anharmonic normal mode isolation, and (3) discretization of the Born-Oppenheimer potential energy surface are quantified and found to be generally small and cancel each other. This results in a method with low error compared to other anharmonic vibrational methods like second-order vibrational perturbation theory and to experiments. Several density functionals are tested using the method, and TPSS-D3, an inexpensive nonempirical density functional with dispersion corrections, is found to perform surprisingly well. Diffuse basis functions are found to be important for the accuracy of computed frequencies. Finally, the computation of vibrational properties like isotropic transition polarizabilities and the universality of the localized normal mode for terminal alkynes are demonstrated.

Probing Photoionization Dynamics in Acetylene with Angle-Resolved Attosecond Interferometry.

Photoionization of acetylene by extreme ultraviolet light results in a stand-alone contribution from the outermost valence orbital, followed by well-separated photoelectron bands from deeper molecular orbitals. This makes acetylene an ideal candidate for probing the photoionization dynamics in polyatomic molecules free from the spectral congestion often arising after interaction with an attosecond pulse train. Here, using an angle-resolved attosecond interferometric technique, we extract the photoionization time delays for the outermost valence orbital in acetylene relative to an atomic target, namely argon. Compared to argon, the photoemission from the acetylene molecule is found to be advanced by almost 28 attoseconds. The strong variation of the relative photoionization time delays as a function of the photoemission angle was interpreted using an analytical model based on semiclassical approximations to be the interplay between different short-range potentials along and perpendicular to the molecular axis. Our results highlight the importance of using attosecond time-resolved measurements to probe the nonspherical nature of the molecular potential, even in the case of relatively small, linear systems.

Low-energy positron scattering by small hydrocarbons: methane, acetylene, ethylene, and ethane molecules

Low-energy positron scattering by small hydrocarbons: methane, acetylene, ethylene, and ethane molecules

Possible Roles of Transition Metal Cations in the Formation of Interstellar Benzene via Catalytic Acetylene Cyclotrimerization.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous interstellar molecules. However, the formation mechanisms of PAHs and even the simplest cyclic aromatic hydrocarbon, benzene, are not yet fully understood. Recently, we reported the statistical and dynamical properties in the reaction mechanism of Fe+-catalyzed acetylene cyclotrimerization, whereby three acetylene molecules are directly converted to benzene. In this study, we extended our previous work and explored the possible role of the complex of other 3d transition metal cations, TM+ (TM = Sc, Ti, Mn, Co, and Ni), as a catalyst in acetylene cyclotrimerization. Potential energy profiles for bare TM+-catalyst (TM = Sc and Ti), for TM+NC--catalyst (TM = Sc, Ti, Mn, Co, and Ni), and for TM+-(H2O)8-catalyst (TM = Sc and Ti) systems were obtained using quantum chemistry calculations, including the density functional theory levels. The calculation results show that the scandium and titanium cations act as efficient catalysts in acetylene cyclotrimerization and that reactants, which contain an isolated acetylene and (C2H2)2 bound to a bare (ligated) TM cation (TM = Sc and Ti), can be converted into a benzene-metal-cation product complex without an entrance barrier. We found that the number of electrons in the 3d orbitals of the transition metal cation significantly contributes to the catalytic efficiency in the acetylene cyclotrimerization process. On-the-fly Born-Oppenheimer molecular dynamics (BOMD) simulations of the Ti+-NC- and Ti+-(H2O)8 complexes were also performed to comprehensively understand the nuclear dynamics of the reactions. The computational results suggest that interstellar benzene can be produced via acetylene cyclotrimerization reactions catalyzed by transition metal cation complexes.

Isolation and spectroscopy of C2H+ ions in helium droplets

Ethynylium (C2H+) may be an important intermediate in astrochemistrybut remains poorly studied by laboratory techniques due to its high reactivity. Immersion of single acetylene molecules in helium nanodroplets followed by electron impact ionization effectively generates and isolates C2H+ cations in an inert cryogenic environment, enabling infrared spectroscopic measurements. We find that in the C-H stretching range, the C2H+ spectrum appears as a triplet with splitting of 33.6 cm−1 and 37.5 cm−1. The splitting is temporarily assigned to the product of interactions between the C-H stretching mode and overtones of the bending mode.

