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In the field of industrial semi‐hydrogenation of trace alkynes amidst alkene feedstocks, the pivotal challenge lies in circumventing the hydrogenation of alkenes. Herein, we present Zr(OH)4 as an innovative catalyst for the semi‐hydrogenation of phenylacetylene, demonstrating remarkable selectivity towards styrene (>96 %), while exhibiting inactivity towards free styrene. Notably, Zr(OH)4 achieves a 95 % conversion of quasi‐industry 1 mol % phenylacetylene within styrene, with a mere 0.44 % styrene loss. Experimental and theoretical results confirm both terminal Zr−O−H and bridge Zr−O−H can dissociate H2, while the terminal Zr−O−H plays a crucial role on activating phenylacetylene through the sequential hydrogenation process of C6H5C≡CH→C6H5C=CH2→C6H5CH=CH2. The high rate of phenylacetylene removal is attributed to its strong adsorption capacity, while Zr(OH)4 has a significantly weaker adsorption capacity for styrene. [ABSTRACT FROM AUTHOR]

An efficient procedure has been proposed for the reaction of molecular iodine with phenylacetylene in the presence of cadmium(II) acetate in DMSO at room temperature, and the reactant ratio has been optimized for the iodination process. Mercuration–demercuration of iodoethynylbenzene with molecular iodine and oxidative homocoupling in the presence of dilithium tetrachlorocuprate have been performed. [ABSTRACT FROM AUTHOR]

The metalation of 1,3-diaryl-4-(arylsulfanyl)imidazolium and 1,3-diaryl-4-(arylsulfonyl)imidazolium chlorides with copper(I) oxide has been studied. The resulting Cu/NHC complexes have been studied as catalysts for the carboxylation of phenylacetylene, benzoxazole, and benzothiazole. The main patterns of this reaction behavior and the dependence of the catalysis efficiency on the NHC structure were revealed. [ABSTRACT FROM AUTHOR]

Phenylacetylene plays a critical role as an intermediate in PAH formation in hydrocarbon flames. In this work, the autoignition characteristics of phenylacetylene were investigated behind reflected shock waves. Ignition delay times were measured at temperatures ranging from 1228 to 1813 K, pressures of 2, 4, and 10 atm, equivalence ratios of 0.5, 1.0, and 2.0, as well as fuel mole fractions of 0.1% and 0.2%. The effects of temperature, pressure, equivalence ratio, and mole fractions on ignition delay time were investigated, and quantitative relationships were obtained by regression analysis of the experimental data. A detailed oxidation mechanism of phenylacetylene based on NUIGMech1.1 was proposed and verified using ignition data. Reaction pathway and sensitivity analyses have been carried out to investigate the significant reaction pathways in the ignition process and key reactions that affect the ignition delay time. The addition reactions by O and OH species contribute significantly to phenylacetylene consumption and promote fuel ignition. Finally, a comparison of the ignition delay times of ethylbenzene, styrene, and phenylacetylene was conducted in this study, and kinetic analyses have been conducted to investigate the impact of different side chains attached to aromatic rings on the ignition of these C8 aromatics. [ABSTRACT FROM AUTHOR]

Understanding the nature of selenium centred hydrogen bond is a growing field of research. Intermolecular C - H · · · Se hydrogen bond has not yet been investigated experimentally in aromatic molecules. The current work aims at understanding the nature and origin of C - H · · · Se hydrogen bond interaction between phenylacetylene ( C 8 H 6 ) and dimethyl selenide ( Se (CH 3) 2 ). The 1:1 complex of [ C 8 H 6 - Se (CH 3) 2 ] is formed in nitrogen matrix at 14 K and probed using infrared spectroscopy. The experimentally obtained infrared spectra have been corroborated with simulated spectra. The nature of the complex has been delineated using Atoms in Molecules (AIM) theory, Natural Bond Orbital (NBO) analysis, and energy decomposition analysis by Symmetry Adapted Perturbation Theory (SAPT). [ABSTRACT FROM AUTHOR]

New nickel-containing catalysts based on the phyllosilicate phase have been obtained by microwave activation for efficient liquid-phase hydrogenation of a number of unsaturated compounds to olefins under relatively mild reaction conditions: T = 100–140°C, pH2 = 1.5 MPa, reaction time 1 h. A comparison of the synthesis methods showed that the best results with 90.1% selectivity of styrene formation at 89.6% conversion of phenylacetylene were obtained on the nickel catalyst prepared by microwave synthesis. [ABSTRACT FROM AUTHOR]

2-(Arylmethyl)benzazoles have been prepared by the sulfur-mediated cyclization of 2-aminophenol or 2-aminoaniline with arylacetylenes in N-methylpiperidine in moderate-to-excellent yields on a gram scale. [ABSTRACT FROM AUTHOR]

Background. Vinyl esters of carboxylic acids are widely used in organic synthesis, in particular in acylation reactions, substrates in asymmetric hydrogenation, cycloaddition, aldol and Mannich reactions, and the synthesis of vinylarenes based on decarboxylation. Vinyl ethers are also used as monomers in polymerization reactions. Their preparation by the action of alkynes on carboxylic acids in the presence of 3d-metal catalysts is promising and requires additional study. Purpose. Synthesis of vinyl esters by the reaction of benzoic, 4-methylbenzoic, 4-bromobenzoic and 2-bromobenzoic acids with phenylacetylene under homogeneous conditions, in the presence of catalytic systems, studying the properties of the synthesis products, carrying out quantum chemical calculations of the process. Methodology. The interaction of substituted benzoic acids, in particular, 4-methylbenzoic acid, 4-bromobenzoic acid and 2-bromobenzoic acid with phenylacetylene, in the presence of catalysts, was used. The methods used were IR, ¹H, 13C NMR and mass spectral analysis. Originality. The synthesis of vinyl esters of benzoic, 4-methylbenzoic, 4-bromobenzoic and 2-bromobenzoic acids with tetrakis-(2-amino-5-ethylthio-1,3,4-thiadiazole) zinc(II) dinitrate ([Zn(C4H7S2)4](NO3)2) including phenylacetylene with the participation of a complex catalytic system. Findings. In the reaction of carboxylic acids with phenylacetylene, a mixture of combination products is formed according to the Markovnikov and Anti-Markovnikov rules. It has been established that the yield of vinyl esters increases in the series 4-CH3-C6H4COOH < C6H5COOH < 4-Br-C6H4COOH < 2-Br-C6H4COOH. The yield of the reaction products of phenylacetylene with carboxylic acids is: 44% (65/35) for 4-methylbenzoic acid, 67% (80/20) for benzoic acid, 78% (82/18) for 4-bromobenzoic acid, 82% (85 /15) for 2-bromobenzoic acid. [ABSTRACT FROM AUTHOR]

