Reaction Of Carbonate Research Articles

Insights on the polymerization kinetics of non-isocyanate polyurethanes (NIPU) using in situ NMR spectroscopy

An in situ characterization method using liquid Nuclear Magnetic Resonance (NMR) spectroscopy has been developed to aid the preparation of highly reactive non-isocyanate polyurethanes (NIPUs) from cyclic carbonate aminolysis. Using this methodology, the aminolysis kinetics and the final polymer structure of a model NIPU obtained by reaction of a 5-membered bis-cyclic carbonate (5CC) and 1,4-diaminobutane have been fully investigated, as a function of the type and concentration of the aminolysis catalyst, and the reaction temperature. Several catalysts already reported in NIPUs syntheses, including 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), have been compared. The kinetics of the 5CC hydrolysis side reaction was also studied. With an activation energy of 29.7 kJ mol−1, TBD was clearly the most efficient catalyst used, allowing 5CC conversion ratio of up to 100 % using a concentration of 0.35 eq5CC. However, under these experiment conditions, TBD concentration also showed to have a non-negligible influence on the hydrolysis rate, representing between 6 and 14 % of the initial 5CC concentrations, at 353 K. Neither the catalyst or the temperature seemed to affect the polymer structure, with secondary hydroxyl-containing isomer proportions of (70 ± 6) %. Finally, this in situ NMR method is paving the way for rapid screening of innovative catalysts for sustainable NIPU synthesis.

Asymmetric Allylic Amination of Alkyl-Substituted Allylic Carbonates with Pyridones Catalyzed by the Krische Iridium Complex.

An efficient Ir-catalyzed asymmetric allylic amination reaction of alkyl-substituted allylic carbonates is disclosed. With the Krische iridium complex as the catalyst, asymmetric allylic amination of alkyl-substituted allylic carbonates with pyridones proceeds effectively, affording pyridone derivatives containing a stereocenter α to the nitrogen atom in excellent yields and enantioselectivity (up to 99% yield, 95% ee). This catalytic system broadens the substrate scope of the reaction compared with that of the known catalytic systems. This reaction can also be conducted on a gram scale, further enhancing its potential for synthetic application.

Aminolysis of five-membered cyclic carbonate catalyzed by guanidines: Solvent effects on the formation of guanidine dimers

This paper presents an experimental and computational investigation on the aminolysis reactions of five-membered cyclic carbonate (5CC) catalyzed by mono- or bi-cyclic guanidines in various solvents. For both liquid and solid 5CC substrate employed, higher polar solvent favors the monomeric active guanidine responsible for the catalytic aminolysis reactions. The formation of the dimeric state of the guanidine catalyst, which is seemingly inert to catalytic activity, is prevented by the bulkier substituents connecting to the guanidine moiety. Extensive DFT calculations further confirm that the relative stabilities of dimeric guanidine is depended on both the polarities of the solvents and the bulkiness of the substituents connected to the guanidine moiety, which is consistent with the experimental kinetic results.

Mild and Catalytic Synthesis of Pyrroles from Vinyl Ethynylethylene Carbonates.

A tandem remote propargylic amination/ring closure/aromatization reaction of vinyl ethynylethylene carbonates and amines has been developed, successfully constructing pyrrole derivatives. The reaction features mild conditions, high regioselectivity, high yields, and good functional group tolerance, making it an efficient method for pyrrole synthesis. Importantly, a variety of substrates containing natural product skeletons could also be compatibly and efficiently converted into pyrroles under the reaction conditions.

Pyridine-Catalyzed Chemoselective Four-Component Cascade Reaction of Aromatic Aldehydes, Malononitrile/Cyanoacetates, MBH Carbonates, and Alcohols.

An efficient pyridine-catalyzed chemoselective four-component cascade reaction of aromatic aldehydes, malononitrile/cyanoacetates, Morita-Baylis-Hillman (MBH) carbonates, and alcohols has been established. This one-pot reaction progressed in an unusual reaction with solvent participation via a Knoevenagel condensation/oxa-Michael addition/SN2' substitution sequence. This method allowed for facile access to an array of functionalized chain alkylbenzenes and dihydroquinolinones bearing one all-carbon quaternary center in moderate to excellent yields. It is worth noting that the configuration of the all-carbon quaternary center could be modulated by changing only the electron-withdrawing groups via a tandem reduction/cyclization reaction.

