Tetrabutylammonium Bromide Research Articles

Pyridine vs DABCO vs TBAB in Annulations of δ-Acetoxy Allenoates with Thioamides Leading to Dihydrothiophene, Thiopyran, and Thiazole Scaffolds.

The same δ-acetoxy allenoates and thioamides, under DABCO, pyridine, or tetra-n-butyl ammonium bromide (TBAB) catalysis, undergo distinctly different annulations giving chemoselective routes to dihydrothiophene, thiopyran, or thiazole motifs. Thus, using pyridine in [3 + 2] annulation, dihydrothiophenes are obtained as essentially single diastereomers. By contrast, under DABCO catalysis, allenoates deliver thiopyran motifs in good to high yields through 6-exo-dig cyclization. In the thiazole forming [3 + 2] annulation, tetra-n-butyl ammonium bromide (TBAB) facilitates addition-elimination and 5-exo-trig cyclization in which β- and γ-carbons of allenoates participate to deliver thiazole cores exclusively with a Z-isomeric exocyclic double bond. A possible rationale for these observations is delved into.

Mixtures of choline chloride and tetrabutylammonium bromide with imidazole as examples of deep eutectic solvents: their structure by theoretical and experimental investigation

Imidazole based eutectic solvents have been recently proposed as novel solvents and have been synthetized and characterized by different experimental techniques. We studied the structure of two deep eutectic solvents (DESs) based on imidazole and two organic salts (tetrabutylammonium bromide, TBABr, and choline chloride, ChCl). We focused our attention on the microscopic distribution of their components in the liquids by a study of Infrared and Raman spectroscopy and X-ray diffraction. The vibrational spectra of the eutectic mixtures have been analysed with the aim to characterized the nature of the interactions between anions, cations and imidazole. X-ray diffraction pattern has been interpreted on the light of the intermolecular contacts. Vibrational spectra and diffraction data have been compared with the results of computational studies obtained for both the DESs by molecular dynamics and quantum chemistry calculations.

Amine-Ionic Liquid Blends in CO2 Capture Process for Sustainable Energy and Environment

In the present work, an experiment for CO2 capture process were performed by absorption using various aqueous solvent blends of amine and ionic liquids. The solvent blends were prepared for various compositions by mixing TetraButylAmmonium Acetate [TBA][OAC] and TetraButylAmmonium Bromide [TBA][Br] ionic liquids with Monoethanolamine (MEA). The obtained results were compared with baseline MEA. It was observed that capture efficiency of CO2, absorption rate of CO2 and CO2 diffusion coefficient of MEA-[TBA][OAC] and MEA-[TBA][Br] solvent blends were comparatively higher than baseline 30%MEA. Moreover, the parameters such as density, viscosity, pH, carbon loading and surface tension of all the solvent blends were measured for before and after absorption process. The carbon loading of solvent blends MEA-[TBA][Br] (0.405 mole of CO2/mole of solvent) and MEA-[TBA][OAC](0.459 mole of CO2/mole of solvent) was slightly lower than baseline MEA (0.494 mole of CO2/mole of solvent). However, the viscosity of MEA-[TBA][Br] blends were remarkably lower than MEA-[TBA][OAC] blend and baseline MEA. This might be an important key factor in solvent recovery process with lesser energy demand for sustainable energy and environment.

Influence of TBAB on the Chemical Speciation of Copper(II) Binary Complexes with Biologically Important Ligands, L-Glutamine and Succinic Acid

Influence of tetrabutylammoniumbromide (TBAB) on the chemical speciation of binary complexes of copper (II) with biologically important ligands, L-glutamine, and succinic acid has been studied in varying concentrations (0.0-3.0 %, w/v) of TBAB-water mixtures using a Control Dynamics-APX 175E/C pH meter at an ionic strength of 0.16 mol dm-3 and temperature 303 K. The models for the species of these ligands are refined by using the computer programs SCPHD and MINIQUAD75. Copper(II) active forms are ML, ML2, and ML2H for succinic acid and ML2 and ML2H for L-glutamine. The variation of stability constants with % w/v TBAB is explained based on electrostatic and non-electrostatic forces. The formed species distribution with pH at different solvent compositions and equilibria of the species are reported in the present study. The plausible structures for refined species are also presented.