Photoredox processes have emerged recently as a powerful tool for methodology developments. In this context, the hydrotrifluoromethylation of alkenes and alkynes using visible light photoredox methodologies has proven its efficiency these last years. This micro-review summarizes the latest developments in this field.

The Pd(II) complexes [Pd(Cp)(L)n]m[BF4]m were synthesized via the reaction of cationic acetylacetonate complexes with cyclopentadiene in the presence of BF3∙OEt2 (n = 2, m = 1: L = PPh3 (1), P(p-Tol)3, tris(ortho-methoxyphenyl)phosphine (TOMPP), tri-2-furylphosphine, tri-2-thienylphosphine; n = 1, m = 1: L = dppf, dppp (2), dppb (3), 1,5-bis(diphenylphosphino)pentane; n = 1, m = 2 or 3: 1,6-bis(diphenylphosphino)hexane). Complexes 1–3 were characterized using X-ray diffractometry. The inspection of the crystal structures of the complexes enabled the recognition of (Cp–)⋯(Ph-group) and (Cp–)⋯(CH2-group) interactions, which are of C–H...π nature. The presence of these interactions was confirmed theoretically via DFT calculations using QTAIM analysis. The intermolecular interactions in the X-ray structures are non-covalent in origin with an estimated energy of 0.3–1.6 kcal/mol. The cationic palladium catalyst precursors with monophosphines were found to be active catalysts for the telomerization of 1,3-butadiene with methanol (TON up to 2.4∙104 mol 1,3-butadiene per mol Pd with chemoselectivity of 82%). Complex [Pd(Cp)(TOMPP)2]BF4 was found to be an efficient catalyst for the polymerization of phenylacetylene (PA) (catalyst activities up to 8.9 × 103 gPA·(molPd·h)−1 were observed) [ABSTRACT FROM AUTHOR]

Trichloro niobium(V) complexes 3 and 4 with the sulfur- or selenium-bridged [OEO]-type bis(phenolate) ligands (E = S, Se) were synthesized and fully characterized on the basis of their NMR spectroscopic data and X-ray crystallographic analysis. In the crystalline state of 4, the [OSeO]-core of the ligand was coordinated to the niobium center in a fac-fashion. The corresponding tribenzyl niobium(V) complexes 5 and 6 were also prepared by the reactions of 3 and 4 with 3 equivalents of PhCH2MgCl in toluene. The X-ray diffraction analysis of 6 revealed that the distorted six-coordinated niobium center incorporated in the [OSeO]-type ligand took a mer-fashion, and one benzyl ligand was coordinated to the niobium center by η2-fashion. Complexes 5 and 6 were tested for the phenylacetylene polymerization that produced poly(phenylacetylene)s (PPAs), oligomers, and triphenylbenzenes (TPBs) depending on the chalcogen atom in the [OEO]-type ligand. [ABSTRACT FROM AUTHOR]

[Display omitted] Acetylacetonate palladium(II) complexes bearing pyridinyl imine ligands [Pd(acac)(L)]BF 4 were synthesized via nitrile displacement in [Pd(acac)(MeCN) 2 ]BF 4 by the bidentate ligands L of type 2-C 5 H 4 N–CH=N–(CH 2) n OMe or 2-C 5 H 4 N–CH=N–Ar. The structures of complexes were analyzed by X-ray diffractometry, NMR, and DFT. The complexes catalyze hydroamination of phenylacetylene with aniline to give the Markovnikov imine product as well as polymerization of norbornene. [ABSTRACT FROM AUTHOR]

The synthesis of quinoline derivatives through bismuth-catalyzed cyclization of phenylacetylene with ethyl 2-(arylimino)acetates has been reported. The excellence of this method is that the reaction is carried out at room temperature, and the catalyst is exceptionally productive, low toxic, and very cheap. The mild reaction conditions added an extraordinary benefit and made it attractive in economic and environmental aspects. The target products were isolated in up to 89% yield. [ABSTRACT FROM AUTHOR]

Helical polymers, a class of organic polymers with a unique spring-like structure, possess interesting electronic configurations and axial quantum transport properties thanks to the tunable interlayer electronic interaction by strain engineering. In this report, we carried out first-principle calculations to investigate the electronic structures and transport properties of the helical polymer with phenylacetylene monomers under compressive strains. The band structures of the material show a remarkable semiconductor-to-metal phase transition and enhanced electronic dispersion caused by the great interlayer coupling when subjected to an increasing compressive strain. During compression, the conduction band minimum and valence band maximum gradually move closer to the Fermi level and eventually pass through the Fermi surface. Moreover, under large strains, a notable overlap between interlayer electron clouds makes an effective channel for the axial electron transmission, explaining the greatly improved charge transport properties. This improvement is mainly due to the formation of the interlayer transmission channels through σ bonds. Our findings on the strain-regulated electronic properties of helical polymers suggest there are great potential applications of these materials in high-performance sensors and flexible electronic devices. [ABSTRACT FROM AUTHOR]

