Tetrabutylammonium Acetate Research Articles

Surface tension of aqueous solutions of large organic salts: Tetrabutylammonium acetate solutions

Aqueous solutions of simple ionic salts such as NaCl and NaBr have higher surface tensions compared to that of pure water and the surface tension of the solution increases with the increasing concentration of the salt. In contrast, the aqueous solutions of the ion sodium acetate (NaAc), which has an anion with both hydrophilic and hydrophobic parts, have a surface tension less than that of pure water, with the surface tension decreasing with salt concentration. The presence of large cations in the salt may change these trends. In this work, the interfacial tension of aqueous solutions of the organic ionic salt tetrabutylammonium acetate (TBAAc) is measured and compared with that of tetrabutylammonium bromide (TBAB). The surface tension of TBAAc aqueous solutions with mole fractions ranging from 0.00417 to 0.04191 were measured for temperatures ranging from 288.2 to 308.2 K and compared with the surface tension of TBAB solutions at similar concentrations. The experimental results showed that the interfacial tensions of TBAAc and TBAB aqueous solutions decreased with increasing concentration, leveling at around 0.04 mol fraction. At each concentration, the interfacial tensions of the TBAAc solutions were larger than those of the TBAB solutions. For the TBAAc and TBAB solutions, the surface excess concentrations of the salts in the solutions are calculated. The impact of these results structures and properties of these solutions are discussed.

Selective Palladium(II)‐Catalyzed Dimerization of Styrenes and Acrylates in Molten Tetrabutylammonium Acetate as an Ionic Liquid

AbstractA method for the selective dimerization of styrenes and acrylates has been developed. The reaction is catalyzed by a very low amount of palladium acetate in molten tetrabutylammonium acetate without the need for any additional ligand. The use of this method enabled the coupling of substituted vinyl arenes in reasonable yields to give exclusively the (E,E)‐1,4‐diarylbutadiene motif within 7–10 h. Acrylates, on the other hand, exhibit higher reactivity, and the use of dibutyl acrylate resulted in the quantitative synthesis of dibutyl 2‐methyleneglutarate in less than 2 h. This selectivity is unprecedented in the literature. The role of the ionic liquid and the different catalytic pathways involved in the two processes were also elucidated.

Binary Mixtures of Choline Acetate and Tetrabutylammonium Acetate with Natural Organic Acids by Vibrational Spectroscopy and Molecular Dynamics Simulations.

We present a study of several mixtures obtained by the mixing of two organic acetate-based salts (choline acetate, ChAc, or tetrabutylammonium acetate, TBAAc) with three different natural organic acids (ascorbic acid, AA, citric acid, CA, and maleic acid, MA). The structures of the starting materials and of the mixtures were characterized by infrared spectroscopy (FT-IR) and classic molecular dynamics simulations (MD). The thermal behavior was characterized by differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). The obtained mixtures, especially the ChAc-based ones, strongly tend to vitrify at low temperatures and are stable up to 100-150 °C. The FTIR measurements suggest the formation of a strong H-bond network: the coordination between acids and ChAc or TBAAc takes place by the donation of the H-bond by the acids to the oxygen of the acetate anion, which acts as an acceptor (HBA). The comparison with MD analysis indicates that acids predominantly exploit their more acidic hydrogens. In particular, we observe the progressive shift of νC═O and νOH when the ratios of acids increase. The structural differences between the two studied cations influence the spatial distribution of the components in the mixture bulk phases. In particular, the analysis of the theoretical structure function I(q) of the TBAAc-based systems shows the presence of important prepeaks at low q, a sign of the formation of apolar domain, due to the nanosegregation of the alkyl chains.

Fluorescence quenching of deprotonated phenylurea through twisting motion induced by an electron-donating substituent group.

