Reaction Of Carbonate Research Articles

Theoretical investigation toward organophosphine‐catalyzed [3 + 3] annulation of Morita–Baylis–Hillman carbonates with azomethine imines: Mechanism, origin of stereoselectivity, and role of catalyst

AbstractA computational study on the detailed mechanism and stereoselectivity of the chiral phosphine‐catalyzed C(sp2)H activation/[3 + 3] annulation between Morita–Baylis–Hillman (MBH) carbonates and C,N‐cyclic azomethine imines has been performed. Generally, the catalytic cycle consists of two stages, that is, C(sp2)H activation companied by the dissociation of the t‐BuO group forming phosphonium enolate, and [3 + 3] cycloaddition process followed by regeneration of the catalyst. The calculated results indicate that C(sp2)H activation is rate‐determining while [3 + 3] cycloaddition is stereoselectivity‐determining. Furthermore, the advantageous hydrogen bond interactions and less steric hindrance in the RR configurational CC bond forming transition states should be responsible for the favorability of RR‐configured product among the four possible products. The special role of the organocatalyst was also identified by natural bond orbital (NBO) and global reactivity index (GRI) analyses. The mechanistic insights obtained in the present study should be useful for understanding the novel organocatalytic C(sp2)H activation and cycloaddition cascade reaction of MBH carbonates, and thus provide valuable clues on rational design of efficient organocatalysts for the C(sp2)H activation/functionalizations.

Assessing the chemical involvement of limestone powder in sodium carbonate activated slag

This study aims to investigate the effect of limestone powder (LP) on the reaction of sodium carbonate activated slag. The results show that the incorporated LP up to 30% improves the strength development, especially at advanced curing ages. A slightly accelerated reaction is observed for samples containing low amount of LP (≤5%), while mixture with 10% LP shows the optimized results with respect to the heat release and strength development. Chemical effect of incorporating LP is observed at high replacement levels (≥15%), indicated by the formation of a new phase, natron (Na2CO3·10H2O). Besides, relatively high contents of hydrotalcite-like phases are generated when increasing the dosage of limestone powder. The chemical changes, including the volume changes of generating natron and the transformation of natron to calcite, is potentially responsible for the enhanced mechanical properties.

Carbon-carbon bond formation catalyzed by PEPPSI Pd-NHC

Five new palladium complexes were efficiently synthesized from the reaction of benzimidazolium salts, potassium carbonate (K2CO3) and palladium chloride (PdCl2) in pyridine (for 3–5) or 3-chloropyridine (for 6 and 7). The synthesized complexes were characterized and tested in Suzuki-Miyaura cross-coupling reaction as catalysts. In the presence of catalysts 3–7, biaryl products were obtained in moderate yields when phenylboronic acid was used as boronic acid derivative. However, the coupling of thianaphthene-2-boronic acid with 1-chloro-4-nitrobenzene generated low yields although a longer period of time was used in comparison to the coupling of phenylboronic acid with aryl chlorides.

Thermogravimetric and kinetic analysis of thermal decomposition characteristics of microbial calcites induced by cyanobacteria Synechocystis sp. PCC6803

Although various complicated methods have always been made attempts, it is still well difficult to efficiently distinguish between the biogenic and abiogenic minerals in geological area up to now. In present study, the thermal decomposition unique characteristics of microbial calcites (MC), induced by cyanobacteria Synechocystis sp. PCC6803, were compared with those of chemical calcites (CC) prepared by the reaction of sodium carbonate (Na2CO3) with calcium chloride (CaCl2). Two samples were firstly analyzed by scanning electron microscope and X-ray diffraction, and were further investigated thermal decomposition behaviors using a thermogravimetric analyzer at different heating rates of 278.15, 283.15, 293.15, and 303.15 K min−1 from 323.15 to 1273.15 K, respectively, then kinetic parameters were calculated via Popescu, Kissinger–Akahira–Sunose, and Flynn–Wall–Ozawa methods, and then the kinetics mechanism functions were deduced by Popescu method. The results showed that these two kinds of precipitates were actually both calcite crystals although the surface morphologies were quite different. Whereas thermal decomposition kinetics mechanism function of MC can be described as Avrami–Erofeev equation ([−ln(1 − α)]1/3), while CC corresponded to Contracting sphere (volume) ([1 − (1 − α)]1/3), the results also showed that the average activation energy of MC and CC was 217.9 and 170.5 kJ mol−1, respectively; that is, MC has higher thermal stability, which should be originated from the inducing effects and the different precipitation conditions provided by Synechocystis sp. PCC6803. These above results provided useful information not only for efficiently distinguishing between the biogenic and abiogenic minerals in geological area, and also for better understanding the microbial mineralization.