A simple and environmentally friendly method, based on sequential adsorption of polyacrylamide (PAM) and transition metal ions (Pd2+, Ag+) on zinc oxide precipitated from water solution, was used to synthesize supported mono- and bimetallic catalysts with various Pd:Ag ratios. The catalyst characterization results indicated that PAM and metal ions are completely adsorbed by zinc oxide, forming polymer-stabilized Pd and Ag nanoparticles of 1–3 nm in size, evenly distributed on the support surface. The catalysts were studied in the hydrogenation of phenylacetylene under mild conditions (0.1 MPa, 40 °C). Although Ag-free 1%Pd-PAM/ZnO catalyst presents an interesting catalytic performance (in terms of activity, selectivity, and stability), among PAM-modified catalysts the optimal was 1%Pd–Ag(3:1)-PAM/ZnO, presenting a selectivity to styrene of 88% at 91% conversion of phenylacetylene. For comparison, similar Pd–Ag (3:1) bimetallic catalysts modified with polysaccharides, such as pectin (Pec), chitosan (Chit), and 2-hydroxyethylcellulose (HEC), were studied in the hydrogenation process. The catalysts demonstrated nearly the same selectivity to styrene. The activity of the catalysts decreases in the following order: 1%Pd–Ag(3:1)-HEC/ZnO > 1%Pd–Ag(3:1)-PAM/ZnO > 1%Pd–Ag(3:1)-Pec/ZnO > 1%Pd–Ag(3:1)-Chit/ZnO. [ABSTRACT FROM AUTHOR]

A novel, simple and sensitive fluorescenct method for determination of cysteine in water, milk, milk powder, cabbage, apple, pear and radish was established based on rosamine fluorescent probe. The probe was constructed by rosamine as the signal reporter and phenylalkynyl as the reaction site. Through Michael addition and intramolecular reaction, the probe could detect cysteine with high selectivity and sensitivity. Results indicated that under the optimized conditions of phosphoric acid buffer concentration of 10 mmol/L, pH9.5, methanol/water volume ratio of 1:9 and room temperature reaction for 35 min, the probe selectively recognized cysteine, and its relative fluorescence intensity increased with the increasing of cysteine concentration. Furthermore, the fluorescence signal of the probe had a good linear relationship with cysteine in the concentration range from 18.0 to 70.0 μmol/L (R2=0.992) with detection limit of 0.18 μmol/L. Furthermore, the method was used to determinate cysteine in water, milk, milk powder, cabbage, apple, pear and radish with good recoveries (96.4%~102.97%) and RSD (0.1%～2%). This suggested that the approach would have high selectivity, sensitivity and the feasibility of cysteine detection in practical sample, as well as a good application prospect.

Previously unknown C-19 lappaconitine derivatives were prepared via [3 + 2] cycloaddition reactions of a nitrone based on lappaconitine with compounds containing a triple bond, i.e., propargyl alcohol, methyl propiolate, phenylacetylene, 3-phenoxypropyne-1, and propargyl aldehyde diethylacetal. [ABSTRACT FROM AUTHOR]

A series of non-precious bimetallic NiMx/SiO2 (M = Zn or Co) catalysts with a fixed Ni loading of 5 wt% and different molar ratios of M/Ni (0.004–1.97) were prepared by glucose pyrolysis and applied to the selective hydrogenation of phenylacetylene. The properties of the catalysts were characterized by N2 physisorption, CO chemisorption, ICP-OES, TGA, XRD, HRTEM, XPS, and DRIFTS. The activity and selectivity of the bimetallic catalysts could be tuned by varying the Zn/Ni and Co/Ni molar ratios, which were almost independent of the metal particle size (with a similar size of 4.1–5.5 nm), but predominantly determined by the geometric and/or electronic effects of the catalysts. Among all the catalysts studied, NiZn0.05/SiO2 and NiCo0.09/SiO2 presented higher selectivity to styrene (86.3% and 88.0%, respectively) at above 99% conversion of phenylacetylene. The high selectivity of the former was attributed to the geometric and electronic effects of the Ni–Zn alloy, while the latter was due to the geometric effect caused by the addition of Co. The activity and selectivity of NiCo0.09/SiO2 were maintained during six consecutive cycles, indicating its good stability in the selective hydrogenation of phenylacetylene. [ABSTRACT FROM AUTHOR]

A series of compounds of with high birefringence containing alkoxy–phenylacetylene–isothiocyanato structure were synthesized and characterized. The chemical structures of these compounds were confirmed by FT-IR and 1H-NMR, and transition temperatures and birefringence were measured. One of these compounds with good liquid crystal property and high birefringence was mixed with host liquid crystal to form blend liquid crystal. The effects of the concentration of the compound on phase temperature range, birefringence, resistivity, dielectric anisotropy and photoelectric properties were discussed. The results showed that blend liquid crystal (with 7 wt% compound) exhibited excellent comprehensive performance. [ABSTRACT FROM AUTHOR]

A simple, green and efficient procedure for the synthesis of highly functionalized 3-triazolyl-2-iminochromenes by using a one-pot three component reaction of 2-azido acetonitrile, phenylacetylene and salicylaldehyde in water using CuI/K2CO3 is described. The present protocol offers advantages like high atom economy, simple methodology, shorter reaction time, easy product isolation, no chromatographic purification and avoidance of environmentally hazardous solvents. Compounds 4a-d, 4g-h and 6a-b have been investigated for antioxidant activity. Compound 4c is found to be the most active among the series showing high reducing power and free radical scavenging activity. [ABSTRACT FROM AUTHOR]

Pd-Cu/SiC bimetallic catalysts were prepared by a liquid-phase reduction method and used in the selective hydrogenation of phenylacetylene to styrene. The results show that the mass ratio of Pd/Cu has obvious influence on the catalytic performances, and Pd0.5-Cu2.5/SiC catalyst exhibits the best catalytic activity and selectivity, and the TOF value based on Pd can reach as high as 2 972 h-1. During hydrogenation, H2 dissociates on the surface of Pd to form active hydrogen, and then the active hydrogen overflows to SiC and reacts with phenylacetylene adsorbed on the surface of SiC. XPS results illustrate that the electrons can transfer from Pd to Cu, which decrease the H2 dissociation ability of Pd and hence inhibit the over hydrogenation of styrene. This strategy of constructing bimetallic catalyst by adding transition metal Cu can effectively cut the usage of Pd and reduce the cost of the catalyst. [ABSTRACT FROM AUTHOR]