The excited-state proton transfer (ESPT) reaction between anthracen-2-yl-3-phenylurea (PUA) derivatives and tetrabutylammonium acetate (TBAAc) in dimethyl sulfoxide (DMSO) solvent was theoretically investigated using time-dependent density functional theory. The electron-donating methoxy group (OMe) and electron-withdrawing trifluoromethyl group (CF3) were bonded to 2PUA to form OMe-2PUA and CF3-2PUA, respectively. Two hydrogen bonds formed in the 1 : 1 hydrogen-bonded complexes between the 2PUA derivative and acetate ion (AcO-), namely N1-H1⋯O1 and N2-H2⋯O2. Strong charge transfer (CT) due to the electron-donating OMe group led to H1 transfer in the S1 state for the OMe-2PUA:AcO- hydrogen-bonded complex. On the contrary, weak CT due to the electron-withdrawing CF3 group led to H2 transfer in the S1 state for CF3-2PUA. After the ESPT reaction, the binding energies of the hydrogen-bonded complexes strongly decreased in both cases, and this promoted the separation of contact-ion pairs (CIPs*) and formed different types of anionic species. CF3-2PUA- could keep its nearly planar structure in the S1 state and emit "abnormal" fluorescence. On the other hand, the anionic OMe-2PUA- underwent a twisting motion to form a twisted structure in the S1 state with very low energy, and this led to a rapid internal conversion (IC) to quench long-wave fluorescence in the emission spectra.

Access to Electron‐Rich Dibenzofurans through NBu4OAc‐Mediated Palladium Catalysis

AbstractDibenzofuran and its derivatives are ubiquitous and important medicinal and natural products. Many contain electron‐rich aryl rings. Forming the key intramolecular Ar−Ar bond using traditional cross‐coupling is difficult. The C−H functionalisation (C−H activation) approach is, in principle, far more useful. However, we previously found that the well‐established conditions, which promote C−H functionalisation through Concerted Metalation‐Deprotonation (CMD), proved unsatisfactory. Herein, we report a Pd‐catalysed C−H functionalisation protocol that works with electron‐rich arenes. We use tetrabutylammonium acetate (NBu4OAc), which we suspect can act as base, ligand and solvent, rendering this protocol a simple and efficient route to electron‐rich dibenzofurans.

Acidic Ionic Liquids in Ultrasonic Irradiation Conditions Promote the Nucleophilic Addition to Chalcone Derivatives

Under solvent-free conditions and with the help of ultrasonic irradiation, the synthesis of pyrano[3,2-c]chromen and pyrano[3,2-c]quinolin derivatives was promoted by four different ionic liquids. All reaction was performed at 100 °C and had good to excellent yields. 1-butyl-1-methylpyrrolidin-1-ium acetate (A), 1-butyl-1-methylpiperidin-1-ium acetate (B), N,N,N-triethylbutan-1-aminium acetate (C), and tetrabutylammonium acetate (D) as perfect ionic liquids for this reaction show remarkable catalytic activity. The work was simply developed for the reaction of chalcones with 4-hydroxy-1-methylquinolin-2(1H)-one/4-hydroxycoumarin to perform pure products of pyran heterocycles.

Improved Process for the Synthesis of 3-(3-Trifluoromethylphenyl)propanal for More Sustainable Production of Cinacalcet HCl.

Cinacalcet (I), sold as hydrochloride salt, is a calcimimetic drug which has been approved for the treatment of secondary hyperparathyroidism in patients with chronic renal disease and for the treatment of hypercalcemia in patients with parathyroid carcinoma. Here, an improved method for the synthesis of 3-(3-trifluoromethylphenyl)propanal (II), a key intermediate for the preparation of I, is described. The protocol required a Mizoroki-Heck cross-coupling reaction between 1-bromo-3-(trifluoromethyl)benzene and acroleine diethyl acetal, catalyzed by Pd(OAc)2 in the presence of nBu4NOAc (tetrabutylammonium acetate), followed by the hydrogenation reaction of the crude mixture of products in a cascade process. Palladium species, at the end of the reaction, were efficiently recovered as Pd/Al2O3. The procedure was developed under conventional heating conditions as well as under microwave-assisted conditions. The obtained mixture of 1-(3,3-diethoxypropyl)-3-(trifluoromethyl)benzene (III), impure for ethyl 3-(3-trifluoromethylphenyl) propanoate (IV), was finally treated, under mild conditions, with potassium diisobutyl-tert-butoxyaluminum hydride (PDBBA) to obtain after hydrolysis 3-(3-trifluoromethylphenyl)propanal (II), in an excellent overall yield and very high purity. Microwave conditions permitted a reduction in reaction times without affecting selectivity and yield. The final API was obtained through reductive amination of (II) with (R)-(+)-1-(1-naphthyl)ethylamine (V) using a catalyst prepared by us with a very low content of precious metal.

