Boron Trifluoride Research Articles

SYNTHESIS AND CHARACTERIZATION OF POLYEPICHLOROHYDRIN DIOLS

Polyepichlorohydrin (PECH) is a functional polymer with high value in energy materials. Cationic ring-opening polymerization of epichlorohydrin (ECH) with a diol initiator and Lewis or protic acids catalyst, proceeds through an activated monomer mechanism (AM) allowing control of the polymer's average molecular weight and polydispersity index. In the present investigation, PECH diol was synthesized under the catalysis of boron trifluoride etherate, with the ECH monomer:ethylene glycol as an initiator molar ratio of 1:0.045, achieving a low molecular weight nM = 1935 g/mol, low polydispersity index PDI = 1.25, predominantly in the linear chain configuration with the terminal hydroxyl group.

Effect of the Chemical Composition and Geometry of Nanotubes on the Structure and Internal Rotation Barrier of Encapsulated Ammonia‐Boron Trifluoride: A Theoretical Investigation

AbstractThe study of the structure and conformational properties of ammonia–boron trifluoride in the cavity of 24 carbon and inorganic nanotubes using the PBE/3ζ DFT approximation showed that the conformational preference of the encapsulated molecule is determined by geometry and chemical composition of the host nanostructure. The combined effect of these factors leads to the predominance of eclipsed conformation of guest molecule for four endoclusters. In other cases, the main minimum on the potential energy surface corresponds to the staggered or pseudo‐staggered forms of BF3←NH3. The guest molecule carries the electric charge and has a shortened B←N bond. These conclusions are confirmed by the results of the virtual reaction of ammonia and boron trifluoride in the cavity of individual nanotubes.

BF3 ⋅ OEt2 as a Versatile Reagent: Applications in Organic Synthesis

AbstractBoron trifluoride diethyl etherate, commonly referred to as BF3 ⋅ OEt2, plays a crucial role as a potent reagent in various organic transformations, particularly in the synthesis of heterocyclic systems through the establishment of carbon‐carbon & carbon‐heteroatom bonds. Its Lewis acid properties, reactivity, and stability at room temperature make it essential for a wide range of chemical reactions. BF3 ⋅ OEt2 demonstrates remarkable efficacy in processes such as hydroxylation of double bonds, epoxide cleavage, acid esterification, cyanation, coupling, and diverse cyclization reactions, surpassing other Lewis acids in performance. Its significant impact on organic synthesis extends to the formation of natural products, highlighting its profound significance in the realm of chemistry. The unique properties and versatility of boron trifluoride diethyl etherate make it a fundamental tool for a diverse array of chemical transformations. The numerous applications of this reagent in organic synthesis have prompted the development of a comprehensive review, focusing on its various roles and contributions in this field.

Cost‐effective synthesis of unsymmetric tetrazines

Abstract1,2,4,5‐Tetrazines serve as versatile two‐carbon synthons, essential for synthesizing a variety of (hetero)aromatic compounds. Their specific reactivity with certain dienophiles, without interfering with biochemical processes, makes them ideal for bioorthogonal ligation. Despite their broad utility, current synthetic methods are costly and raise safety concerns, particularly during scale‐up. This study introduces safer and more cost‐effective synthetic strategies utilizing zinc chloride or boron trifluoride diethyl etherate as catalysts. These alternatives significantly reduce costs and enhance safety, potentially expanding the applicability of tetrazine synthesis across broader research domains.

Controlled Release of Diborane from Alkali Metal Borohydride using Ionic Liquid-Based Lewis Acids.

Alkali metal borohydrides present a rich source of energy dense materials of boron and hydrogen, however their potential in propellants has been hitherto untapped. Potassium borohydride is a promising fuel with high gravimetric energy density and relatively low sensitivity to air and moisture. Problems arise due to the dehydrogenation of the borohydride on heating with minimal energy release. Common methods to extract both boron and hydrogen by means of borane species involve direct reaction of boron trifluoride species with alkali borohydrides. However, these methods face storage and safety issues due to rapid release of diborane on mixing the reactants. We propose a method of diborane release through controlled release of boron trifluoride by means of a tetrafluoroborate based ionic liquid. The trifluoride is released from the ionic liquid at elevated temperatures and enables safe mixture of the reactants at room temperature. It was found that the reaction between borohydride and boron trifluoride proceeds well above room temperature with potassium borohydride releasing diborane and potassium fluoride. The reaction pathway shows a primary reaction releasing diborane and potassium fluoride and a second less energy efficient step leading to the formation of potassium tetrafluoroborate. A 3D printed propellant formulation was also tested.