Photoredox processes have emerged recently as a powerful tool for methodology developments. In this context, the hydrotrifluoromethylation of alkenes and alkynes using visible light photoredox methodologies has proven its efficiency these last years. This micro-review summarizes the latest developments in this field. [ABSTRACT FROM AUTHOR]

In the field of industrial semi-hydrogenation of trace alkynes amidst alkene feedstocks, the pivotal challenge lies in circumventing the hydrogenation of alkenes. Herein, we present Zr(OH) 4 as an innovative catalyst for the semi-hydrogenation of phenylacetylene, demonstrating remarkable selectivity towards styrene (>96 %), while exhibiting inactivity towards free styrene. Notably, Zr(OH) 4 achieves a 95 % conversion of quasi-industry 1 mol % phenylacetylene within styrene, with a mere 0.44 % styrene loss. Experimental and theoretical results confirm both terminal Zr-O-H and bridge Zr-O-H can dissociate H 2 , while the terminal Zr-O-H plays a crucial role on activating phenylacetylene through the sequential hydrogenation process of C 6 H 5 C≡CH→C 6 H 5 C=CH 2 →C 6 H 5 CH=CH 2 . The high rate of phenylacetylene removal is attributed to its strong adsorption capacity, while Zr(OH) 4 has a significantly weaker adsorption capacity for styrene., (© 2024 Wiley-VCH GmbH.)

Silicon quantum dots (Si-QDs) with luminescent downshifting properties have been used for the efficiency enhancement of solar cells. In this study, Phenylacetylene-capped silicon quantum dots (PA Si-QDs) have been fabricated and applied as luminescent downshifting material on polycrystalline silicon solar cells, by dropcasting. The PA Si-QD coated solar cell samples presented an average increase in the short circuit current (Isc) of 0.75% and 1.06% for depositions of 0.15 mg and 0.01 mg on 39 mm × 39 mm pc-Si solar cells, respectively. The increase was further enhanced by full encapsulation of the sample leading to overall improved performance of about 3.4% in terms of Isc and 4.1% in terms of power output (Pm) when compared to the performance of fully encapsulated reference samples. The PA Si-QD coating achieved a reduction in specular reflectance at 377 nm of 61.8%, and in diffuse reflectance of 44.4%. The increase observed in the Isc and Pm is a promising indicator for the use of PA Si-QDs as luminescent downshifting material to improve the power conversion efficiency of pc-Si solar cells. [ABSTRACT FROM AUTHOR]

Mesoporous carbon (MC) has been successfully synthesized via the soft template method and further impregnated with monometallic Ni and bimetallic Ni-Co to give Ni-modified MC (Ni/MC) and NiCo/MC, respectively. The modified MC materials were characterized using XRD, SEM-EDX, SAA, and TEM. The results of the TEM analysis showed that the metal was homogeneously distributed on MC with the average particle sizes of Ni and bimetallic NiCo being 23.1 and 10.4 nm, respectively. The results of BET analysis show that the materials have a high surface area of 304, 289, and 313 m²/g for MC, Ni/MC, and NiCo/MC, respectively. Both Ni/MC and bimetallic NiCo/MC were then used as catalysts in phenylacetylene hydrogenation under atmospheric hydrogen pressure. [ABSTRACT FROM AUTHOR]

The use of a modern homogeneous metal complex catalyst for the hydration of acetylenes is being investigated. The process is relevant both for the industry of basic organic synthesis and for the perfume industry. The analysis of existing processes used in industry for the production of acetaldehyde was carried out. Significant shortcomings of existing processes are revealed: low environmental friendliness and high energy consumption. To solve this problem, the reaction of hydration of an acetylene compound was studied using a modern homogeneous catalyst based on gold, which is not toxic. The study was conducted by selecting aliquots during the reaction. Using the 1H NMR spectroscopy method, the conversion values of phenylacetylene were calculated for the time values corresponding to the moments of aliquot sampling. The reaction order with respect to phenylacetylene was calculated and the reaction constant under the reaction conditions was calculated. When reacting in the presence of the proposed catalyst, a conversion of phenylacetylene of 86.96 % is achieved in 3 hours. The data obtained provide grounds for carrying out the process of catalytic hydration of acetylenes, namely phenylacetylene, with the production of acetophenone, which is important for use in the perfume industry. The data obtained can be applied to the process of hydration of acetylene with the formation of acetaldehyde, which is widely used in the industry of basic organic synthesis. For the process of catalytic hydration of acetylene compounds, a hardware design is proposed, a gas-liquid reactor with a changing hydrodynamic situation, which, together with the product separation column, is combined into a single installation. Using an optimized method, a catalyst based on gold chloride was synthesized from a gold alloy. [ABSTRACT FROM AUTHOR]

The Pd(II) complexes [Pd(Cp)(L)n]m[BF4]m were synthesized via the reaction of cationic acetylacetonate complexes with cyclopentadiene in the presence of BF3∙OEt2 (n = 2, m = 1: L = PPh3 (1), P(p-Tol)3, tris(ortho-methoxyphenyl)phosphine (TOMPP), tri-2-furylphosphine, tri-2-thienylphosphine; n = 1, m = 1: L = dppf, dppp (2), dppb (3), 1,5-bis(diphenylphosphino)pentane; n = 1, m = 2 or 3: 1,6-bis(diphenylphosphino)hexane). Complexes 1–3 were characterized using X-ray diffractometry. The inspection of the crystal structures of the complexes enabled the recognition of (Cp–)⋯(Ph-group) and (Cp–)⋯(CH2-group) interactions, which are of C–H…π nature. The presence of these interactions was confirmed theoretically via DFT calculations using QTAIM analysis. The intermolecular interactions in the X-ray structures are non-covalent in origin with an estimated energy of 0.3–1.6 kcal/mol. The cationic palladium catalyst precursors with monophosphines were found to be active catalysts for the telomerization of 1,3-butadiene with methanol (TON up to 2.4∙104 mol 1,3-butadiene per mol Pd with chemoselectivity of 82%). Complex [Pd(Cp)(TOMPP)2]BF4 was found to be an efficient catalyst for the polymerization of phenylacetylene (PA) (catalyst activities up to 8.9 × 103 gPA·(molPd·h)−1 were observed)