The Effect of Various Concentrations of Tetra-n-butylammonium Fluoride on the Dissociation Enthalpy of Gas Hydrates

Semiclathrate hydrate formers such as tetra-n-butylammonium bromide (TBAB), chloride (TBAC) and fluoride (TBAF) are promising compounds that mild the thermodynamic conditions of gas hydrates, considerably. The Clausius-Clapeyron equation is employed in this manuscript to calculate the dissociation enthalpies of methane/carbon dioxide/nitrogen + TBAF semiclathrate hydrates. A 460 cm3 stirred batch reactor was used to measure the phase equilibria of gas + TBAF semiclathrate hydrates at various concentrations of tetra-n-butylammonium fluoride. The dissociation P-T data were obtained using an isochoric pressure-search method in the temperature range of 275.15 to 304.7 K and the pressure range of 0.53 to 10.24 MPa at 0.0 - 0.4482 mass fraction of TBAF. Investigating the obtained dissociation data showed that the addition of TBAF to the solution increases the amount of dissociation enthalpy of semiclathrate hydrates per mole of the hydrated gas. Increasing the mass fraction of tetra-n-butylammonium fluoride, showed a straight relation with the amount of dissociation enthalpy per mole of hydrated gas.

Investigations into mechanism and origin of regioselectivity in the metallaphotoredox-catalyzed α-arylation of N-alkylbenzamides.

A mechanistic study on the α-arylation of N-alkylbenzamides catalyzed by a dual nickel/photoredox system using aryl bromides is reported herein. This study elucidates the origins of site-selectivity of the transformation, which is controlled by the generation of a hydrogen atom transfer (HAT) agent by a photocatalyst and bromide ions in solution. Tetrabutylammonium bromide was identified as a crucial additive and source of a potent HAT agent, which led to increases in yields and a lowering of the stoichiometries of the aryl bromide coupling partner. NMR titration experiments and Stern–Volmer quenching studies provide evidence for complexation to and oxidation of bromide by the photocatalyst, while elementary steps involving deprotonation of the N-alkylbenzamide or 1,5-HAT were ruled out through mechanistic probes and kinetic isotope effect analysis. This study serves as a valuable tool to better understand the α-arylation of N-alkylbenzamides, and has broader implications in halide-mediated C–H functionalization reactions.

Tetrabutylammonium bromide-based hydrophobic deep eutectic solvent for the extraction and separation of dihydromyricetin from vine tea and its inhibitory efficiency against xanthine oxidase.

In this study, deep eutectic solvent oscillation-assisted extraction (DES-OS) combined with macroporous resin adsorption and desorption technology was used to achieve the rapid green extraction and separation of the characteristic component dihydromyricetin (DMY) from vine tea. Multivariate data analysis showed that the DES system composed of tetrabutylammonium bromide (N444Br) and pyruvic acid (molar ratio 1 : 2) had good extraction performance for DMY. The influence parameters of DES-OS were studied, and optimized by the single-factor test and response surface methodology (RSM) with Box-Behnken design (BBD). The extraction model of DMY was established and verified. The results showed that the extraction yield of DMY could reach 40.1 mg g-1 under the optimal conditions (DES water contents of 71.18%, extraction time of 2.80 h, extraction temperature of 46.40 °C), which is in good agreement with the predicted value. In addition, Fourier transform infrared spectroscopy (FT-IR) was used to characterize the solvent before and after extraction. Scanning electron microscopy (SEM) results further confirmed that tetrabutylammonium bromide:pyruvate enhanced the destruction of the cell wall structure, resulting in the release of more DMY. Furthermore, different macroporous resins were selected for the separation of DMY for the DES-OS extract, and it was found that the DM301 resin had the ideal recovery performance under optimized dynamic condition. Finally, the product was found to have an inhibitory effect against xanthine oxidase (XO) as a mixed-type competitive inhibitor with IC50 values of (5.79 ± 0.22) × 10-5 mol L-1. The inhibitory mechanisms of DMY on XO were explored by enzyme kinetics, spectroscopy, molecular docking and molecular dynamics analysis approaches, which provided a theoretical basis for the above inhibition assays.

The possibility of using DES based on polypropylene glycol 425 and tetrabuthylammonium bromide in the extraction processes of transition metals

Traditionally, the method of liquid extraction is used to extract metals from aqueous. This work is devoted to the combination of perspective alternative for hazardous solvents (aqueous two-phase systems based on water-soluble polymers) and the novel deep eutectic solvents in the non-ferrous metals extraction processes. In this work, the synthesis of deep eutectic solvent based on a water-soluble polymer (PPG-425) and tetrabutylammonium bromide (TBAB) by stirring for 10 minutes at 80° C has been shown. The obtained results showed not only the possibility of using DES in the metal extraction process, but the selectivity to the Fe(III) and Zn(III), the distribution coefficients were 71.64 and 25.17 respectively. The metal concentrations were determined spectrophotometrically using 4-(2-pyridylazo)resorcinol. This work shows the perspectives of using DESs in the metal extraction processes.