An efficient synthesis of 3,4-dihydropyrimidin-2(1H)-one and 5,6-diphenylpyrimidine derivatives under solvent-free and base conditions

An efficient and convenient Biginelli-like reaction one-pot synthesis of a series of 4-aryl-5,6-diphenyl-3,4-dihydropyrimidin-2(1H)-one and 4-aryl-5,6-diphenylpyrimidine derivatives under solvent-free conditions from the reaction of aromatic aldehydes, 1,2-diphenylethanone, urea, guanidine carbonate or acetamidine hydrochloride has been reported. This methodology has the advantages of short reaction time, mild reaction conditions, easy work-up and environmental friendliness. Moreover, 4-aryl-5,6-diphenylpyrimidine derivatives were first reported in this process. The structures of the title compounds were further determined by X-ray diffraction. More importantly, different from general Biginelli reaction, this reported method was carried out under base conditions.

A combined high-temperature experimental and theoretical kinetic study of the reaction of dimethyl carbonate with OH radicals.

The reaction kinetics of dimethyl carbonate (DMC) and OH radicals were investigated behind reflected shock waves over the temperature range of 872-1295 K and at pressures near 1.5 atm. Reaction progress was monitored by detecting OH radicals at 306.69 nm using a UV laser absorption technique. The rate coefficients for the reaction of DMC with OH radicals were extracted using a detailed kinetic model developed by Glaude et al. (Proc. Combust. Inst. 2005, 30(1), 1111-1118). The experimental rate coefficients can be expressed in Arrhenius form as: kexpt'l = 5.15 × 1013 exp(-2710.2/T) cm3 mol-1 s-1. To explore the detailed chemistry of the DMC + OH reaction system, theoretical kinetic analyses were performed using high-level ab initio and master equation/Rice-Ramsperger-Kassel-Marcus (ME/RRKM) calculations. Geometry optimization and frequency calculations were carried out at the second-order Møller-Plesset (MP2) perturbation level of theory using Dunning's augmented correlation consistent-polarized valence double-ζ basis set (aug-cc-pVDZ). The energy was extrapolated to the complete basis set using single point calculations performed at the CCSD(T)/cc-pVXZ (where X = D, T) level of theory. For comparison purposes, additional ab initio calculations were also carried out using composite methods such as CBS-QB3, CBS-APNO, G3 and G4. Our calculations revealed that the H-abstraction reaction of DMC by OH radicals proceeds via an addition elimination mechanism in an overall exothermic process, eventually forming dimethyl carbonate radicals and H2O. Theoretical rate coefficients were found to be in excellent agreement with those determined experimentally. Rate coefficients for the DMC + OH reaction were combined with literature rate coefficients of four straight chain methyl ester + OH reactions to extract site-specific rates of H-abstraction from methyl esters by OH radicals.

Ecological indices of manufacture of Portland cement clinker and production of the dolomite clinker

It is shown that the production of dolomite clinker in comparison with that of Portland cement is environmentally appropriate. When calcining dolomite for cementitious binder, the pollution of the atmosphere by carbon dioxide is reduced due to its isolation during decarbonization reactions of calcium carbonates. Reducing fuel consumption for clinker burning provides less carbon dioxide emissions from combustion products. Reducing the firing temperature creates obstacles to the formation of nitrogen oxides. The production of binders from dolomite in comparison with the production of Portland cement helps to protect the environment from contamination

Alkali metal ion catalysis and inhibition in alkaline ethanolysis of O-Y-substituted-phenyl O-phenyl thionocarbonates: contrasting M+ ion effects upon changing electrophilic centre from C=O to C=S