[Display omitted] • The Cu x Co@NC bimetallic catalysts were prepared by dual-regulation strategy. • The Cu x Co@NC catalysts exhibited significant Mott-Schottky effect. • The electronic structure of metallic Co was modulated by Cu and N-doping. • The Cu x Co@NC catalysts presented good semi-hydrogenation of phenylacetylene. Styrene, an important monomer in the production of polystyrene, is usually mixed with a small number of phenylacetylene which readily causes the poisoning of catalyst during styrene polymerization. To address this issue, we reported a nitrogen-doped carbon encapsulated CuCo bimetallic catalyst (Cu x Co@NC) for styrene production from phenylacetylene semi-hydrogenation. The Cu x Co@NC catalyst obtained a 100% conversion of phenylacetylene along with a high 94.6% selectivity of styrene, far higher than those of single metal Co@C and Co@NC catalysts. Detailed characterizations unveiled that the Cu x Co@NC catalyst fabricated by a dual-regulation strategy showed Mott-Schottky effect, in which the electrons transferred from metallic Cu to Co and then to outer N-doped carbon shells. Moreover, the electron transfers of metallic Co could be regulated by Mott-Schottky effect with which to improve the semi-hydrogenation of phenylacetylene to styrene. This work provides an feasible pathway to effectively design the supported metal catalysts for highly selective semi-hydrogenation of alkynes to alkenes. [ABSTRACT FROM AUTHOR]

Single atom alloys (SAAs) have proven to be effective catalysts, offering customizable properties for diverse chemical processes. Various metal combinations are used in SAAs and Pd dispersed materials are frequently employed in catalyzing hydrogenation reactions. Herein, we explore the hydrogenation of phenylacetylene to styrene and ethylbenzene on PdAg SAA using density functional theory calculations. Our results show that while PdAg SAA does improve the activity of the host Ag towards hydrogenation, a dilute PdAg SAA surface with isolated Pd-atoms is not selective towards partial hydrogenation of phenylacetylene. Additionally, we investigate how the size of the reactant molecule, the size of the metal alloy ensemble, and the ligand effect impact the hydrogenation process. The SAA enhances the binding strengths of various organic adsorbates, although this effect diminishes as the adsorbate size increases. Our findings indicate the dilute PdAg exhibits selectivity towards hydrogenation of smaller molecules such acetylene due to its distinct adsorption geometry. The selective hydrogenation of phenylacetylene necessitates a surface Pd dimer ensemble. Our research highlights the importance of both reactant molecule size and surface configurations in SAA catalysts. This is particularly crucial when dealing with the adsorption of sizable organic molecules where the functional group can adopt different adsorption modes. • An extensive study on the hydrogenation of phenylacetylene on PdAg single atom alloy. • The size of the organic reactant affects the activity and selectivity of the hydrogenation process on a SAA. • A Pd-dimer is an active site for selective hydrogenation of phenylacetylene to styrene. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) is a compound that can potentially be used as a carbon source in the synthesis of fine chemicals. However, the utilization of CO2 is still constrained due to its inert and stable nature. Therefore, the presence of a catalyst is needed in CO2 conversion. This study aims to synthesize copper impregnated mesoporous carbon (Cu/MC) as a catalyst for phenylacetylene carboxylation reaction with CO2 to produce phenylpropiolic acid. The synthesis of mesoporous carbon was performed via the soft template method. The as-synthesized Cu/MC material was characterized by FTIR, SAA, XRD, and SEM-EDX. BET surface area analysis of mesoporous carbon showed that the material has a high surface area of 405.8 m2/g with an average pore diameter of 7.2 nm. XRD pattern of Cu/MC indicates that Cu has been successfully impregnated in the form of Cu(0) and Cu(I). Phenylacetylene carboxylation reaction with CO2 was carried out by varying reaction temperatures (25, 50, and 75 °C), amount of catalyst (28.6, 57.2, and 85.8 mg), type of base (Cs2CO3, K2CO3, and Na2CO3), and variation of support. The reaction mixtures were analyzed by HPLC and showed that the highest phenylacetylene conversion of 41% was obtained for the reaction at 75 °C using Cs2CO3 as a base.

The platinum nanocomposites with mesoporous carbon nitride (Pt/mpg-C3N4) were synthesized by in situ reduction of H2PtCl6·6H2O with aqueous methanol and studied as catalysts in phenylacetylene hydrogenation in the gas phase at 150 °C and atmospheric pressure in the flow process. The efficiency of hydrogenation can be enhanced by using available organic modifiers. The addition of pyridine, piperidine, or morpholine to the starting solution of phenylacetylene in hexane provides 95–100% conversion and 90–92% selectivity to styrene on the Pt/mpg-C3N4 catalyst. A sharp increase in the selectivity to styrene without substantial changes in conversion is observed when THF, ethanol, triethylamine, dioxane, or chloroform are used as diluents. No loss of activity or selectivity was observed during 10-h tests of the catalyst in the flow process. [ABSTRACT FROM AUTHOR]