Measurements of the Dissociation Heats of Tetrabutylammonium Acetate and Tetrabutylammonium Hydroxide Ionic Semiclathrate Hydrates

Measurements of the Dissociation Heats of Tetrabutylammonium Acetate and Tetrabutylammonium Hydroxide Ionic Semiclathrate Hydrates

Anion-exchange facilitated selective extraction of sulfate and phosphate by overcoming the Hofmeister bias.

Selective recognition and removal of sulfate and phosphates from aqueous media in the presence of highly competing anions is very demanding because of their biological and environmental implications. In this paper, we present the anion recognition approach for the selective and efficient extraction of sulfate by nitrophenyl-functionalized tris-urea receptors (L1-L2) from highly competitive aqueous media with an equivalent concentration of nitrate and other anions. Tetrabutylammonium hydroxide has been used for the first time as a phase transfer anionic extractant for sulfate-exchange from the aqueous phase to the organic phase (dichloromethane) containing a tris-urea receptor (L1-L3). The sulfate extraction efficacy of L2 (≈84-90%) was observed to be higher than those of L1 (≈76-82%) and L3 (≈68-75%) in competitive extraction experiments. In contrast, an analogous nitrophenyl-functionalized tris-thiourea receptor (L4) has been recognized for the selective and efficient extraction of phosphates from aqueous media in the presence of several competing anions including sulfate and nitrate, with ≈85-92% extraction efficiency. In this case, tetrabutylammonium acetate has been used as a phase transfer anionic extractant for phosphate exchange between the two immiscible phases. Due to the higher acidity of tris-thiourea -NH groups in comparison to the analogous tris-urea, tetrabutylammonium hydroxide could deprotonate a hydrogen bond donating -NH group of the thiourea receptor and phosphate extraction was observed to be inefficient in such a case. Several liquid-liquid extraction (LLE) experiments have been carried out to establish the selective removal of sulfate and phosphates by the tripodal receptors from competitive aqueous media having different combinations of two or more anions. The LLE products obtained from organic phases were characterized by NMR (1H, 13C, 31P, and 19F) spectroscopy to affirm the oxoanion selectivity of the receptors and purity of the complexes. The tripodal receptors can easily be recycled for successive extraction cycles by simply washing the LLE products (oxoanion complexes) with a methanol-water (1 : 1, v/v) solvent system followed by filtration.

Direct Synthesis of 3-Aryl Substituted Isocoumarins and Phthalides through Palladium Acetate Catalyzed C(sp2 )-H Activation in Ionic Liquids.

A novel Pd-catalysed oxidative coupling between benzoic acids and vinylarenes or acrylates to furnish isocoumarins and phthalides is reported. The reaction proceeds smoothly in molten tetrabutylammonium acetate via a selective C-H bond activation, with very low percentage of ligand-free palladium acetate as the catalyst, under atmospheric pressure of oxygen. Sub-stoichiometric amount of copper acetate is also required as a reoxidant for the palladium.

Synthesis of Enamines, Aldehydes, and Nitriles from CO2: Scope of the One-Pot Strategy via Formamides.

Tetrabutylammonium acetate (TBAA) and Cu(OAc)2 worked as a binary catalytic system for the solvent-free N-formylation of amines with CO2 and PhSiH3. This catalysis making C-H and C-N bonds with CO2 was coupled with the C-C bond-forming reactions to achieve the one-pot synthesis of enamines, aldehydes, and nitriles. The X-ray crystal structure of a Cu(OAc)2-TBAA complex was also revealed.

Polymerization of N-phenylmaleimide Using Different Catalysts

The polymerization of N-phenylmaleimide (N-PMI) employing sodium phosphate tribasic as a catalyst has been successfully investigated in this study. The effect of dimethyl sulfoxide (DMSO) solvent on the principal catalyst, sodium phosphate tribasic, was extensively studied. The effects of several catalysts, including tetrabutylammonium acetate (TBAA), 4-dimethylaminopyridine (DMAP), Benzyl triethylammonium chloride (BTEAC), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,4-diazabicyclo[2.2.2]octane (DABCO), 1-Methylimidazole (1MA) and potassium phthalimide salt on polymerization of N-PMI have been discussed in this study. Additionally, the kinetics of polymerization in DMSO with Na3PO4 as the initiator is investigated. By using 1H and 13C nuclear magnetic resonance (NMR) spectrum analysis, attenuated total Reflection-Fourier transform infrared (ATR-FTIR), the resultant polymers were identified. Thermogravimetric and differential scanning calorimetric analyses were used to study the thermal behaviors. Our results prove that a salt form of catalyst can initiate the polymerization of N-PMI in dimethyl sulfoxide at a suitable concentration and under favorable conditions.