Pseudo-first-order rate constants (kobsd) were measured for nucleophilic substitution reactions of O-Y-substituted-phenyl O-phenyl thionocarbonates (4a–4h) with alkali metal ethoxides (EtOM, M = Li, Na, or K) in anhydrous ethanol at 25.0 ± 0.1 °C. Plots of kobsd vs. [EtOM] exhibited upward curvature for the reaction of O-4-nitrophenyl O-phenyl thionocarbonate (4a) with EtOK in the presence of 18-crown-6-ether (18C6), but showed downward curvature for the reaction with EtOLi, indicating that the reaction is catalyzed by the 18C6-crowned K+ ion, but is inhibited by Li+ ion. The kobsd values were dissected into kEtO− and kEtOM, the second-order rate constant for the reaction with dissociated EtO− and ion-paired EtOM, respectively. The reactivity of EtOM toward 4a increases in the order EtOLi < EtONa < EtO− < EtOK < EtOK/18C6, which is in contrast to that reported previously for the corresponding reaction of 4-nitrophenyl phenyl carbonate (a C=O analogue of 4a), e.g., EtO− ≈ EtOK/18C6 < EtOLi < EtONa < EtOK. The reaction mechanism, including the transition-state model and the origin of the contrasting reactivity patterns found for the reactions of the C=O and C=S compounds, are discussed.

A facile synthesis of sulfonylureas via water assisted preparation of carbamates.

A novel and simple approach to the synthesis of sulfonylureas has been reported. It involved the reaction of various amines with diphenyl carbonate to yield the corresponding carbamates, which subsequently reacted with different sulphonamides to produce different sulfonylureas in excellent yields. The first reaction of diphenyl carbonate with amines was carried out in aqueous : organic (H2O : THF, 90 : 10) medium at room temperature to produce carbamates that paved a straightforward route to sulfonylureas after reaction with sulfonamides. The above process avoided traditional multistep protocols and the use of hazardous, irritant, toxic and moisture sensitive reagents such as phosgene, isocyanates and/or chloroformates.

Low-temperature stages in the mechanochemical synthesis of gamma-lithium monoaluminate

Low-temperature (<500°C) stages in the synthesis of gamma-lithium monoaluminate through heat treatment of a mechanically activated mixture of aluminum hydroxide and lithium carbonate have been studied by thermogravimetry and differential scanning calorimetry in combination with mass spectrometry. The results demonstrate that heating the mixture to above 80–100°C is accompanied by the release of not only water (resulting from the decomposition of X-ray amorphous aluminum hydroxide) but also carbon dioxide. The carbon dioxide originates from the reaction of the lithium carbonate with the products of X-ray amorphous aluminum hydroxide thermolysis.

Well‐Defined Cesium Benzotriazolide as an Active Catalyst for Generating Disubstituted Ureas from Carbon Dioxide and Amines

AbstractThe reaction of alkali metal carbonates with various azole compounds produced a new series of alkali metal azolides, and they were applied as active catalysts for the production of disubstituted ureas from the carboxylation of various amines with CO2. Among them, cesium benzotriazolide (Cs[BTd]) was found to be the most active for the carboxylation reaction and was structurally characterized by single‐crystal X‐ray diffraction. The crystal structure of highly hygroscopic Cs[BTd] was found to be [BTA]⋅⋅⋅Cs[BTd], which explains why it is a water‐tolerant active species for this carboxylation reaction, leading to a maximum turnover frequency of 344 h−1 as well as high recyclability even after five successive runs.

Palladium-Catalyzed Three-Component Reaction of Propargyl Carbonates, Isocyanides, and Alcohols or Water: Switchable Synthesis of Pyrroles and Its Bicyclic Analogues.

In the presence of a catalytic amount of Pd(OAc)2 and a stoichiometric amount of tert-butylamine, the reaction of propargyl carbonates, isocyanides, and alcohols afforded polysubstituted aminopyrroles in good yields. Using water as a nucleophile instead of alcohol, the same reaction provided 1,4-dihydro-6H-furo[3,4-b]pyrrol-6-imines. A triple isocyanide insertion to the hypothetic (σ-allenyl)palladium(II) intermediate was involved in these ABC3-type multicomponent reactions. The key role of tert-butylamine was accounted for by its reaction with in situ generated carbon dioxide to form the carbamic acid, which in turn served as a nucleophile to trap the nitrilium intermediate.

