Hydrogen evolution reactions (HER) are crucial for producing renewable and ecological hydrogen energy. Here we report the finding that ethyl acetylene (C2H2), borane (B2H6), and benzene (C6H6) undergo drastic dehydrogenation reactions upon interaction with niobium cluster anions (Nbn-). This finding was enabled by our very sensitive and specialized mass spectrometer, which monitored the cluster ions and the resulting metal carbide and boride products in real time. Through mass spectrometry experiments and density functional theory computations, we delved into the varying reactivities of these common gas molecules with small Nbn- clusters and elucidated the underlying reaction mechanisms. These findings shed light on the HER mechanisms of hydrocarbon and hydroboron molecules on superatomic Nbn- clusters, furnishing valuable insights pertinent to the advancement of hydrogen energy resources.

Oxidation study of small hydrocarbons at elevated pressure. Part I: Neat 1,3-butadiene

Mechanism and safety analysis of acetylene decomposition explosion: A combined ReaxFF MD with DFT study

Experimental and kinetic modeling studies of phenyl acetate pyrolysis at atmospheric pressure

Gold catalyzed oxidation of vinyl acetylenes into vinyl & divinyl diketones and its synthetic application

Abstract In the production of chloroprene rubber, acetylene dimerization over the Nieuwland catalyst is an important step. The addition of Mg2+ to the Nieuwland catalyst improves the acetylene conversion and the selectivity toward vinyl acetylene. In this study, active component crystal structure, the role of Mg2+ in the Nieuwland catalyst, the reason for the catalyst deactivation, and the reaction mechanism were analyzed by different characterization techniques. The results indicate that the main reason for the Nieuwland catalyst deactivation is the loss of Cu2+. The addition of Mg2+ will increase the exposure of active sites, reduce the residence time of acetylene in the catalyst, and inhibit the reduction of Cu2+, thereby improving the catalytic performance and stability of the catalyst.

The process of dehydrochlorination of 1,3-dichlorobut-2-ene using caustic potassium in ethylene glycol has been studied, and a technological scheme for the production of vinyl acetylene has been proposed. It is noted that during the process of dehydrochlorination of 1,3-dichlorobut-2-ene, in addition to vinyl acetylene, acetylene homologues are also formed, which are easily separated from commercial vinyl acetylene. Composition and percentage of the formed acetylene homologues has been determined.
 In addition to chloroprene, three more compounds were separated and identified as by-products formed during the dehydrochlorination of 1,3-dichlorobut-2-ene – 3-(chloro-1-[3-chlorobut-2-en-1-yl]oxy)but-2-en, 1-(but-2-yn1-yloxy)-3-chlorobut-2-ene and 1-(but-2-ynyloxy)but-2-yne.

We report the detection for the first time in space of three new pure hydrocarbon cycles in TMC-1: c-C3HCCH (ethynyl cyclopropenylidene), c-C5H6 (cyclopentadiene) and c-C9H8 (indene). We derive a column density of 3.1 × 1011 cm-2 for the former cycle and similar values, in the range (1-2) × 1013 cm-2, for the two latter molecules. This means that cyclopentadiene and indene, in spite of their large size, are exceptionally abundant, only a factor of five less abundant than the ubiquitous cyclic hydrocarbon c-C3H2. The high abundance found for these two hydrocarbon cycles, together with the high abundance previously found for the propargyl radical (CH2CCH) and other hydrocarbons like vinyl and allenyl acetylene (Agúndez et al. 2021; Cernicharo et al. 2021a,b), start to allow us to quantify the abundant content of hydrocarbon rings in cold dark clouds and to identify the intermediate species that are probably behind the in situ bottom-up synthesis of aromatic cycles in these environments. While c-C3HCCH is most likely formed through the reaction between the radical CCH and c-C3H2, the high observed abundances of cyclopentadiene and indene are difficult to explain through currently proposed chemical mechanisms. Further studies are needed to identify how are five- and six-membered rings formed under the cold conditions of clouds like TMC-1.

High-resolution infrared study of vinyl acetylene: The [formula omitted] (214 cm−1) and [formula omitted] (304 cm−1) fundamentals

We present the discovery in TMC-1 of allenyl acetylene, H2CCCHCCH, through the observation of nineteen lines with a signal-to-noise ratio ~4-15. For this species, we derived a rotational temperature of 7±1K and a column density of 1.2±0.2×1013 cm-2. The other well known isomer of this molecule, methyl diacetylene (CH3C4H), has also been observed and we derived a similar rotational temperature, Tr=7.0±0.3 K, and a column density for its two states (A and E) of 6.5±0.3×1012 cm-2. Hence, allenyl acetylene and methyl diacetylene have a similar abundance. Remarkably, their abundances are close to that of vinyl acetylene (CH2CHCCH). We also searched for the other isomer of C5H4, HCCCH2CCH (1.4-Pentadiyne), but only a3σ upper limit of 2.5×1012 cm-2 to the column density can be established. These results have been compared to state-of-the-art chemical models for TMC-1, indicating the important role of these hydrocarbons in its chemistry. The rotational parameters of allenyl acetylene have been improved by fitting the existing laboratory data together with the frequencies of the transitions observed in TMC-1.

We present the discovery in TMC-1 of vinyl acetylene, CH2CHCCH, and the detection, for the first time in a cold dark cloud, of HCCN, HC4N, and CH3CH2CN. A tentative detection of CH3CH2CCH is also reported. The column density of vinyl acetylene is (1.2±0.2)×1013 cm-2, which makes it one of the most abundant closed-shell hydrocarbons detected in TMC-1. Its abundance is only three times lower than that of propylene, CH3CHCH2. The column densities derived for HCCN and HC4N are (4.4±0.4)×1011 cm-2 and (3.7±0.4)×1011 cm-2, respectively. Hence, the HCCN/HC4N abundance ratio is 1.2±0.3. For ethyl cyanide we derive a column density of (1.1 ±0.3)×1011 cm-2. These results are compared with a state-of-the-art chemical model of TMC-1, which is able to account for the observed abundances of these molecules through gas-phase chemical routes.