Controlled Release of Diborane from Alkali Metal Borohydride using Ionic Liquid‐Based Lewis Acids

AbstractAlkali metal borohydrides present a rich source of energy dense materials of boron and hydrogen, however their potential in propellants has been hitherto untapped. Potassium borohydride is a promising fuel with high gravimetric energy density and relatively low sensitivity to air and moisture. Problems arise due to the dehydrogenation of the borohydride on heating with minimal energy release. Common methods to extract both boron and hydrogen by means of borane species involve direct reaction of boron trifluoride species with alkali borohydrides. However, these methods face storage and safety issues due to rapid release of diborane on mixing the reactants. We propose a method of diborane release through controlled release of boron trifluoride by means of a tetrafluoroborate based ionic liquid. The trifluoride is released from the ionic liquid at elevated temperatures and enables safe mixture of the reactants at room temperature. It was found that the reaction between borohydride and boron trifluoride proceeds well above room temperature with potassium borohydride releasing diborane and potassium fluoride. The reaction pathway shows a primary reaction releasing diborane and potassium fluoride and a second less energy efficient step leading to the formation of potassium tetrafluoroborate. A 3D printed propellant formulation was also tested.

Mechanism of coal pitch pre-hydrogenation catalyzed by metal-free catalytic system and preparation of mesophase pitch

Coal pitch (CP) molecules have high aromaticity, planarity and condensation degree, usually requiring hydrogenation to prepare high-quality mesophase pitch (MP). However, current hydrogenation methods often face challenges such as harsh conditions, residual ash or insufficient hydrogenation. Here, with 5 wt% tetrahydronaphthalene (THN) as the hydrogen donor, hydrogenated CP (HCP) with low ash content and high H/C was prepared at low temperature and pressure via a metal-free catalytic system with boron trifluoride ether (BF3·Et2O) as catalyst and p-toluenesulfonic acid (TsOH) as co-catalyst and 5 wt%. Subsequently, MP was prepared from the HCP, and the mechanisms of catalytic hydrogenation and the formation of mesophase macromolecules were elucidated. The characterization results indicated that CP achieved optimal hydrogenation when the molar ratio of BF3 to TsOH was 1:1. The HCP obtained under this condition can further prepare a wide-area streamlined MP. During the hydrogenation process, TsOH provided proton hydrogen to BF3, forming a complex acid that facilitated carbocation reactions between THN and CP molecules, thereby enhancing hydrogenation efficiency. However, when the molar amount of TsOH exceeded that of BF3, it would catalyze the polymerization of HCP molecules to a certain extent, reducing the hydrogenation effect. Meanwhile, it could introduce more sulfonic acid groups into the molecular structure, causing cross-linking of polycyclic aromatic hydrocarbons and excessive system viscosity during the preparation of the MP, resulting in a mosaic optical texture. This work is of significant importance for promoting the efficient hydrogenation of CP and the preparation of high-quality MP.

Enhancing biphenylene sensitivity for BF3 detection via nitrogen doping: A DFT study

The detection and monitoring of toxic gases are critical components of environmental protection. Boron trifluoride (BF3), in particular, poses a significant threat to both the environment and human health due to its destructive properties. To address this challenge, the development of highly reactive and sensitive sensors for detecting and trapping BF3 is essential. This study explores the potential of pristine biphenylene (BP), boron-doped BP (B-BP), and nitrogen-doped BP (N-BP) as gas sensors for BF3 detection using density functional theory (DFT) calculations at the M062X/6–31 g(d,p) level of theory. We found that nitrogen doping significantly enhances the reactivity of BP toward BF3 originating from strong chemisorption with an adsorption energy of −9.38 kcal/mol. This is accompanied by a notable 19.96 % change in the electronic energy gap, making N-BP an exceptionally sensitive material for gas detection. The results will be supported by natural bond orbital analysis, providing a detailed electronic analysis of the sensing capabilities of N-BP. Our results suggest that n-type doping can be an effective strategy to enhance both the reactivity and sensitivity of carbon-based monolayers for detecting boron trifluoride.

Is There an Adduct of Pyridine N-Oxide and Boron Trifluoride in the Gaseous State? Gas Electron Diffraction vs Mass Spectrometry.