Photoinduced Copper‐Catalyzed Three‐Component Radical Carboamination of Styrene Derivatives

The catalytic three‐component radical carboamination of alkenes has recently emerged as an alternative and robust platform for the rapid construction of diverse and valuable amines. Despite great advances in this field, new methods that enable highly selective access to new chemical space surrounding the amine functional groups are still in high demand. Herein, we report a generally applicable visible light‐induced copper‐catalyzed three‐component radical cyanoalkylamination reaction of alkenes, oxime carbonates, and benzoyloxycarbamates. This protocol demonstrates high chemo‐selectivity, broad substrate scope, and good functional group tolerance, providing access to a variety of cyanoalkylated aliphatic amines with good yields.

Recent Advances in the Reaction of MBH Carbonates: Scope and Mechanism

AbstractIn recent years, Morita‐Baylis‐Hillman (MBH) carbonates have been extensively used in domino reactions for the synthesis of novel cyclic and acyclic compounds. This review highlights the progress made in the last decade in the synthesis of a series of compounds from an uncyclized reaction or annulation of MBH carbonates, which demonstrates that the excellent reactivity and high research value of MBH carbonates as representative substrates in organic synthesis. We hope the summary and understanding of the reactivity of MBH carbonates can inspire chemists to apply these substrates in the design of more efficient domino reactions, which will be beneficial for the organic synthesis and drug chemistry.

The reactivity of α-tricalcium phosphate powders is affected by minute amounts of β-calcium pyrophosphate and by the synthesis temperature

α-tricalcium phosphate (α-TCP) is the most widespread raw material for hydraulic calcium phosphate cements (CPCs). CPCs are widely used in bone repair due to their injectability, setting ability, and osteoconductivity. This study investigated the reactivity of α-TCP powders, focusing on the impact of minor phase impurities, β-calcium pyrophosphate and hydroxyapatite, and the synthesis temperature. The α-TCP powders were synthesized via a solid-state reaction of calcium carbonate and anhydrous dicalcium phosphate, with varying Ca/P molar ratios (1.4850–1.5075) and synthesis temperatures (1175°C–1350 °C). Powders produced with a Ca/P molar ratio below 1.50 and synthesized at a temperature above the melting point of β-CPP (1296 °C) had a broader size distribution and a two to fourfold lower hydraulic reactivity. Conversely, a higher Ca/P molar ratio improved reactivity. The study underscores the importance of precise control over synthesis parameters to enhance the performance of α-TCP-based CPCs, offering insights for optimizing material design in biomedical applications.

Study on a New Reactive Dividing-Wall Column for the Reaction of Vinyl Carbonate and Methanol Ester Exchange to Produce Dimethyl Carbonate

Study on a New Reactive Dividing-Wall Column for the Reaction of Vinyl Carbonate and Methanol Ester Exchange to Produce Dimethyl Carbonate

Revisit coupling of CO2 to ethylene carbonate with an integrated imidazolium and zinc halides catalyst by a study on its decomposition: Active center and mechanism

Coupling of carbon dioxide (CO2) to cyclic carbonates with an epoxide and further into linear carbonates as the indispensable solvents for the lithium-ion batteries has been being one of the hottest topics in transforming CO2 into high value-added chemicals. Nevertheless, the extremely ultrahigh purity requirement for them causes a low efficiency and a modest yield due to the undesired reactions and byproducts occurring in the separation and purification sections. In this work, a novel imidazolium based ionic liquid catalyst system with different anions and cations was studied by a thorough insight into the decomposition reaction of ethylene carbonate (EC), which reveals the synergistic mechanism of the composite catalysts both in section of cyclic carbonate separation from the catalyst for recirculated utilization and purification from the byproducts, and in section of synthesis with high efficiency. Effects of imidazolium cations and halogen anions in the ionic liquid molecule on EC decomposition were investigated by the elaborately designed experiments, thermodynamic estimations, molecular dynamics simulation and DFT assessment. It was found that combining imidazole salts and zinc halides can greatly boost the activity of EC synthesis and decomposition with the effective structure of catalytic center being [EMIm]ZnX4. Furthermore, it was indicated that Br- has a higher activity for EC synthesis and its reversed pyrolysis, while Cl- will promote a side reaction of ring-opening polymerization of EC. Finally, a most favorable catalyst composition with ZnBr2 and [EMIm]Br for EC synthesis was achieved with a high efficiency in synthesis and a low tendency to initiate the side reactions in separation section.