A new class of non-isocyanate urethane methacrylates for the urethane latexes

A series of new urethane methacrylate (UMA) monomers were synthesized with the reaction of ethylene carbonate and aliphatic amines, followed by the reaction with methacrylic anhydride. The monomers were characterized by 1H, 13C nuclear magnetic resonance (NMR), mass (MS), and Fourier transform infrared (FTIR) spectroscopies. Urethane latexes were prepared by monomer-starved semibatch polymerization of the new urethane methacrylates with methyl methacrylate (MMA) and butyl acrylate (BA). A uniform morphology and a unimodal particle distribution were observed by a combination of dynamic light scattering (DLS), ultrasound acoustic attenuation spectroscopy (UAAS), and transmission electron microscopy (TEM). The thermal stability, minimum film formation temperature (MFFT) and thermo-mechanical properties of the urethane latexes were also studied. The inclusion of urethane monomers appeared to have lowered the MFFT via a water plasticization effect, while enhancing the Tg of the final film properties.

Reductive Decomposition Reactions of Ethylene Carbonate by Explicit Electron Transfer from Lithium: An eReaxFF Molecular Dynamics Study

A detailed understanding of the mechanism of the formation of the solid electrolyte interphase (SEI) is crucial for designing high-capacity and longer-lifecycle lithium-ion batteries. The anode-side SEI primarily consists of the reductive dissociation products of the electrolyte molecules. Any accurate computational method for studying the reductive decomposition mechanism of electrolyte molecules is required to include an explicit electronic degree of freedom. In this study, we employed our newly developed eReaxFF method to investigate the major reduction reaction pathways of SEI formation with ethylene carbonate (EC) based electrolytes. In the eReaxFF method, electrons are treated explicitly in a pseudoclassical manner. The method has the ability to simulate explicit electrons in a complex reactive environment. Our eReaxFF-predicted results for the EC decomposition reactions are in good agreement with the quantum chemistry data available in the literature. Our molecular dynamics (MD) simulations capture...

Synthesis and radical polymerization of styrene bearing 2-oxazolidone moiety derived from α-amino acid and investigation of its phenol adsorption behavior

We describe the synthesis and radical polymerization of series of styrenes with 2-oxazolidone moieties inherited from α-amino acids on the side chain. The 2-oxazolidone 2 was readily synthesized through the reaction of diphenyl carbonate with amino alcohols 1 that were prepared through the reduction of the corresponding α-amino acids (glycine, l-alanine, l-phenylalanine, l-valine, and l-methionine), in the presence of 1,8-diazabicyclo[5.4.0]-7-undecene as a base catalyst. The subsequent N-substitution reaction of 2-oxazolidone with 4-(chloromethyl) styrene in the presence of sodium hydride produced high yield of the corresponding styrenic compounds 3. Free radical polymerization of these monomers 3 smoothly proceeded in the quantitative monomer-conversion using benzoyl peroxide as a radical initiator to give the corresponding polymers (P3). The thermal properties of the resulting polymers were evaluated by differential scanning calorimetry and thermogravimetric analysis. These oxazolidone-containing polymers effectively adsorbed phenols from aqueous solution, and were also miscible with poly(4-vinylphenol) in the equimolar ratio mixture, because of the effective hydrogen bond interaction involving a carboxyl group of oxazolidone moieties and a hydroxyl group of the phenol.

The effect of glycine on the growth of calcium carbonate in alkaline silica gel

Calcium carbonate was crystallized in alkaline silica gel with the presence of glycine. The crystallization proceeded with a counterdiffusion method by the reaction of calcium chloride and sodium carbonate. Optical microscopy observation showed a significant effect of glycine on the morphology control of calcite crystals. When the initial concentration of glycine was high enough (10mg/mL, 20mg/mL), spherical vaterite particles formed in alkaline silica gel concomitantly together with dumbbell shaped calcite particles. The in situ study by micro-Raman spectroscopy demonstrated that both vaterite and the concomitant calcite were stable phases during their growth processes since the initial appearance. A possible mechanism has been discussed to emphasize the effect of glycine on the nucleation of vaterite and the morphological control of calcite.

Palladium-Catalyzed Multicomponent Reaction (MCR) of Propargylic Carbonates with Isocyanides.

A palladium-catalyzed multicomponent reaction (MCR) of propargylic carbonates with isocyanides is reported. Remarkably, the orderly insertion of isocyanides affords two types of valuable N-heterocyclic products (Z)-6-imino-4,6-dihydro-1H-furo[3,4-b]pyrrol-2-amines and (E)-5-iminopyrrolones in high yields. Systematic analysis of the reaction conditions indicates that the selectivity of these N-heterocyclic products can be controlled by ligands and temperature.