A study of saturated vapor over the pyridine N-oxide-boron trifluoride (PyO-BF3) adduct was carried out at T = 448(5) K by a synchronous gas electron diffraction/mass spectrometry (GED/MS) experiment. Due to the absence of ions in the mass spectrum, indicating the presence of a structure with an O-B dative bond, several models of vapor composition were tested by the GED method. It was found that the dominant molecular form (up to 100%) in vapor is the PyO-BF3 adduct. Using the DFT/M06-2X/aug-cc-pVTZ method, geometric optimization of the molecular ion [PyO-BF3]+ was carried out, which showed its intrinsic instability and dissociation into a [PyO]+ cation and a BF3 molecule. This study certainly demonstrates the significant advantage of the GED method to determine the qualitative and quantitative gas-phase composition of dative-bonded adducts and other noncovalent complexes as well, whereas the interpretation of mass spectra may be ambiguous due to the possible intrinsic instability of ions containing a dative bond. The nature of the O-B bond is discussed in terms of the natural bond orbitals (NBOs) and the quantum theory of atoms in molecules (QTAIM). A comparison of structural and energetic parameters for PyO-BF3 and the previously studied BF3 adducts allows the theoretical comprehension of the nature of the O-B bond to be extended and to explain the different thermal stabilities of these compounds.

Preparation of Semiconducting Films By Electrooxidation of Naphthalene

Due to promising electronic and optical properties, conductive polymers are attracting significant interest. Conductive polymers find applications in electronic devices, e.g. substituted polynaphthalenes are used as blue light sources in OLEDs1. The ability to block the substitution sites where the subsequent polymer unit may be added by functional groups allows the polymer structure to be designed2. Moreover, one of the benefits of conductive polymers is the ability to modify the band gap of these materials by adding substituents to the main chain.Naphthalene, as the smallest polycyclic hydrocarbon, is an interesting precursor for synthesis semiconducting materials. The anodic oxidation of naphthalene has been described several times in the literature3,4, however, only formation of 1,4-polynaphthalene in the form of a granular product has been reported.In our research, we performed naphthalene electrooxidation and investigated the impact of the experimental conditions such as naphthalene concentration, water content, and electrode material on the obtained semiconducting materials. We used mass spectrometry to observe mass progression and determine molecular mass of the obtained polymers. The results of electron microscopy imaging showed fine quality coating. We studied the electronic properties of the polymers by cyclic voltammetry and impedance spectroscopy. Based on the results, we discussed the possible mechanism of the reaction. Samanta, S. K. et al. Synthesis of high molecular weight 1,4-polynaphthalene for solution-processed true color blue light emitting diode. Macromolecules 51, 8324–8329 (2018).Debad, J. F. & Bard, A. J. Electropolymerization of acenaphtho[1,2-k]fluoranthene derivatives: Formation of a new conductive electroactive electrochromic hydrocarbon ladder polymer. J Am Chem Soc 120, 2476–2477 (1998).Zecchin, S., Tomat, R., Schiavon, G. & Zotti, G. Polynaphthylene films from anodic coupling of naphthalene. Synthetic Metals vol. 25 (1988).Huang, Z., Qu, L., Shi, G., Chen, F. & Hong, X. Electrochemical polymerization of naphthalene in the electrolyte of boron trifluoride diethyl etherate containing trifluoroacetic acid and polyethylene glycol oligomer. Journal of Electroanalytical Chemistry 556, 159–165 (2003).

From Building Blocks to Catalysts: The Underinvestigated Potential of Boronic Acid Esters.

Lewis acids are crucial in chemistry, with applications in pharmaceuticals, agrochemicals, and materials science. In main-group chemistry, they offer alternatives to transition metals, prompting our study of halogenated boronic acid esters (BAEs). Although BAEs are well-known, their catalytic potential has been overlooked. Our investigation found their Lewis acidity superior to that of boron trifluoride and comparable to that of tris(pentafluorophenyl)borane. Additionally, their catalysis of the Sakurai allylation of aldehydes has been documented, paving the way for future advancements.

Hydrosilylation of Arynes with Silanes and Silicon-Based Polymer.