Cathode Electrolyte Interphase Engineering for Prussian Blue Analogues in Lithium-Ion Batteries.

The increasing use of low-cost lithium iron phosphate cathodes in low-end electric vehicles has sparked interest in Prussian blue analogues (PBAs) for lithium-ion batteries. A major challenge with iron hexacyanoferrate (FeHCFe), particularly in lithium-ion systems, is its slow kinetics in organic electrolytes and valence state inactivation in aqueous ones. We have addressed these issues by developing a polymeric cathode electrolyte interphase (CEI) layer through a ring-opening reaction of ethylene carbonate triggered by OH- radicals from structural water. This facile approach considerably mitigates the sluggish electrochemical kinetics typically observed in organic electrolytes. As a result, FeHCFe has achieved a specific capacity of 125 mAh g-1 with a stable lifetime over 500 cycles, thanks to the effective activation of Fe low-spin states and the structural integrity of the CEI layers. These advancements shed light on the potential of PBAs to be viable, durable, and efficient cathode materials for commercial use.

Transesterification of Dimethyl Carbonate with Ethanol Catalyzed by Guanidine: A Theoretical Analysis.

Density-functional theory (DFT) was performed to investigate the mechanistic features of different guanidine-based catalysts, namely, 1,1,3,3-tetramethyl guanidine (TMG) and 1,5,7-triaza-bicyclo-[4.4.0]dec-5-ene (TBD), for the transesterification reaction of dimethyl carbonate (DMC) with ethanol (EtOH). Different possible pathways were suggested in which these catalysts act as either nucleophile or base within a homogeneous system. The DFT results allowed not only the study of the thermochemistry aspects of all elementary reactions featured in the two different activation modes but also the accurate calculation of the free energy barriers for each case. Our findings showed that the catalyzed reaction proceeded through simultaneous activation of DMC and EtOH, facilitated by hydrogen bonding for both catalysts. This feature led to the formation of a stable intermediate with a relatively low free energy barrier. TBD exhibited a potentially more efficient mechanism, owing to its planar structure and dual-activation mode. The free energy barrier of the rate-limiting step, identified as the formation of a zwitterionic complex, then declined by approximately 50% when compared with the reaction without catalysts. Overall, the DFT approach provides good insight into the reactivity of both catalysts and helps to find possibilities for further enhancing the mechanistic features of both catalysts for this type of transesterification reaction.

Asymmetric synthesis of allylic sulfonamides with axially and central chirality via palladium-catalyzed of atroposelective N-allylic alkylation

Axially chiral anilide compounds are an emerging but scarcely investigated class of stereogenic molecules with potential applications as chiral catalysts, biologically active scaffolds and functional materials. Compared to the C–C axially chiral molecules, the synthesis of axially chiral anilide compounds is a challenge owing to the lower rotation barriers. Herein, the construction of chiral allylic amine bearing axial chirality and central chirality via Pd-catalyzed atroposelective N-allylic alkylation reaction of cyclic vinyl carbonates and sulfonamides is reported. A diverse range of chiral sulfonamides bearing axial chirality and central chirality were synthesized in high yields and excellent enantioselectivities (up to 92 ​% yield and 99 ​% ee). In addition, the practical application of this protocol was also demonstrated by gram-scale synthesis and derivatives of the compound.