Effect of TBAB on the Chemical Speciation of Complexes of Zinc(II) with L-Glutamine and Succinic Acid

Effect of Tetrabutylammoniumbromide (TBAB) on the chemical speciation of binary complexes of Zinc(II) with L-glutamine and succinic acid has been studied pH metrically in varying concentrations (0.0-3.0 %, w/v) of TBAB-water mixtures. The temperature and the ionic strength maintained in the titrant are 0.16 mol dm-3 and 303 K, respectively. The possible models that represent the title systems are refined by using the computer programs SCPHD and MINIQUAD75. The models contain ML and MLH for succinic acid and ML2 and ML2H for L-glutamine complexes of Zinc(II). The variation of the stability constants with a dielectric constant is explained based on electrostatic and non-electrostatic forces. The species distribution with pH at different solvent compositions, corresponding chemical equilibria, and structures of the complex species are described.

A chromatographic approach for studying the adsorption of polar small molecules on tetrabutylammonium bromide semiclathrate hydrate.

A new liquid chromatography system in which tetrabutylammonium bromide semiclathrate hydrate (TBAB-SCH) was used as the column-packing material is proposed to evaluate the adsorption mechanisms of polar small molecules on a TBAB-SCH surface. It has been revealed that the more hydrophilic molecules tend to be more strongly retained on the TBAB-SCH/hexane-diethyl ether interface, and the retentions of aromatics (ARs) and crown ethers (CEs) are differently controlled. CEs are likely retained on the TBAB-SCH interface via hydrogen-bond formation as well on water-ice, whereas the retention mechanism of ARs is unique to TBAB-SCH and has not previously been observed on water-ice. This difference between CEs and ARs may arise from differences in the types of polar groups or molecular size. This chromatographic approach will provide useful information for evaluating the adsorption mechanisms of inhibitors for clathrate hydrate agglomeration, which is a common agglomeration problem experienced by industries.

Ti and Zr amino-tris(phenolate) catalysts for the synthesis of cyclic carbonates from CO2 and epoxides

Herein, we report the application of four amino-tris(phenolate)-based metal complexes incorporating Ti(IV) or Zr(IV) centres (2a-3b) as homogeneous catalysts for the conversion of CO2 and epoxides into cyclic carbonates. The four complexes were synthesised, characterised and then evaluated in combination with tetrabutylammonium iodide, bromide or chloride as binary catalytic systems for the reaction of CO2 with 1,2-epoxyhexane as epoxide substrate at 12 bar CO2 pressure and 90 °C for 2 h. The catalytic systems comprising the two Ti(IV) complexes (2a and 2b) showed similar performance. One notable exception was the catalytic system consisting of titanium complex 2b, bearing an axial Cl-ligand, and tetrabutylammonium chloride, which displayed higher catalytic activity compared to other titanium-based systems. Even higher activity was achieved with Zr(IV) complex 3a, bearing an axial isopropoxide ligand, which reached turnover numbers (TONmetal) up to 1920 for the reaction of CO2 with 1,2-epoxyhexane at 12 bar CO2 pressure and 90 °C for 2 h. This performance is comparable with that of state-of-the-art catalysts for this reaction. The catalytic system consisting of complex 3a and tetrabutylammonium bromide was explored further by investigating its applicability with a broad substrate scope, achieving quantitative conversion of several epoxides with CO2 into cyclic carbonate products at 90 °C and 12 bar CO2 pressure for 18 h. The selectivity towards the cyclic carbonate products was ≥ 98% for all studied terminal epoxides and ≥ 80% for all examined cyclohexene-type epoxides.

Regiodivergent Conversion of Alkenes to Branched or Linear Alkylpyridines.

Herein we report a practical protocol for the visible-light-induced regiodivergent radical hydropyridylation of unactivated alkenes using pyridinium salts. This approach provides a unified synthetic platform to control the regioselectivity of the synthesis of linear or branched C4-alkylated pyridines. A remarkable selectivity switch from the anti-Markovnikov to the Markovnikov product can be achieved by the addition of tetrabutylammonium bromide. The versatility of this protocol is further demonstrated based on the late-stage functionalization in pharmaceuticals.