Mooney viscosity is an essential parameter in quality control during the production of nitrile-butadiene rubber (NBR) by emulsion polymerization. A process model that could help understand the influence of feed compositions on the Mooney viscosity of NBR products is of vital importance for its intelligent manufacture. In this work, a process model comprised of a mechanistic model based on emulsion polymerization kinetics and a data-driven model derived from genetic programming (GP) for Mooney viscosity is developed to correlate the feed compositions (including impurities) and process conditions to Mooney viscosity of NBR products. The feed compositions are inputs of the mechanistic model to generate the number-, weight-averaged molecular weights (Mn, Mw) and branching degree (BRD) of NBR polymers. With these generated data, the GP model is used to output the optimal correlation for the Mooney viscosity of NBR. In a pilot NBR production, Mooney viscosity data of NBR predicted by the process model agree quite well with experimental values. Furthermore, the process model enables the analyses of the univariate and multivariate influence of feed compositions on NBR Mooney viscosity, and the variables include the contents of vinyl acetylene and dimer in 1,3-butadiene, as well as the mass flow rate of the chain transfer agent (CTA) in the process. Based on the results, it is recommended to control the content of vinyl acetylene in the 1,3-butadiene feed below 14 ppm and the content of dimer below 1100 ppm. This developed process model would help stabilize NBR viscosity for a better control of the product quality.

Green Synthesis Of Methyl-6-Amino-5-Cyano-4-Aryl-2,4-Dihydropyrano[2,3-C]Pyrazole-3-Carboxylates using Dimethyl Acetylene dicarboxylate

Abstract The concept of quasistructural molecules is introduced. For quasistructural molecules (a) the notion of a static equilibrium structure, corresponding to a minimum on the potential energy surface of the molecule, loses its strict meaning, (b) internal nuclear motions (rotations and vibrations) become dominant, resulting in an effective molecular structure often even qualitatively different from the equilibrium one, (c) separation of the internal nuclear motions breaks down, rotational and vibrational degrees of freedom cannot be separated from each other when interpreting even the lowest rovibrational eigenstates of the molecule, often resulting in effective rotational constants drastically different from the equilibrium ones even for the ground vibrational eigenstate, (d) classification of the rovibrational states requires the use of permutation‐inversion symmetry and molecular‐symmetry groups, and (e) some of the rovibrational eigenenergies assigned to a vibrational parent state exhibit unconventional (in the most striking cases “negative”) rotational contributions. Molecules showing quasistructural behavior include neutral species, such as dimethyl acetylene, charged species, such as and , van der Waals complexes, such as CH4·H2O, and molecular complexes held together by halogen bonds, like CF3Cl·CH3F.This article is categorized under: Structure and Mechanism > Molecular Structures Theoretical and Physical Chemistry > Spectroscopy Software > Quantum Chemistry

Cover Feature: Reactivity of the Indenyl Radical (C₉H₇) with Acetylene (C₂H₂) and Vinylacetylene (C₄H₄) (ChemPhysChem 11/2019)

Versatile coordination modes of benzothiazole hydrazone derivatives towards Ru(II), Rh(III) and Ir(III) complexes and their reactivity studies with azides and activated alkynes

Conjugated polymers are prominent semiconductors that have unique electric conductivity and photoluminescence. Synthesis of conjugated polymers under high pressure is extremely appealing because it does not require a catalyst or solvent used in conventional chemical methods. Transformation of acetylene and many of its derivatives to conjugated polymers using high pressure has been successfully achieved, but not with dimethyl acetylene (DMA). In this work, we present a high-pressure study on solid DMA using a diamond anvil cell up to 24.4 GPa at room temperature characterized by in situ Fourier transform infrared and Raman spectroscopy. Our results show that solid DMA exists in a phase II crystal structure and is stable up to 12 GPa. Above this pressure, amorphization was initiated and the process was completed at 24.4 GPa. The expected polymeric transformation was not evident upon compression, but only observed upon decompression from a threshold compression pressure (e.g. 14.4 GPa). In situ florescence measurements suggest excimer formation via crystal defects, which induces the chemical reactions. The vibrational spectral analysis suggests the products contain the amorphous poly(DMA) and possibly additional amorphous hydrogenated carbon material.

Equilibrium molecular structures of vinyl carbon chains: Vinyl acetylene, vinyl diacetylene, and vinyl cyanide

Employing triflic anhydride/2-fluoropyridine as an activation system, the coupling reactions of secondary N-aryl amides with terminal alkynes yielded substituted quinolines in moderate to excellent yields. The reaction tolerated both electron-donating and electron-withdrawing groups at the benzamide moiety. Electron-rich aryl acetylenes served as excellent coupling partners, and aliphatic terminal alkynes such as cyclopropyl and conjugate vinyl acetylenes could also be used as reaction partners. By means of 2D NMR techniques (heteronuclear multiple bond correlation (HMBC), heteronuclear single quantum correlation (HSQC)), nitrilium ions were probed as reactive intermediates which are in contrast with that suggested by Movassaghi on the basis of in situ IR monitoring experiments. On the basis of these results, a plausible mechanism for the formation of quinolines was suggested.

DFT investigations on the conversion of acetylene to undesired vinyl acetylene during vinyl acetate synthesis