Efficient ionic transport over wide temperature range in oxide enabled by interfacial reaction of molten carbonate

The development of solid oxide fuel cell (SOFC) operated at low and intermediate temperatures is limited by the poor performance of inorganic ionic conductors. Oxide-based ion conductors have attracted much attention due to their excellent stability and tunable ion conduction behavior. In this study, we propose a new approach for the construction of regulated ionic transport pathways in a composite oxide ionic conductor made of WO3/ZrO2 (WZ) and (Li0.68K0.32)2CO3. The interfacial reaction between WO3/ZrO2 and (Li0.68K0.32)2CO3 is used to enhance the interaction between the oxide and carbonate interfaces and introduce hydrophilic phases for water retention, thus achieving ultra-high ionic conductivity of the oxide/carbonate composites at low and intermediate temperatures. The optimal ionic conductor, 13WZ-30(Li0.68K0.32)2CO3 (13WZ-30C), has a superior ionic conductivity of 25.8-6.28 mS cm−1 from room temperature to 250 °C. The ion conduction mechanism of the composite is investigated. This study emphasizes the significance of interfacial chemistry regulation between oxides and carbonates for achieving superior ion conduction performance.

Mechanism of Fe-skarn formation in the Nanminghe iron deposit, China

Skarn iron deposits are important resources for iron-rich ores and their genesis has been a topic of debate. The Nanminghe iron deposit is a typical skarn iron deposit in Wu’an, Hebei Province, China which provides a good example to investigate the metallogenic mechanism. In this paper, we present a detailed study of the geology, petrography, and geochemical characteristics of magnetite in the Nanminghe iron deposit. Two types of magnetite can be identified in the massive ores: Mag1 is euhedral with radial cracks developed in the margin. It is a low-Si magnetite, with SiO2 content ranging from 0.07% to 0.92%, with an average value of 0.49%. The SiO2 content of Mag2 is from 0.90% to 3.29%, and an average value of 2.03%. The Mag2 is associated with quartz, goethite, and apatite. Geochemical characteristics of Mag1, together with the ore textures suggest its crystallization from an iron magma. There are significant differences in the geochemical characteristics between Mag1 and Mag2. Mag2 is rich in Nb, Ta, high field strength elements, large ion lithophile elements and has higher silica content. The Nb/Ta of Mag2 is higher than that of the original mantle. These characteristics as well as La/Ta vs Th/La, Th/U vs Sm/Nd and Nb/Ta vs Nb features show that Mag2 is formed in the environment of supercritical fluids. The δ56Fe of Mag1 is 0.157‰-0.172‰, with an average value of 0.166‰, and the δ56Fe of Mag2 is 0.119‰-0.160‰, with an average value of 0.139‰. The Fe isotope of Mag2 is lighter than Mag1. There is a negative correlation between δ56Fe and SiO2 of Mag1 and Mag2, suggesting that the lighter δ56Fe of Mag2 was caused by injection of Si-rich fluids. We propose a genetic model where we envisage that the iron-rich melt formed in the deep magma chamber by reaction of dioritic rocks and carbonates. Mag1 formed by cooling of the iron-rich magma, following which Si-rich supercritical fluid were injected into the deep chamber resulting in fluid overpressure. The iron-bearing melt-fluid migrated upward along the magmatic conduit, when Mag2 formed. Our study provides insights into the formation mechanism of skarn iron deposits.

Diphenyl Carbonate: Recent Progress on Its Catalytic Synthesis by Transesterification

Diphenyl carbonate is one of the raw materials used for the synthesis of polycarbonate, and its green and clean production is of great importance to the non-phosgene process for polycarbonate. The production of diphenyl carbonate by transesterification is its representative process route and is considered to be one of the typical examples of a green and sustainable process for chemicals. Since the discovery of the transesterification catalyst for diphenyl carbonate in the 1970s, researchers have been committed to improving its catalytic activity and selectivity and, correspondingly, the reaction engineering process. However, thermodynamic limitations, low activity, low selectivity, and limited stability have been bottlenecks that the transesterification catalyst has not been able to completely overcome, and the improvement of the catalyst is still ongoing. Therefore, this review takes the transesterification reaction of dimethyl carbonate and phenol as a model reaction and, based on a review of the progress in catalyst research on catalytic reaction processes, tries to clarify the structure–activity relationship between catalytic active sites and catalytic performance in homogeneous and heterogeneous catalytic processes and provides an overview of the progress in catalyst synthesis and modification.