An electrical resistivity-based method for measuring semi-clathrate hydrate formation kinetics: Application for cold storage and transport

Tetra-n-butylammonium bromide (TBAB) semi-clathrate hydrate has a large latent heat and suitable phase transition temperatures to be used as a phase change material for cold energy storage and transport. The mass fraction of hydrates in the semi-clathrate hydrate slurry is a key parameter determining the cold carrying capacity and flow properties. We developed a new experimental methodology based on electrical resistivity to quantify the hydrate fraction in semi-clathrate hydrate slurry during hydrate formation. Relationship between electrical resistivity and hydrate fraction of semi-clathrate hydrate slurry was established based on Bruggeman’s effective-medium approximation. After validation, this method was employed to quantitatively investigate the effect of temperature on TBAB hydrate formation from 20 wt% TBAB/water system. As the temperature was lowered from 278.2 K to 274.2 K, the induction time was reduced by 97.8% and the hydrate growth rate was enhanced by over 2.5 times. At 274.2 K and 276.2 K, type A hydrates were preferentially formed followed by a structural transition to type B. At 278.2 K, only type A hydrates were observed. Furthermore, given an appropriate concentration, amino acid L-tryptophan was identified to be a good kinetic promoter for TBAB hydrate formation. The presence of 500 ppm L-tryptophan reduced the induction time by 60% and boost the hydrate growth rate by more than 32%. The electrical resistivity-based method developed in this work has shown simplicity, low cost, high accuracy, and repeatability. It would enable precise investigation of semi-clathrate hydrate kinetics in the future for cold energy applications and beyond.

Green synthesis of benzaldehydes by the selective oxidation o benzyl alcohols using hexacyanoferrate (III) and bromate under phase transfer catalysis

The selective oxidation of benzyl alcohols and substituted benzyl alcohols was carried out in greener solvents like ethyl acetate and toluene by hexacyanoferrate (III) and bromate ions under phase transfer catalysis. Various phase transfer catalysts like tetrabutylphosphonium bromide, tetrabutylammonium bromide, tetrabutylammonium hydrogen sulphate, cetyltrimethylammonium bromide and tricaprylmethylmmonium chloride were used. A pinch of sodium tungstate dihydrate is added as a co-catalyst when bromate is used an oxidant and hexacyanoferrate (III) is used in presence of mineral acids. The products obtained were precipitated as their 2,4- dinitrophenylhydrazone, purified, weighed and the yield was found to be > 90 %. The products were recrystallized in ethanol and analyzed by melting point and by various spectral techniques. It was proved that corresponding benzaldehydes were formed and there was no further oxidation to corresponding acids. All the catalysts were found effective in bringing out the reaction but based on yield and ease of reaction, the order of reactivity is tricaprylmethylammonium chloride > tetrabutylphosphonium bromide > tetrabutylammonium bromide > tetrabutylammonium hydrogen sulphate > cetyltrimethylammonium bromide. The selective oxidation of benzyl alcohols is very difficult to proceed in organic solvents without the aid of a phase transfer catalyst. Yield of products is found to be slightly more in ethyl acetate than that in toluene due to difference in polarity.

New chloroacetic acid-based deep eutectic solvents for solubilizing metal oxides

In this work, new chloroacetic acid-based deep eutectic solvents (DESs) were prepared from the tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide, and tetrabutylammonium hydrogen sulfate as a hydrogen bond acceptors (HBAs) in combination with chloroacetic acid as a hydrogen bond donor (HBD). The prepared deep eutectic solvents were characterized by measuring their physical properties such as density, sound velocity, electrical conductivity, viscosity, refractive index, and surface tension with the variation of temperature. The new deep eutectic solvent was applied for solubilizing Fe3O4, CuO, ZnO, and PbO metal oxides. The obtained solubilizing data was compared with the other deep eutectic solvent based on the different hydrogen bond donors and acceptors which were used for the solubility of metal oxides.

Synergistic stabilization of CsPbI3 inorganic perovskite via 1D capping and secondary growth

Cesium lead iodide (CsPbI3) perovskite has gained great attention in the photovoltaic (PV) community because of its unique optoelectronic properties, good chemical stability and appropriate bandgap for sunlight harvesting applications. However, compared to solar cells fabricated from organic-inorganic hybrid perovskites, the commercialization of devices based on all-inorganic CsPbI3 perovskites still faces many challenges regarding PV performance and long-term stability. In this work, we discovered that tetrabutylammonium bromide (TBABr) post-treatment to CsPbI3 perovskite films could achieve synergistic stabilization with both TBA+ cation intercalation and Br-doping. Such TBA+ cation intercalation leads to one-dimensional capping with TBAPbI3 perovskite formed in situ, while the Br-induced crystal secondary growth helps effectively passivate the defects of CsPbI3 perovskite, thus enhancing the stability. In addition, the incorporation of TBABr can improve energy-level alignment and reduce interfacial charge recombination loss for better device performance. Finally, the highly stable TBABr-treated CsPbI3-based perovskite solar cells show reproducible photovoltaic performance with a champion efficiency up to 19.04%, while retaining 90% of the initial efficiency after 500 h storage without encapsulation.