Electrochemical Oxidation‐Induced Oxyphosphorylation of Alkenes and Alkynes with Water via Hydrogen Atom Transfer

AbstractA metal‐ and exogenous‐oxidant‐free oxidation‐induced oxyphosphorylation of alkenes and alkynes with water for β‐ketophosphonates has been developed through the radical coupling under electrochemical conditions. This protocol is compatible with a wide range of alkenes, alkynes, and diarylphosphorus derivatives, and enables the gram‐scale synthesis of β‐ketophosphonates. The mechanistic study revealed that the P radicals were generated via hydrogen atom transfer (HAT) event jointly mediated by tetrabutylammonium acetate and anode oxidation process.magnified image

Understanding the physical and thermodynamic properties of monoethanolamine‐ionic liquids for solvent screening in CO2 capture process

AbstractThe physical properties such as density, surface tension, and viscosity of monoethanolamine (MEA)‐ionic liquids (ILs) solvent mixtures were studied experimentally in this work. The ILs namely, tetrabutylammonium acetate TBAAc, tetrabutylammonium bromide TBABr, and tetrabutylammonium hydroxide TBAOH were used. All the above parameters were measured at atmospheric pressure and various temperatures from 283 to 313 K with a 10 K interval. From the measured experimental data, thermodynamic properties such as thermal expansion, excess molar volume, viscosity deviation, and excess Gibbs free energy were also calculated. The physical and thermodynamic properties are more important to understand the solvent behavior during solvent screening in solvent‐based CO2 capture process. The 30 wt% solvent mixture composition was prepared as 28, 25, and 20 wt% MEA mixed with 2, 5, and 10 wt% ILs. Furthermore, a single empirical model was developed from the measured experimental data and the results are correlated. A good agreement was obtained between correlated and experimental data.

Enhancement of the solubility of organic dyes in aqueous ionic solvents doped with surfactants

Natural dyes can be poorly water-soluble, and improving their solubility with accurately designed solvents can benefit their application in most domains. Ionic liquids and deep eutectic solvents, systems with complex and diverse intermolecular interactions, are capable of dissolving compounds of different nature and polarity. A remarkable solubility increase of three natural dyes, indigo, alizarin and curcumin, is observed in the ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate and in the eutectic solvent formed by tetrabutylammonium acetate with lactic acid. Further addition of water and surfactants to these ionic media can make them more suitable and cost-effective for industrial use. By means of molecular dynamics, we exposed striking differences in the solvation of dyes in the ionic liquid and the deep eutectic solvent, with important structural changes upon addition of water. The experimental solubility of the dyes, measured at different compositions and compared with water as solvent, point at the favourable impact of small additions of water and surfactants on the dissolution process.

Aqueous Biphasic Systems Comprising Natural Organic Acid-Derived Ionic Liquids

Despite the progress achieved by aqueous biphasic systems (ABSs) comprising ionic liquids (ILs) in extracting valuable proteins, the quest for bio-based and protein-friendly ILs continues. To address this need, this work uses natural organic acids as precursors in the synthesis of four ILs, namely tetrabutylammonium formate ([N4444][HCOO]), tetrabutylammonium acetate ([N4444][CH3COO]), tetrabutylphosphonium formate ([P4444][HCOO]), and tetrabutylphosphonium acetate ([P4444][CH3COO]). It is shown that ABSs can be prepared using all four organic acid-derived ILs paired with the salts potassium phosphate dibasic (K2HPO4) and tripotassium citrate (C6H5K3O7). According to the ABSs phase diagrams, [P4444]-based ILs outperform their ammonium congeners in their ability to undergo liquid–liquid demixing in the presence of salts due to their lower hydrogen-bond acidity. However, deviations to the Hofmeister series were detected in the salts’ effect, which may be related to the high charge density of the studied IL anions. As a proof of concept for their extraction potential, these ABSs were evaluated in extracting human transferrin, allowing extraction efficiencies of 100% and recovery yields ranging between 86 and 100%. To further disclose the molecular-level mechanisms behind the extraction of human transferrin, molecular docking studies were performed. Overall, the salting-out exerted by the salt is the main mechanism responsible for the complete extraction of human transferrin toward the IL-rich phase, whereas the recovery yield and protein-friendly nature of these systems depend on specific “IL-transferrin” interactions.

