Presence Of Tetraethylammonium Bromide Research Articles

Fabrication of hierarchical Lewis acid Sn-BEA with tunable hydrophobicity for cellulosic sugar isomerization

Abstract Lewis acid Sn-BEA catalysts with tunable morphology and hydrophobicity were successfully synthesized by the recrystallization of post-synthetic Sn-BEA in the presence of ammonium fluoride (NH4F) and tetraethylammonium bromide (TEABr). Three-dimensionally ordered mesoporous imprinted (3DOm-i) and nanocrystalline Sn-BEA catalysts with hydrophobic surface were synthesized for the first time by the method. This recrystallization method includes the dissolution of crystalline zeolite BEA by fluoride ions and the rearrangement of different types of silanol defects in the presence of TEABr. The method allows the final products to simultaneously inherit the morphology of their parent Al-BEA zeolites, and significantly reduce silanol defects within the catalysts. The Sn-BEA catalysts synthesized from the recrystallization method show largely enhanced catalytic performance for both glucose isomerization and bulky lactose isomerization in different solvents, which is presumably due to the hydrophobic surface and improved molecular transport property in the hierarchical zeolites. The recrystallization approach is a facile and reliable strategy to improve the hydrophobicity of zeolite catalysts with tunable morphologies ranging from nanocrystals to hierarchical structures.

Bio‐based Epoxy Resins from Epoxidized Plant Oils and Their Shape Memory Behaviors

AbstractIn this study, bio‐based epoxy materials containing functionalized plant oil, such as epoxidized soybean oil (ESO) and epoxidized linseed oil (ELO), were processed with 4‐methylhexahydrophthalic anhydride (MHPA) as a curing agent. In the presence of tetraethylammonium bromide, the curing reaction of epoxidized plant oil and MHPA proceeded at 130 °C to give transparent plant oil‐based epoxy materials. The resulting bio‐based epoxy materials exhibited relatively soft and flexible characters, due to the aliphatic chains of plant oil. The thermal and mechanical properties of the ESO/MHPA polymers depended on the feed molar ratio of anhydride to oxirane. The mechanical properties such as tensile strength and Young's modulus of the ELO/MHPA polymer increased, compared with those of the ESO/MHPA polymer. The glass transition temperature of the ELO/MHPA polymer was higher than that of the ESO/MHPA polymer, because of the high oxirane number of ELO. Furthermore, the ELO/MHPA polymer showed excellent shape memory property.

Electrodeposition of cobalt from aqueous sulphate solutions in the presence of tetra ethyl ammonium bromide

The effect of tetra ethyl ammonium bromide (TEAB) as an additive on the structural, morphological characteristics of the cobalt metal produced from aqueous sulphate solutions was investigated. The concentration of TEAB was varied in a range of 1–50 mg/L to evaluate its effect on current efficiency, energy consumption and quality of electrodeposited cobalt metal. Smooth and bright deposits of cobalt were obtained at low concentration of TEAB (10 mg/L) maintaining a current efficiency of 99.6%, with a low energy consumption of 2.38 kW·h/kg. X-ray diffraction studies reveal that (100) plane is the most preferred plane of crystal growth during cobalt electrodeposition. Scanning electron micrographs indicate that smooth and uniform deposit of cobalt is obtained at 10 mg/L beyond which the deposit quality deteriorates. Cyclic voltammetric studies indicate that the presence of TEAB in the electrolytic bath polarizes the cathode and decreases the cathodic current considerably. XPS results confirm the electrodeposition of high pure cobalt with no sign of chemical bonding with TEAB as evident from the FTIR spectra.

ChemInform Abstract: 2‐Iodoxybenzoic Acid‐Mediated Transformation of Halogenated Hydrocarbon in the Presence of Tetraethyl Ammonium Bromide.

AbstractThe reagent can be easily recycled and reoxidized.

2-Iodoxybenzoic Acid-Mediated Transformation of Halogenated Hydrocarbon in the Presence of Tetraethyl Ammonium Bromide

2-Iodoxybenzoic acid (IBX) has been shown to react with alkyl halides in the presence of tetraethyl ammonium bromide to give 2-iodobenzoate esters. Most of the monohalides and dihalides reacted easily with moderate to good yields. The 2-iodobenzoate esters containing other functional groups can offer further synthetic uses. The 2-iodobenzoic acid can be recycled easily and oxidised to IBX again.