Titania-supported Cu Single Atom Catalyst for Electrochemical Reduction of Acetylene to Ethylene at Low-Concentrations with Suppressed Hydrogen Evolution.

Electrochemical acetylene reduction (EAR) is a promising strategy for removing acetylene from ethylene-rich gas streams. However, suppressing the undesirable hydrogen evolution is vital for practical applications in acetylene-insufficient conditions. Herein, weimmobilized Cu single atoms on anatase TiO2 nanoplates (Cu-SA/TiO2 ) for electrochemical acetylene reduction, achieving an ethylene selectivity of ∼97% with a 5vol.% acetylene gas feed (Ar balance). At the optimal Cu single atom loading, Cu-SA/TiO2 wasable to effectively suppress HER and ethylene over-hydrogenation even when using dilute acetylene (0.5vol.%) or ethylene-rich gas feeds, delivering a 99.8% acetylene conversion, providing a turnover frequency of 8.9 × 10-2 s-1 , which is superior to other EAR catalysts reported to date. Theoretical calculations showed that the Cu single atoms and the TiO2 support acted cooperatively to promote charge transfer to adsorbed acetylene molecules, whilst also inhibiting hydrogen generation in alkali environments, thus allowing selective ethylene production with negligible hydrogen evolution at low acetylene concentrations. This article is protected by copyright. All rights reserved.

Mechanistic insight into acetylene hydrochlorination with Ru-ligands via dual activation promoted by metal-ligands cooperative catalysis

Ru-based catalysts have shown great potential for the environmentally friendly industrialization of acetylene hydrochlorination. However, the high cost and reduction of active sites in Ru catalysts have limited their practical applications. In this study, we propose a strategy to optimize the electronic structure of Ru single-atom catalysts by leveraging the strong coordination ability of ligands with the metal and apply this strategy to acetylene hydrochlorination. The experimental results verify that the performance of the catalyst increases with the increase of the ligand. Characterization results indicate that ligands not only optimize the electronic properties of Ru single atoms by forming a RuCl2-N structure, but also enhance the adsorption of reactants on the catalysts. DFT calculations reveal that the ligand-modified Ru species can efficiently adsorb and activate acetylene molecules, while the adjacent excessive ligand can adsorb and dissociate HCl molecules. This ultimately leads to an addition reaction between acetylene and HCl through a hydrogen overflow mechanism.

Microwave Spectrum and Novel Molecular Structure of (Z)-1-Chloro-3,3,3-trifluoropropene-Acetylene.

The gas-phase heterodimer formed between (Z)-1-chloro-3,3,3-trifluoropropene and acetylene is investigated using quantum chemistry calculations and observed via chirped-pulse Fourier transform microwave (FTMW) spectroscopy. Subsequent analysis of higher resolution spectra, including those using a sample enriched in H13C13CH, obtained with a Balle-Flygare FTMW spectrometer reveals a novel structure, as predicted by theory, for the complex, in which the acetylene functions as the gas-phase (Lewis) base and the halopropene as the acid. In the equilibrium structure, the acetylene molecule is located perpendicular to the symmetry plane of (Z)-1-chloro-3,3,3-trifluoropropene with the triple bond interacting with the two olefinic hydrogens. Mapped electrostatic potential surfaces suggest that this structure results from a reduction in the nucleophilicity of the halogen atoms as compared to previously studied acetylene halo-olefin complexes and a concomitant increase in the electrophilicity of the hydrogen atoms.

Effective separation of acetylene from carbon dioxide via commensurate adsorption in a microporous metal-organic framework

Separating acetylene and carbon dioxide is a significant challenge due to their similar physicochemical properties. Herein, we reported an ultramicroporous metal–organic framework, PCN-200, which possesses narrow zig-zag one-dimensional channels with a size of about 4.5 Å. The pore surface of PCN-200 features numerous uncoordinated oxygen polar sites that are symmetrically distributed, facilitating the strong and commensurate binding of acetylene molecules (57.0 kJ mol−1). At 298 K and 1 bar, PCN-200 demonstrates a high selectivity (6.4) towards acetylene over carbon dioxide, and this separation performance is validated through dynamic breakthrough experiments. Simulation studies were conducted to gain insight into the adsorption mechanism for acetylene and carbon dioxide molecules in PCN-200.