Development of epoxy-urethane hybrid coatings via non-isocyanate route

Non-isocyanate route of urethane synthesis based on reaction of cyclic carbonated compound with amines is well known. Taking inspiration from this, we have synthesized a monomer containing urethane linkage through the reaction of propylene carbonate with ethylene diamine. This monomer was further reacted with commercial epoxy polymer to obtain hybrid epoxy-urethane adduct. Synthesized adduct was then cured with various structural amines such as isophorone diamine (IPDA), Jeffamine T-403 and diaminodiphenyl methane (DDM). The resultant epoxy-urethane hybrid coatings were characterized for mechanical, chemical, thermal and anticorrosive properties. The hybrid coatings exhibited at par mechanical, chemical and corrosion resistance as compared to that of commercial epoxy coatings. DSC and TGA analysis revealed that glass transition temperature, thermal stability and char yield of hybrid coatings was higher than that of commercial epoxy coatings.

Characterization of Dolomitic Lime as the Base Reagent for Precipitation of Mg(OH)2 from Seawater

The process of obtaining magnesium hydroxide from seawater involves precipitation of magnesium ions with suitable basic reagents, such as calcined dolomite. The purity of the magnesium hydroxide precipitate depends on dolomite characteristics; therefore, it is necessary to find high purity dolomite with good physical properties. The aim of this study was to characterize the specific dolomite from the location of Đipalo-Sinj (Croatia), its quality, and the favourable conditions for calcination. Certain physical and chemical characteristics were determined by pure chemical analysis, as well as by using TG/DTG-DTA, FTIR and SEM/EDS analysis. Good chemical quality of dolomitic lime (59.03 wt. % CaO, and 40.69 wt. % MgO) with low content of impurities was confirmed with the TG/DTG-DTA thermal analysis. In the atmosphere of air + CO 2 , dolomite decomposes to CaCO 3 and MgO in a temperature area between 415 and 824 °C; thereafter, another reaction begins – the decomposition reaction of calcium carbonate, completed at 897 °C. In air, the simultaneous decomposition of two carbonates occurs between 657 – 840 °C. The FTIR and EDS analyses confirmed the complete breakdown of carbonates at 950 °C. The main components (Mg, Ca, and O) confirmed the purity of the dolomite lime.

CO Gas Production by CO2 Gas Decomposition in Molten Salt Electrolysis

If CO2 gas can be efficiently decomposed, the produced carbon can be used as the raw material of the reducing agent of iron ore. Oxygen can be also used as the blowing gas into converters. In addition, CO gas can be used as an effective fuel in industrial plants. Thus, all the products arising from CO2 decomposition can become raw materials or energy resources. The decomposition of CO2 gas to carbon or CO gas by electrolysis is examined via the use of a combination of CaCl2-CaO melt as a media and ZrO2 solid-state electrolyte as anode. The schematic of the reactor used in this study is shown in Figure. CO2 gas is injected through the cathodic pipe, and it is reduced near the cathode by metallic Ca that is electrochemically deposited from CaO, leading to formation of carbon or CO gas. However, CO2 gas partially dissolves to form CO3 2- with coexistence of CaO in the melt. CO3 2- precipitates carbon on the cathode. A part of carbon reacts with the blown CO2 gas to form CO gas. These two mechanisms work for effective CO2 decomposition. The anode contained 8 mol% Y2O3 to ensure stability of the ZrO2 cubic crystal structure. By means of utilizing platinum paste as the conductor inside the ZrO2 tube instead of carbon powder, its tube can work as a good anode, and a large amount of CO gas is stably produced in the exhaust gas. At a higher electrolysis temperature, CO2 gas is preferentially converted to CO gas. At 1273 K, the conversion ratio approached the maximum value of 88.2%. The highest concentration of CO gas is generated by application of a cell voltage of 2.55 V, which is lower than the theoretical decomposition voltage of CaO, E 0 CaO (2.65 V at 1173 K). Therefore, CO2 gas decomposes preferentially via the decomposition reaction of carbonate ions.We believe that our approach can contribute in reducing atmospheric CO2. Figure 1