Room-Temperature Synthesis of BiOBr Sub-Microflowers and Their Photocatalytic Properties

Flower-like BiOBr sub-microstructures about 500 nm in diameter have been synthesized in the presence of tetraethylammonium bromide (TEAB) via a solution route at room temperature. SEM observation shows that these sub-microflowers are composed of nanoflakes with the thickness of 20 nm. The photocatalytic activities of flower-like BiOBr were evaluated by the degradation of methyl orange (MO) and phenol under visible-light and UV-light irradiation, which presented the efficiencies up to 97% within 1.5 h and 45% within 4 h, respectively.

Structure–property relationship in new photo-cured dimethacrylate-based dental resins

ObjectivesIn this study five novel dimethacrylates of different chain lengths having rigid aromatic rings were synthesized and proposed as possible dental monomers for dental resin mixtures. MethodsFour monomers were prepared by the reaction of glycidyl methacrylate with dicarboxylic acid esters obtained from phthalic anhydride and 1,3-propylene, 1,4-butylene, 1,5-penthylene and 1,6-hexylene glycols. The addition reaction of glycidyl methacrylate and the acidic compound was carried out in the presence of tetraethylammonium bromide. The fifth monomer was obtained from 1,5-penthylene glycol-based dimethacrylate by blocking its hydroxyl groups with acetyl groups. The monomers were photo-copolymerized with triethyleneglycol dimethacrylate (TEGDMA) in the presence of a photoinitiator which was 2,2-dimethoxy-2-phenyloacetophenone. Unfilled polymers were evaluated for photopolymerization conversion and volumetric curing shrinkage. Water sorption, water solubility, flexural strength and hardness were measured. The prepared polymers were also subjected to dynamic mechanical studies (DMA). ResultsResults show that, increasing the distance between double bonds decreases flexural modulus and hardness. As expected, the curing shrinkage increased with increasing degree of conversion. The acetylation of hydroxyl groups resulted in improved water uptake properties of the compositions. It was demonstrated that, depending upon the content of acetyl groups in the network, the glass transition temperature may be significantly lowered. In polymers with large amounts of pendant groups, β relaxation overlaps with α relaxation (glass transition temperature), and it is the former that discloses the maximum on the tanδ curve. SignificanceThe systematic change in the length of the new dimethacrylates provided insight into the effects on the resultant material properties. It was shown in the article that the properties of the new monomers compare favorably with properties of the commercially available resins.

Thermal properties, curing characteristics and water absorption of soybean oil-based thermoset

Epoxidized soybean oil (ESO) was successfully thermal-cured by using methylhexahydrophthalic anhydride (MHHPA) curing agent, in the presence of tetraethylammonium bromide (TEAB) catalyst of varied concentration (0.3-0.8 phr). The polyesterification process of ESO thermoset was proven and supported by Fourier transforms infrared spec- troscopy (FTIR) and gas chromatography-mass spectroscopy analysis (GC-MS). A possible chemical reaction of the MHHPA, TEAB and ESO was proposed based on the experimental work. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) revealed that there is a positive relationship between the degree of conversion and crosslink density of ESO thermoset with TEAB concentration. The kinetics of water absorption of the ESO thermoset were found to conform to Fickian law behavior.

Synthesis of 6-Hydroxymethylpterin α- and β-D-Glucosides

The key precursor, N(2)-(N,N-dimethylaminomethylene)-6-hydroxymethyl-3-[2-(4-nitrophenyl)ethyl]pterin (11) was efficiently prepared from 2,5,6-triamino-4-hydroxypyrimidine (8) in 5 steps. The first, unequivocal synthesis of 6-hydroxymethylpterin α-D-glucoside (6a) was achieved by treatment of 11 with 4,6-di-O-acetyl-2,3-di-O-(4-methoxybenzyl)-α-D-glucopyranosyl bromide (16) in the presence of tetraethylammonium bromide and N-ethyldiisopropylamine, followed by removal of the protecting groups, while 6-hydroxymethylpterin β-D-glucoside (6b) was prepared by means of selective glycosylation of 11 with 2,3,4,6-tetra-O-benzoyl-α-D-glucopyranosyl bromide (12) in the presence of silver triflate and tetramethylurea.