Synthesis of a new hybrid nanocomposite based on vanadium (V) substituted Keggin-type polyoxometalate and polyvinyl alcohol ((TBA)4PMo10V2@PVA) as a nanocatalyst for germination of barley seeds

To investigate a new nanocomposite based on vanadium(V) substituted Keggin-type polyoxometalate as a new nanocatalyst on barley seed germination, nanocomposite (TBA)4PMo10V2@PVA was prepared by reaction of H5PMo10V2O40, tetrabutylammonium bromide (TBA), and polyvinyl alcohol (PVA) at room temperature via sol-gel method. The synthesized hybrid nanocomposite was characterized by FT-IR, UV-vis, XRD, SEM and 31P NMR spectroscopy. The influence of the new organic-inorganic hybrid nanocomposite TBA-PMo10V2@PVA was investigated in germination of barley seeds. In order to compare, several types of polyoxometalates with different concentrations were used to study their effects on growth factors of barley seeds. The obtained results indicate that using ((TBA)4PMo10V2@PVA) with 10 and 100 µM concentrations achieved the most preferred results.

Hydrate Phase Equilibria of Ternary Gas Mixtures with Tetrabutylammonium Bromide and Cyclopentane

Hydrate Phase Equilibria of Ternary Gas Mixtures with Tetrabutylammonium Bromide and Cyclopentane

Quaternary Ammonium-Mediated Delamination of Europium-Based Metal-Organic Framework into Ultrathin Nanosheets for the Selective Photoelectrochemical Sensing of Fe3.

Structural delamination of bulk layered metal-organic frameworks (MOFs) remains a great challenge, largely owing to a lack of general synthetic strategies. Here, we reported a simple solvent-free intercalation strategy for the delamination of rare-earth-based MOF (RE-MOF) with a topology structure of MIL-78 by tuning the chain length of quaternary ammonium salts. Four types of quaternary ammonium salts, involving tetraethylammonium bromide (TEAB), tetrapropylammonium bromide (TPAB), tetrabutylammonium bromide (TBAB), and hexadecyl trimethyl ammonium bromide (CTAB) were introduced to investigate their intercalation capabilities. It is evident in our case that the interruption/intercalation behavior of quaternary ammonium salts differs with their steric structures, and the chain-like CTAB can induce obvious delamination of MIL-78 crystals. Particularly, the CTAB-intercalated ultrathin Eu-based MIL-78 nanosheets exhibited unique selective photoelectrochemical sensing property toward trace amounts of Fe3+ ions in aqueous solution with a detection limit of 0.0899 μM at a signal-to-noise ratio of 3. These results demonstrated a green bottom-up strategy to obtain high-quality RE-MOF nanosheets for potential photocurrent response applications.

Effect of monomer hydrophilicity on ARGET–ATRP kinetics in aqueous mini‐emulsion polymerization

AbstractActivators regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP)‐based aqueous miniemulsion polymerization where the polymerization takes place in the stabilized monomer droplets is described. In this work, we compared styrene, n‐butyl methacrylate (nBMA) and tert‐butyl methacrylate (tBMA) and investigated the influence of their hydrophobicity on dispersity, molecular weight and particle stability based their partition coefficients (logP) (2.67, 2.23, and 1.86, respectively). Tetrabutylammonium bromide (TBAB) was used as a phase transfer agent for the controlled delivery of Cu2+‐Br/tris(2‐pyridylmethyl)amine (TPMA), a hydrophilic catalyst, into monomer droplets of varying hydrophobicity. The resulting dispersity and particle stability of each polymer is a function of its logP value, with the most hydrophobic monomer (styrene) displaying the narrowest dispersity and most control (Đ < 1.3), and the most hydrophilic polymer poly(tert‐butyl methacrylate) (PtBMA) having reduced emulsion stability, determined by the observation of aggregate formation. Selected polymerization parameters, including effects of total ascorbic acid feed concentration and the monomer concentration and their effects on dispersity are reported. The controlled polymerizations of hydrophilic monomers using ARGET‐ATRP in miniemulsion conditions and understanding the effect of monomer hydrophilicity on the emulsion stability will broaden the use of ARGET‐ATRP in emulsion polymerization for the synthesis of polymer‐grafted nanoparticles with hydrophilic corona.