Benzyne derived from hexadehydrogenated Diels Alder (HDDA) reactions was found to be an efficient hydrosilylation acceptors. Various silanes can react smoothly with HDDA-derived benzyne to give the arylation products. Lewis acid such as boron trifluoride etherate can accelerate these hydrosilylation reactions. Polyhydromethylsiloxane (PHMS), a widely used organosilicon polymer, was also successfully modified using our method. About 5 % of Si-H bonds in the polymer were inserted by benzynes, giving a functional PHMS with much more solubility in methanol and with a blue-emitting fluorescence behavior. Mechanism research shows that the insertion of benzyne into the Si-H bond probably undergoes a synergistic pathway, which is quite different from the traditional radical-initiated hydrosilylation or transition-metal-catalyzed hydrosilylation.

Unusual Cascade Reactions of 8-Acetoxy-6-hydroxymethyllimonene with Salicylic Aldehydes: Diverse Oxygen Heterocycles from Common Precursors.

Chiral oxygen-containing heterocyclic compounds are of great interest for the development of pharmaceuticals. Monoterpenes and their derivatives are naturally abundant precursors of novel synthetic chiral oxygen-containing heterocyclic compounds. In this study, acid catalyzed reactions of salicylic aldehydes with (-)-8-acetoxy-6-hydroxymethyllimonene, readily accessible from α-pinene, leads to the formation of chiral polycyclic products of various structural types. Three of the six isolated chiral heterocyclic products obtained from salicylic aldehyde contain previously unknown polycyclic ring types. Having carried out the reaction in the presence of Brønsted or Lewis acids (Amberlyst 15, trifluoromethanesulfonic acid, trifluoroacetic acid and boron trifluoride etherate) or aluminosilicates (montmorillonite K10, halloysite nanotubes), we found that the nature of products depends on the catalyst as well as the reaction conditions (reaction time, reactant ratio, presence or absence of solvent). Detailed mechanistic insight on the complex cascade reactions for product formation is provided with extensive experimental and quantum mechanical computational studies.

Novel synthesis of B-doped Ti3C2Tx thin sheets via BF3 Lewis acid etching: Structural insights and Supercapacitor applications

The rising demand for energy storage spurs research on supercapacitor materials, valued for high-power density and long-term cycling, vital in industries. Among two-dimensional materials, MXene, with a general formula of Mn+1XnTx, where M represents early transition metals, X indicates C and/or N, Tx represents functionalized surface groups, and n = 1, 2, or 3, stands out as an ideal candidate for energy storage applications. Here, for the first time, we report the use of a Lewis acid, boron trifluoride (BF3), as an electron-deficient etchant in a sulfuric acid (H2SO4) solution for etching aluminum from the model system Ti3AlC2 MAX (M: transition metals, A: Al, X: carbon.), resulting in the formation of B-doped Ti3C2Tx MXene. Ex-Situ electrochemical X-ray diffraction (XRD) analysis showed reversible (002) plane changes in B-doped Ti3C2Tx MXene, from 5.72° to 7.0°, indicating ions intercalation and deintercalation, a first-time demonstration of significant ion transportation. Such fundamental insight determines that the specific capacitance of B-doped Ti3C2Tx MXene has found to be 396 F/g at current density of 1 A/g. This research introduces a novel synthesis approach aimed at understanding microstructural transformations of B-doped Ti3C2Tx MXene during electrochemical processes. This contributes to the advancement of MXene-based materials for future electrochemical applications.

Phosphoric Acid-Catalyzed Alkene Difunctionalization of 2-Vinylpyridines via HOMO/LUMO Biactivated Diels-Alder Reaction.

The difunctionalization of vinylpyridines based on the cyclization strategy remains rare and underdeveloped, in contrast to the well-developed hydrogen functionalization. Current exploration on [4 + 2] cyclization of vinylpyridines mainly relies on extremely high temperatures and the LUMO activation of vinylpyridines using boron trifluoride as a strong Lewis acid. Herein, we established a phosphoric acid-catalyzed [4 + 2] cyclization reaction of 3-vinyl-1H-indoles and 2-vinylpyridines by means of the LUMO/HOMO bifunctional activation model. This protocol features mild reaction conditions, high functional group tolerance, broad substrate compatibility, and high diastereoselectivity, enabling the efficient construction of various functionalized pyridine-substituted tetrahydrocarbazoles with prominent potential in drug discovery.

Complexes of Zinc-Coordinated Heteroaromatic N-Oxides with Pyrene: Lewis Acid Effects on the Multicenter Donor-Acceptor Bonding.