IBX/TEAB-mediated oxidative dimerization of thioamides: synthesis of 3,5-disubstituted 1,2,4-thiadiazoles

Thioamides undergo oxidative dimerization on treatment with hypervalent iodine(V)-containing reagents, particularly o-iodoxybenzoic acid (IBX), in the presence of tetraethylammonium bromide (TEAB) to generate 3,5-disubstituted 1,2,4-thiadiazoles in excellent yield.

2-Iodoxybenzoic Acid/Tetraethylammonium Bromide/Water: An Efficient Combination for Oxidative Cleavage of Acetals

A simple and efficient procedure has been developed for the oxidation of cyclic and acyclic acetals to the corresponding hydroxyalkyl carboxylic esters and simple esters, respectively. 2-lo-doxybenzoic acid (IBX) in the presence of tetraethylammonium bromide was employed for the reaction in aqueous media. The salient features of the protocol include short reaction time, environmentally benign reagents and solvent, and moderate to high yields.

Insights into the energetics and mechanism underlying the interaction of tetraethylammonium bromide with proteins

Calorimetry has been employed to investigate the quantitative energetic aspects and mechanism underlying protein–tetraethylammonium bromide (TEAB) interactions. Differential scanning calorimetry and UV–Visible spectroscopy have been used to study the thermal unfolding of three proteins of different structure and function (bovine serum albumin, α-lactalbumin, and bovine pancreatic ribonuclease A). The mode of interaction has been studied by using isothermal titration calorimetry, which demonstrates the absence of appreciable specific binding of TEAB to the protein. This suggests the involvement of solvent mediated effects and, possibly weak non-specific binding. The thermal unfolding transitions were found to be calorimetrically reversible for α-lactalbumin and bovine pancreatic ribonuclease A and partially reversible in the case of bovine serum albumin. The results indicate protein destabilization promoted by the TEAB interaction. The preferential interaction parameters of TEAB with α-lactalbumin and ribonuclease A confirm that an increased interaction of the hydrophobic groups of the TEAB with that of the protein upon denaturation is responsible for the reduced thermal stability of the protein. The decrease in the thermal stability of proteins in the presence of TEAB is well supported by a red shift in the intrinsic fluorescence of these proteins leading to conformational change thereby shifting the native ⇌ denatured equilibrium towards right. The forces responsible for the thermal denaturation of the proteins of different structure and function in the presence of TEAB are discussed.

Simple Bromination of Activated Arenes by IBX Amide Resin and Tetraethylammonium Bromide.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis and Crystal Structure of Bis(tetraethylammonium) Octabromo‐triselenate(II)‐{dibromodiselenate(I)}, [NEt4]2[Se3Br8(Se2Br2)], the Salt of a Mixed‐valence Bromoselenate(II, I) Anion

AbstractThe brown crystals of [NEt4]2[Se3Br8(Se2Br2)] (1) were obtained when selenium and bromine reacted in the solution of acetonitrile in the presence of tetraethylammonium bromide. The crystal structure of 1 has been determined by the X‐ray methods and refined to R = 0.0308 for 10433 reflections. The crystals are monoclinic, space group P21 with Z = 2 and a = 12.0393(3) Å, b = 11.8746(3) Å, c = 13.1946(3) Å, β = 96.561(1)° (123 K). In the solid state structure the anion of 1 is built up of Se3Br8 unit which consists of a triangular arrangement of three planar SeBr4 units sharing a common edge through two μ3‐bridging Br atoms, and one Se2Br2 molecule which is linked to one of μ3‐bridging Br atoms. The three SeII atoms form a triangle which is almost perpendicular to the planes given by three SeBr4 moieties. The contact between the μ3Br and the SeI atom of the Se2Br2 molecule is 3.1711(8) Å and can be interpreted as a bond of the donor‐acceptor type with the μ3Br as donor and the Se2Br2 molecule as acceptor. The terminal SeII‐Br and μ3Br‐SeII bond lengths are in the ranges 2.3537(7)–2.4737(7) Å and 2.7628(7)–3.1701(7) Å, respectively. The bond lengths in coordinated Se2Br2 molecule are: SeI‐SeI = 2.2636(9) Å, SeI‐Br = 2.3387(11) and 2.3936(8) Å.