Copper‐Catalyzed Formal [4+2] Cycloaddition of Ethynylethylene Carbonates for the Construction of 3,4‐Dihydro‐2H‐benzo[b][1,4]oxazines

A formal [4+2] cycloaddition reaction of ethynylethylene carbonates and 2‐aminophenols has been developed for the synthesis of 3,4‐dihydro‐2H‐benzo[b][1,4]oxazines bearing quaternary carbon atoms. The reaction features mild reaction conditions, good functional group compatibility and good yields. Furthermore, when using chiral PyBox ligand, this strategy could also achieve the asymmetric synthesis of 3,4‐dihydro‐2H‐benzo[b][1,4]oxazines. Application studies indicated that the hydroxymethyl group of final products was an excellent functional group that can be further modified easily.

Facile one-pot synthesis of niobium-containing carbon nitride and the catalytic application for synthesis of dimethyl carbonate

Dimethyl carbonate (DMC) is a building block in wide chemical-related fields and the transesterification of ethylene carbonate (EC) and methanol/ethanol is a sustainable route for the synthesis of DMC. Herein, in order to explore efficient heterogeneous catalysts, niobium-containing carbon nitride materials were synthesized by a convenient one-pot calcination method. By reserving the main chemical functionalities of carbon nitride, the Nb-CN composites contained both acidic and basic properties, and Nb can be dispersed by carbon nitride. In the transesterification of EC with methanol, under the reaction temperature of 140 °C and reaction time of 4 h, the conversion of EC and the selectivity of DMC reached 53.8% and 100%, respectively, and the activity of the catalyst did not decrease significantly after several recycling runs. Furthermore, the Nb-CN could promote transesterification reactions of other cyclic carbonate and alcohols.

Activating reversible carbonate reactions in Nasicon solid electrolyte-based Na-air battery via in-situ formed catholyte

Out of practicality, ambient air rather than oxygen is preferred as a fuel in electrochemical systems, but CO2 and H2O present in air cause severe irreversible reactions, such as the formation of carbonates and hydroxides, which typically degrades performance. Herein, we report on a Na-air battery enabled by a reversible carbonate reaction (Na2CO3·xH2O, x = 0 or 1) in Nasicon solid electrolyte (Na3Zr2Si2PO12) that delivers a much higher discharge potential of 3.4 V than other metal-air batteries resulting in high energy density and achieves > 86 % energy efficiency at 0.1 mA cm−2 over 100 cycles. This cell design takes advantage of moisture in ambient air to form an in-situ catholyte via the deliquescent property of NaOH. As a result, not only reversible electrochemical reaction of Na2CO3·xH2O is activated but also its kinetics is facilitated. Our results demonstrate the reversible use of free ambient air as a fuel, enabled by the reversible electrochemical reaction of carbonates with a solid electrolyte.

Strengthening mechanism of red mud with calcium oxide

Currently, the utilization rate of red mud is very low, and the problems of occupying land and polluting the environment are becoming increasingly prominent. This study utilized CaO to prepare Red Mud-based cementitious material (RMC) to achieve clean and efficient utilization of red mud. The mechanism of Ca2+ enhancing the strength of RM and the carbonation reaction in RMC were studied using X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), Thermogravimetric Analysis (TGA), Scanning electron microscopy (SEM) and other analysis methods. The results showed that the carbonization of CaO in RMC bonded the red mud particles and provided early strength. CaO activated the components of gibbsite, diaspore, and silica in RM, and hydration reaction generated gel-like Al-substituted tobermorite (Ca5Si5Al(OH)O17·5 H2O), ensuring the increase of later strength. At the age of 28 days, the RMC with a CaO content of 25% had the highest unconfined compressive strength, reaching 2.19 MPa. When the CaO content exceeded 25%, the compressive strength of RMC gradually decreased. This is due to the reaction of calcium carbonate and aluminate to form a large number of sheets of calcium aluminate monocarbonate (Ca4Al2O6CO3·11 H2O), which weakened the carbonation binding effect and competitively consumed aluminate, resulting in an increase in structural cracks and pores, and a decrease in the compressive strength of RMC.