All-Inorganic Perovskite Solar Cells with Tetrabutylammonium Acetate as the Buffer Layer between the SnO2 Electron Transport Film and CsPbI3.

All-inorganic CsPbI3 perovskites have great potential in tandem cells in combination with other photovoltaic devices. However, CsPbI3 perovskite solar cells (PSCs) still face a huge challenge, resulting in a low power conversion efficiency (PCE) relative to organic-inorganic PSCs. In this work, we introduced tetrabutylammonium acetate (TBAAc) as a buffer layer between the SnO2 electron-transport layer (ETL) and CsPbI3 all-inorganic perovskite film interface for the first time. TBAAc not only improved the conductivity of SnO2 ETL but also formed a 1D TBAPbI3 layer between the SnO2 ETL and the 3D CsPbI3 all-inorganic perovskite film, thereby enhancing the stability and passivating the surface defects of the CsPbI3 perovskite to fabricate high-efficiency carbon-counter electrode (CE)-based CsPbI3 solar cells. We fabricated carbon-CE-based hole-transporting layer ( HTL)-free PSCs with an FTO/SnO2/TBAAc/CsPbI3/C structure. The open-circuit voltage (Voc), short circuit current density (Jsc), PCE, and fill factor of the champion CsPbI3 PSCs simultaneously enhanced to 1.08 V, 17.48 mA/cm2, 12.79, and 67.8%, respectively. This PCE is currently one of the high efficiencies reported for the above planar-structured carbon-CE-based CsPbI3 PSCs to date. Moreover, the optimized device exhibits excellent stability, which retained over 83% of its initial PCE after 350 h. This work provides a facile way of simultaneous optimization of the SnO2 ETL and the CsPbI3 perovskite layer to fabricate stable and high-efficiency carbon-CE-based CsPbI3 PSCs.

Separation of Albumin from Bovine Serum Applying Ionic-Liquid-Based Aqueous Biphasic Systems

In this work, the extraction and separation of bovine serum albumin (BSA) from its original matrix, i.e., bovine serum, was performed using a novel ionic-liquid-based aqueous biphasic system (IL-based ABS). To this end, imidazolium-, phosphonium-, and ammonium-based ILs, combined with the anions’ acetate, arginate and derived from Good Buffers, were synthesized, characterized, and applied in the development of ABS with K2HPO4/KH2PO4 buffer aqueous solutions at pH 7. Initial studies with commercial BSA revealed a preferential migration of the protein to the IL-rich phase, with extraction efficiencies of 100% obtained in a single-step. BSA recovery yields ranging between 64.0% and 84.9% were achieved, with the system comprising the IL tetrabutylammonium acetate leading to the maximum recovery yield. With this IL, BSA was directly extracted and separated from bovine serum using the respective ABS. Different serum dilutions were further investigated to improve the separation performance. Under the best identified conditions, BSA can be extracted from bovine serum with a recovery yield of 85.6% and a purity of 61.2%. Moreover, it is shown that the BSA secondary structure is maintained in the extraction process, i.e., after being extracted to the IL-rich phase. Overall, the new ABS herein proposed may be used as an alternative platform for the purification of BSA from serum samples and can be applied to other added-value proteins.

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.

Dissolution behavior of cellulose in a novel cellulose solvent

We have found that cellulose can be dissolved rapidly in the mixed solvent of tetrabutylammonium acetate (TBAA) and a polar aprotic solvents (PAS) at 50 °C and the obtained cellulose solution could be regenerated into cellulose film and fiber. The factors affecting the dissolution behavior of cellulose were investigated and it was found that the solubility and dissolution rate of cellulose in the mixed solvent are significantly dependent on the species of PAS and the molar ratio of PAS/TBAA. The suitable PAS are dimethyl sulfoxide, pyridine, dimethylacetamide, dimethylformamide and N-Methyl-2-pyrrolidone, and dimethyl sulfoxide is the best one in regard to the solubility and dissolution rate of cellulose. The optimal molar ratio of PAS/TBAA was determined by DN of the polar aprotic solvents. The dissolution behaviour of cellulose in the mixed solvent was proposed to involve the solvent diffusion, solvation of TBA+ as well as disruption of the intermolecular or intramolecular hydrogen bonds of cellulose.