Simple Bromination of Activated Arenes by IBX Amide Resin and Tetraethylammonium Bromide

A mild and operationally simple method of brominating activated aromatic compounds using a polymer supported IBX reagent (IBX amide resin) and tetraethylammonium bromide (TEAB) was developed. The activated aromatics, when reacted with IBX amide resin in the presence of TEAB, were easily converted into the brominated aromatics in high yields (>80%) at room temperature.

Acidolysis of epichlorohydrin by acetic acid in the presence of tetraethylammonium bromide

The effects of acid and catalyst concentrations and temperature on the rate of oxirane ring opening in the reaction of epichlorohydrin with acetic acid in the presence of tetraethylammonium bromide were studied.

The anomalous reactivity of the bis(dibutylstannylene) acetal of pentaerythritol: a case of triple activation

The only dibutyltin derivative of pentaerythritol which is observed by refluxing with dibutyltin oxide in methanol is a bis(dibutylstannylene) acetal. This is converted to the expected dibenzyl ether with benzyl bromide, in the presence of tetraethylammonium bromide in boiling toluene, but benzoylation at room temperature gives a tribenzoate. A mechanism is suggested to account for this triple activation.

Alkylation of Phosphate Group of Nucleotides via Tributylstannyl Phosphate Derivatives

Abstract Alkylation reaction of phosphates via tributylstannyl salt was applied to dinucleotide derivatives. Some alkyl groups were successfully introduced into the internucleotidic phosphate by use of alkyl bromides in the presence of tetraethylammonium bromide. In case of thymidylyl(3′-5′)thymidine, the phosphate moiety was alkylated selectively.

Synthesis of a gallosilicate analogue of high silica, large Port Mordenitel

A high silica (SiO2/Ga2O3 = 42) crystalline mordenite containing gallium (III) in framework positions has been prepared by hydrothermal crystallization at 413 K in the presence of tetraethylammonium bromide. Evidence for the presence of framework gallium in the mordenite lattice is obtained from chemical analysis, XRD, framework IR, solid state MASNMR, thermoanalytical studies, sorption and catalytic activity studies. Chemical analysis and NMR data indicate the absence of significant amounts of aluminium (SiO2/Al2O3 > 2400). An increase in the interplanar spacing and unit cell volume as well as a shift to lower wavenumbers of framework vibrations occurs on gallium incorporation in the mordenite lattice. Ga-mordenite exhibited significant ion exchange capacity. The gallium analogue of mordenite exhibited significant catalytic activity and shape selectivity in the isomerization reaction ofm-xylene.

Synthesis and characterization of 1- O-α-lactosyl-( R,S)-glycerols and 1- O-α-lactosyl-3- O-β-lactosyl-( R,S)-glycerols

Coupling of 2,3,6,2′,3′,4′,6′-hepta- O-benzyl-α-lactosyl bromide with an equimolar amount of 1- O-acetyl-2- O-benzyl-( R,S)-glycerols in the presence of tetraethylammonium bromide and 4A molecular sieves in 1,2-dichloroethane afforded 3- O-acetyl-2- O-benzyl-1- O-(2,3,6,2′,3′,4′,6′-hepta- O-benzyl-α-lactosyl)-( R,S)-glycerols in 20.4% yield, which were deprotected to give 1- O-α-lactosyl-( R,S)-glycerols. 2- O-Benzyl-3- O-(2,3,6,2′,3′,4′,6′-hepta- O-acetyl-β-lactosyl)-1- O-(2,3,6,2′,3′,4′,6′-hepta- O-benzyl-α-lactosyl) -( R,S)-glycerols were obtained in 61% yield by the reaction of hepta- O-acetyl-α-lactosyl bromide and 2- O-benzyl-1- O-(2,3,6,2′,3′,4′,6′-hepta- O-benzyl-α- lactosyl)-( R,S)-glycerols in the presence of mercury(II) cyanide in benzene-nitromethane; deprotection afforded 1- O-α-lactosyl-3- O-β-lactosyl-( R,S)-glycerols in an overall yield of 24%. The two target materials are useful in the assessment of the binding properties of d-galactosyl-terminated glyceryl glycosides to the asialoglycoprotein receptor of normal rabbit and human hepatocytes.