[Display omitted] • The fully exposed cobalt nanoclusters over nitrogen-doped carbon support were created by a host–guest strategy. • This catalyst shows excellent catalytic efficiency in semi-hydrogenation of phenylacetylene. • DFT calculations reveal that the high selectivity originates from the highly exposed cobalt nanoclusters. • A wide substrate scope and a broad functional-group tolerance were also demonstrated. Atomically dispersed nanocluster catalysts with fully available metal active sites can maximize atom utilization efficiency and deliver unique catalytic performance relative to nanoparticle and single-atom counterparts. Herein, we report a host–guest strategy by synergizing metal-support interaction and spatial confinement effect to access fully exposed cobalt nanoclusters over nitrogen-doped carbon as a highly active, selective, and reusable catalyst (Co loading of 1.6 wt%) for semi-hydrogenation of phenylacetylene. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy, X-ray photoelectron spectroscopy, and CO-absorbed diffuse reflectance infrared Fourier transform spectroscopy collectively confirm the cobalt nanoclusters were loosely bonded and randomly dispersed over the nitrogen-doped carbon support. This catalyst, with a full metal availability to the reactants, shows an exceptional catalytic activity (turnover frequency of 3132 h−1) and selectivity (92%) in the semi-hydrogenation of phenylacetylene (1 atm H 2 @60 °C), superior to most of the previously reported catalysts. In addition, this catalyst exhibits a wide substrate scope and broad functional-group tolerance. This work may provide an avenue for the design and facile synthesis of fully exposed metal catalysts with high activity. [ABSTRACT FROM AUTHOR]

BACKGROUND: The development of highly efficient and selective bimetallic catalytic systems for the hydrogenation of unsaturated compounds is an important scientific task. RESULTS: A new bimetallic 1%Cu‐1%Pt/SiO2 catalyst for the selective hydrogenation of phenylacetylene was developed. The bimetallic catalysts were prepared by a consecutive incipient wetness impregnation method and a redox method with preadsorbed hydrogen. We showed that the catalytic properties of 1%Cu‐1%Pt/SiO2 catalysts and selectivity toward styrene depend on the states of metals and interactions between Cu and Pt in bimetallic particles. The strong contact interaction between Pt0, Ptδ– and Cu<2+ in sample prepared by the impregnation method provides a high selectivity of about 82% in styrene formation, while the interaction between PtO and CuO phases provides a 60% selectivity under mild conditions. CONCLUSIONS: A new highly effective bimetallic Cu‐Pt/SiO2 catalyst was found for the selective hydrogenation of phenylacetylene with the formation of styrene. © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

This paper reports the use of rhodium (Rh) catalysts for the oxidative coupling reaction between phenylacetylene and benzaldehyde derivatives via C-H bond activation. These reactions were catalyzed by Rh(l-amino acid)(cod) (the l-amino acid is l-phenylalanine, l-valine or l-proline; cod is 1,5-cyclooctadiene) to obtain chromones in 12.7–88.3% yield. These new Rh catalysts have excellent activity for the coupling reaction between phenylacetylene and different benzaldehyde derivatives. It was found that the electronic effects of the benzaldehyde derivative substituent affected the reaction yield, which is in accordance with the proposed mechanism.

Phenylacetylene as an impurity in styrene is poisonous to catalysts for styrene polymerization in the production of polystyrene plastics. The selective hydrogenation of phenylacetylene to styrene is an industrially promising route to overcome this challenge yet lacks cost‐effective catalysts to prevent the overhydrogenation of styrene to ethylbenzene. In this work, we report an efficient and robust copper‐decorated Rh/TiO2 catalyst for the selective hydrogenation of phenylacetylene to styrene. By optimizing the copper coverage on TiO2 supported Rh nanoparticles, we achieved a selectivity of 83% towards styrene formation at a phenylacetylene conversion of 93%. The appropriate Cu coverage is found to modulate the electronic states of surface Rh atoms and changes the Rh exposed active sites, weakening the binding strength of alkene and hydrogen intermediates on Rh and thus mitigating the overhydrogenation and enhancing the selectivity for styrene generation. This work offers insights on the rational design of efficient Rh‐based bimetallic catalysts for selective hydrogenation of phenylacetylene to styrene. [ABSTRACT FROM AUTHOR]

The cascade reactions of phenylacetylene to ethylcyclohexane and 1-phenyl-1-propyne to propylcyclohexane were studied individually, under deuterium and competitively at 343 K and 3 barg pressure over a Rh/silica catalyst. Both systems gave similar activation energies for alkyne hydrogenation (56 ± 4 kJ mol−1 for phenylacetylene and 50 ± 4 kJ mol−1 for 1-phenyl-1-propyne). Over fresh catalyst the order of reactivity was styrene > phenylacetylene ≫ ethylbenzene. Whereas with the cascade hydrogenation starting with phenylacetylene, styrene hydrogenated much slower phenylacetylene even once all the phenylacetylene was hydrogenated. The activity of ethylbenzene was also reduced in the cascade reaction and after styrene hydrogenation. These reductions in rate were likely due to carbon laydown from phenylacetylene and styrene. Similar behavior was observed with the 1-phenyl-1-propyne cascade. Deuterium experiments revealed similar positive KIEs for phenylacetylene (2.6) and 1-phenyl-1-propyne (2.1). Ethylbenzene hydrogenation/deuteration gave a KIE of 1.6 obtained after styrene hydrogenation in contrast to the inverse KIE of 0.4 found with ethylbenzene hydrogenation/deuteration over a fresh catalyst, indicating a change in rate determining step. Competitive hydrogenation between phenylacetylene and styrene reduced the rate of phenylacetylene hydrogenation but increased selectivity to ethylbenzene suggesting a change in the flux of sub-surface hydrogen. In the competitive reaction between 1-phenyl-1-propyne and propylbenzene, the rate of hydrogenation of 1-phenyl-1-propyne was increased and the rate of alkene isomerization was decreased, likely due to an increase in the hydrogen flux for hydrogenation and a decrease in the hydrogen species active in methylstyrene isomerization. [ABSTRACT FROM AUTHOR]