4-Nitroquinoline-N-oxide (NQO) and 4-nitropyridine-N-oxide (NPO) are important precursors for the synthesis of substituted heterocycles while NQO is a popular model mutagen and carcinogen broadly used in cancer research; intermolecular interactions are critical for their reactions or functioning in vivo. Herein, the effects of the coordination of N-oxide's oxygen atom to Lewis acids on multicenter donor-acceptor bonding were explored via a combination of experimental and computational studies of the complexes of NQO and NPO with a typical π-electron donor, pyrene. Coordination with ZnCl2 increased the positive electrostatic potentials on the surfaces of these π-acceptors and lowered the energy of their LUMO. Analogous effects were observed upon the protonation of the N-oxides' oxygen or bonding with boron trifluoride. The interaction of ZnCl2, NPO, or NQO and pyrene resulted in the formation of dark co-crystals comprising π-stacked Zn-coordinated N-oxides and pyrene similar to that found with protonated or (reported earlier) BF3-bonded N-oxides. Computational studies indicated that the coordination of N-oxides to zinc(II), BF3, or protonation led to the strengthening of the multicenter bonding of the nitro-heterocycle with pyrene, and this effect was related both to the increased electrostatic attraction and molecular-orbital interactions in their complexes.

A general representation of thermodynamic properties for gaseous boron trifluoride

We present an accurate model for predicting the thermodynamic properties for boron trifluoride. Unlike conventional computational approaches that rely on numerous experimental spectroscopy or calorimetry data, this model only uses a small number of molecular constants. The values for entropy, enthalpy, specific heat and Gibbs free energy are computed within the temperature range from 100 to 6000 K and compared with the available experimental data. This representation introduces a new approach to deal with the anharmonic vibrations of polyatomic molecules in general.

Synthesis, biological evaluation, network pharmacology, and molecular docking of benzophenone as antitumor agents

Using Eaton's reagent or boron trifluoride ether, 24 compounds were synthesized in a 1- or 2-step reaction, with the conversion of the methoxy group to the hydroxyl group. Next, the in vitro antitumor activity of all compounds and the antioxidant activity of compounds 1 to 3 were investigated. Compounds 7, 13, 15, 17, 18, 20, 22, and 24 exhibited strong antitumor activity and were considered promising compounds. Among them, compounds 7, 13, and 18 exhibited very strong inhibitory activity against HL-60 cells with IC50 values of 0.55, 0.29, and 0.72 μM, respectively. Furthermore, compounds 1 to 3 exhibited moderate antioxidant activity and their mechanism of action was further validated by computational chemistry. Finally, the antitumor mechanism of the above 8 compounds was investigated through network pharmacology and molecular docking, and 19 key genes and 20 pathways were obtained. These results will allow future development of benzophenone and its derivatives.

Preparation of Mesophase Pitch with Fine-Flow Texture from Ethylene Tar/Naphthalene by Catalytic Synthesis for High-Thermal-Conductivity Carbon Fibers.

Mesophase pitch is usually prepared by radical polymerization or catalytic polymerization from coal tar, petroleum, and aromatic compounds, and the catalytic synthesis of mesophase pitch from pure aromatic compounds is more controllable in the preparation of high-quality mesophase pitch. However, the corrosive and highly toxic nature of the catalyst has limited the further development of this method. In this study, mesophase pitch was synthetized using ethylene tar and naphthalene as raw materials and boron trifluoride diethyl etherate as a catalyst. The effect of the catalytic reaction on the structure and properties of the mesophase pitch was investigated. The results show that naphthalene plays an important role in the mesophase content and reaction pressure (from above 6 MPa to 2.35 MPa). Mesophase pitch with fine-flow texture can be prepared by introducing more methylene groups, naphthenic structures, and aliphatic hydrocarbons during synthesis. Carbon fibers prepared from mesophase pitch show a split structure, and the thermal conductivity is 730 W/(m·K). This work provides theoretical support for lower toxicity and causticity and for reaction-controlled technology for the synthesis of high-purity mesophase pitch.

RIFM fragrance ingredient safety assessment, 2-propanol, reaction products with boron trifluoride and 5-ethylidenebicyclo[2.2.1]hept-2-ene, CAS registry number 90530-04-4

RIFM fragrance ingredient safety assessment, 2-propanol, reaction products with boron trifluoride and 5-ethylidenebicyclo[2.2.1]hept-2-ene, CAS registry number 90530-04-4