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The catalytic hydrogenation of a carbon–carbon triple bond in acetylene compounds is an important industrial process in which high selectivity toward olefin compounds must be ensured. This work considers the effect of treating palladium catalysts based on hyper-cross-linked polystyrene (HPS) with sodium carbonate on the activity and selectivity in the hydrogenation of 2-methyl-3-butyn-2-ol and phenylacetylene is considered. The effect of such treatment depends on the palladium precursor and the polymer support (HPS non-functionalized or HPS containing tertiary amino groups). Selectivity in the hydrogenation of 2-methyl-3-butyn-2-ol (95% conversion of the substrate) is 98% at ambient hydrogen pressure and 90°C in toluene for 1%-Pd/HPS catalysts treated with Na2CO3 and 99.5% in the hydrogenation of phenylacetylene. [ABSTRACT FROM AUTHOR]

Copyright of Precious Metals / Guijinshu is the property of Precious Metals Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Phenylacetylene is of significance in polycyclic aromatic hydrocarbon (PAH) growth in combustion systems, especially as the key intermediate species in the hydrogen abstraction carbon addition sequence. The consumption of phenylacetylene via H-atom abstraction reactions forming ortho-C 6 H 4 C 2 H (o-C 6 H 4 C 2 H) radical and its subsequent reaction with carbon addition are important steps in PAH growth. Nevertheless, rate constants for H-atom abstraction reactions from phenylacetylene have not been explored theoretically in the literature. As regards carbon addition, besides acetylene, ethylene is also presented in large concentrations in e.g., ethylene and propene flames. However, its role in PAH growth has not been well addressed yet. In this study, the H-atom abstraction reactions from phenylacetylene aromatic ring sites (ortho-, meta-, para-) by both H atoms and OH radicals, and the subsequent C 2 H 4 addition to o-C 6 H 4 C 2 H radical are accurately determined with electronic structure calculations. The main bimolecular product from the potential energy surface of the C 2 H 4 addition to o-C 6 H 4 C 2 H is 2-ethynylstyrene + H, while naphthalene + H and 1-methyleneindene + H are preferred to form at high temperatures and low pressures. Rate constants are lumped with an automated master equation-based lumping approach and integrated into a recently developed chemical kinetic model. Updates of the phenylacetylene-related reactions are tested by ethylene and benzene copyrolysis in shock tube, and ethylene oxidation in laminar premixed and counterflow diffusion flames. Reaction flux analysis are additionally performed regarding the phenylacetylene consumption and naphthalene formation. [ABSTRACT FROM AUTHOR]

The novel Pd‐nanocomposites, fabricated via calcination of the MOF [Pd(2‐pymo)2]n (2‐pymo=2‐pyrimidinolate), were used for the first time in the transfer hydrogenation of phenylacetylene with NaBH4. The presence of Pd NPs or PdO in the studied materials was evidenced by XPRD, Raman spectroscopy, XPS and HR‐TEM. Under mild reaction conditions, in water as a solvent, Pd‐nanocomposites, Pd/CPYMO and PdO/Pd/CPYMO, provided better catalytic results than the pristine [Pd(2‐pymo)2]n, producing styrene with good selectivity. These two catalysts showed also good durability in subsequent reuses, while the productivity of PdO/CPYMO decreased after the second run. [ABSTRACT FROM AUTHOR]

Supported catalysts have attracted extensive attention due to their excellent catalytic performance and reliability in heterogeneous catalysis. In this work, we report a general synthesis strategy that achieves the self‐coupling reaction of acetylene derivatives to 1,3‐diyne efficiently under conditions of copper catalyst impregnated on the precursor formed by acetone and urea. The experiments were performed by screening the base, solvent, temperature, and so forth to determine the optimum reaction conditions and then characterization and analysis of the catalyst. The results demonstrate that the Cu/CuO@CN(8) exhibits extraordinary reactivity to the self‐coupling reaction and achieves a high turnover frequency (TOF = 96.8). Typically, the conversion of phenylacetylene reaches 99.9% under the optimal reaction conditions of NaOH (2 mmol) and tert‐butanol (2 ml) and O2 (1 atm) at 60°C for 1 h. Nevertheless, it is worth noting that Cu/CuO@CN(8) has a large specific surface area (626.07 m2 g−1) and low metal loading (3.3%) measured by Brunauer Emmett–Teller (BET) and ICP‐OES, respectively. Simultaneously, kinetics and mechanism are also discussed and analyzed, and the thermodynamic energy value is calculated as 22.74 kJ mol−1. Besides, the optimum catalyst can be reused five times under optimal conditions without a significant decrease in reactivity. [ABSTRACT FROM AUTHOR]

Background. On the base of local raw materials, by-products and waste products of their processing with using new catalytically active catalysts with high selectivity and stability, were synthesized acetylene alcohols and their derivatives which are used as ionites, inhibitors, biocides, solutions, crosslinking and binding agents in the chemical, petroleum, textile, and pharmaceutical industries and correspondly their synthesis and production is one of the urgent problems. Purpose. Synthesis of aromatic acetylene alcohols by enantioselective alkylation of aldehydes of various nature with phenylacetylene, study of their physico-chemical properties and determination of ranges of applications. Investigation of the effect of complex catalytic systems prepared on the base of titanium tetraisopropyloxide on the synthesis of selected alcohols, determinftion the composition, types and amount of intermediate and by-products formed in the process, and being ways of their using. Methodology. Methods for the synthesis of aromatic acetylene alcohols were elaborated using enantioselective alkylation reaction with phenylacetylene in the presence of some aldehydes--acetic aldehyde, croton aldehyde, cyclogexane cardegide and benzaldehyde with using new catalytic systems, which were based on titanium tetraisopropyloxide. The purity and structure of the synthesized compounds were analyzed by modern physical and chemical research methods, their biological activity is studied and the areas of their application in industrial enterprises were determined. Originality. For the first time aromatic acetylene alcohols such as 4-phenylbutin-3-ol-2, 1- phenylhexene-4-in-1-ol-3, 1-cyclohexyl-3-phenylpropine-2-ol-1, 1,3-diphenylpropine-2-ol-1 were synthesized with using new complex catalytic systems ZnEt2/Ti(OiPr)4/PhMe and EtMgBr/Ti(OiPr)4/PhMe. The influence of the selected catalytic systems, the structure and nature of the aldehydson the product yield was scientifically determined. Mechanisms of reactions of synthesis of acetylene alcohols are proposed and recommendations on the fields of application are presented. Findings. 4-phenylbutin-3-ol-2, 1-phenylhexene-4-in-1-ol-3, 1-cyclohexyl-3-phenylpropine-2-ol-1, and 1,3-diphenylpropine-2-ol-1 were synthesized using the enantioselective alkylation of some aldehydes in the presence of phenylacetylene, the most alternative reaction conditions and activation energies were found, and reaction mechanisms were proposed. The effects of the reaction duration, temperature, amount of reagents and substrates, solvents and catalytic ligands on the product yield were systematically studied. The composition, structure and purity of the obtained compounds were analyzed by modern physical and chemical methods, energy and quantum chemical properties are calculated, and their using different ranges of industry has been preposed. [ABSTRACT FROM AUTHOR]

The hypotheses about reasons for the inverse dependence of the turnover frequency of hydrogenation of unsaturated compounds (alkyne, alkynol, olefin) on the catalyst concentration were discriminated by kinetic methods combined with electron microscopy. The reasons are: dissociation of polycrystalline Pd–P particles, equilibrium shift (stabilized cluster–cluster + stabilizer), and aggregation–disaggregation of Pd–P particles, the latter being the main reason for the concentration range 0.125–1 mmol/L. The effect of aggregation–disaggregation of Pd–P particles on the catalyst activity differs depending on the substrate. The proposed kinetic model was shown to be consistent with the experimental data for styrene hydrogenation used as an example. The rate constants of some stages were determined. [ABSTRACT FROM AUTHOR]

The effect of pectin, gellan, and chitosan on the activity, stability, and styrene selectivity of supported palladium catalysts for the selective hydrogenation of phenylacetylene was determined. It was shown that a positive effect is achieved as a result of the formation of palladium nanoparticles with a size of 1-4 nm, which are distributed relatively uniformly over the surface of the carriers, when polysaccharides are added in the catalytic system. [ABSTRACT FROM AUTHOR]

We report a new design of polymer phenylacetylene (PA) ligands and the ligand exchange methodology for colloidal noble metal nanoparticles (NPs). PA-terminated poly(ethylene glycol) (PEG) can bind to metal NPs through acetylide (M-C≡C-R) that affords a high grafting density. The ligand-metal interaction can be switched between σ bonding and extended π backbonding by changing grafting conditions. The σ bonding of PEG-PA with NPs is strong and it can compete with other capping ligands including thiols, while the π backbonding is much weaker. The σ bonding is also demonstrated to improve the catalytic performance of Pd for ethanol oxidation and prevent surface absorption of the reaction intermediates. Those unique binding characteristics will enrich the toolbox in the control of colloidal surface chemistry and their applications using polymer ligands.

Semi-hydrogenation of alkynes to alkenes is one of the most important industrial reactions. However, it remains technically challenging to obtain high alkene selectivity especially at a high alkyne conversion because of kinetically favorable over hydrogenation. In this contribution, we show that supported ultrasmall Pt nanoparticles (2.5 nm) on mesoporous TiO2 (Pt@mTiO2) remarkably improve catalytic performance toward semi-hydrogenation of phenylacetylene. Pt@mTiO2 is prepared by co-assembly of Pt and Ti precursors with silica colloidal templates via an evaporation-induced self-assembly process, followed by further calcination for thermal decomposition of Pt precursors and crystallization of mTiO2 simultaneously. As-resultant Pt@mTiO2 discloses a high hydrogenation activity of phenylacetylene, which is 2.5 times higher than that of commercial Pt/C. More interestingly, styrene selectivity over Pt@mTiO2 remains 100% in a wide phenylacetylene conversion window (20–75%). The styrene selectivity is >80% even at 100% phenylacetylene conversion while that of the commercial Pt/C is 0%. The remarkable styrene selectivity of the Pt@mTiO2 is derived from the weakened styrene adsorption strength on the atop Pt sites as observed by diffuse reflectance infrared Fourier transform spectroscopy with CO as a probe molecule (CO-DRIFTS). Our strategy provides a new avenue for promoting alkyne to alkene transformation in the kinetically unfavorable region through novel catalyst preparation.

Pyrolysis of phenylacetylene with and without the presence of C 2 hydrocarbons (acetylene or ethylene) was studied in a single-pulse shock tube coupled to gas chromatography/gas chromatography-mass spectrometry equipment for speciation diagnostics. Quantitative speciation profiles were probed from each reaction system over the temperature range of 1100–1700 K at a nominal pressure of 20 bar. A kinetic model was proposed to interpret how phenylacetylene is consumed under high-pressure pyrolytic conditions and how the resulting intermediates react to form polycyclic aromatic hydrocarbons (PAHs), and furthermore, how the extra acetylene or ethylene alter the reaction schemes. It was found that the bimolecular reaction between phenylacetylene and hydrogen atom leading to phenyl and acetylene dominates phenylacetylene decomposition throughout the temperature window. The addition/elimination reactions between phenylacetylene and phenyl not only produce hydrogen atoms to maintain the reactivity of the fuel decay, but also directly lead to the formation of several C 14 H 10 PAH isomers including diphenylacetylene, 9-methylene-fluorene and phenanthrene. Intermediates pools, regarding both species categories and abundance, are changed by the two C 2 fuels introduced into the reaction system. The added acetylene enables the Hydrogen-Abstraction-Acetylene-Addition (HACA) mechanism starting from the phenylacetylene radical to occur at relatively low temperatures. But the yielded naphthyl core does not stabilize in naphthalene due to the lack of hydrogen atoms in the reaction system, and instead, it carries on the HACA route by further combining with another acetylene molecule, ending up in acenaphthylene. Differently, the added ethylene intensifies the HACA routes by contributing to the acetylene formation, and more importantly, provides hydrogen atoms participating in the naphthalene formation from naphthyl radical. [ABSTRACT FROM AUTHOR]