Aqueous Hydrobromic Acid Research Articles

Hydrobromination of hydroxyl-terminated polybutadiene (HTPB) resin under optimal conditions with aqueous hydrobromic acid using response surface methodology (RSM)

Hydrobromination of hydroxyl-terminated polybutadiene (HTPB) resin under optimal conditions with aqueous hydrobromic acid using response surface methodology (RSM)

Enhancing and Extinguishing the Different Emission Features of 2D (EA1−xFAx)4Pb3Br10 Perovskite Films

Abstract2D hybrid perovskites are attractive for optoelectronic devices. In thin films, the color of optical emission and the texture of crystalline domains are often difficult to control. Here, a method for extinguishing or enhancing different emission features is demonstrated for the family of 2D Ruddlesden–Popper perovskites (EA1−xFAx)4Pb3Br10 (EA = ethylammonium, FA = formamidinium). When grown from aqueous hydrobromic acid, crystals of (EA1−xFAx)4Pb3Br10 retain all the emission features of their parent compound, (EA)4Pb3Br10. Surprisingly, when grown from dimethylformamide (DMF), an emission feature, likely self‐trapped exciton (STE), near 2.7 eV is missing. Extinction of this feature is correlated with DMF being incorporated between the 2D Pb‐Br sheets, forming (EA1−xFAx)4Pb3Br10∙(DMF)y. Without FA, films grown from DMF form (EA)4Pb3Br10, retain little solvent, and have strong emission near 2.7 eV. Slowing the kinetics of film growth strengthens a different emission feature, likely a different type of STE, which is much broader and present in all compositions. Films of (EA1−xFAx)4Pb3Br10∙(DMF)y have large, micron‐sized domains and homogeneous orientation of the semiconducting sheets, resulting in low electronic disorder near the absorption edge. The ability to selectively strengthen or extinguish different emission features in films of (EA1−xFAx)4Pb3Br10∙(DMF)y reveals a pathway to tune the emission color in these compounds.

Solid-liquid-gas reaction accelerated by gas molecule tunnelling-like effect.

Solid-liquid-gas reactions are ubiquitous and are encountered in both nature and industrial processes1-4. A comprehensive description of gas transport in liquid and following reactions at the solid-liquid-gas interface, which is substantial in regard to achieving enhanced triple-phase reactions, remains unavailable. Here, we report a real-time observation of the accelerated etching of gold nanorods with oxygen nanobubbles in aqueous hydrobromic acid using liquid-cell transmission electron microscopy. Our observations reveal that when an oxygen nanobubble is close to a nanorod below the critical distance (~1 nm), the local etching rate is significantly enhanced by over one order of magnitude. Molecular dynamics simulation results show that the strong attractive van der Waals interaction between the gold nanorod and oxygen molecules facilitates the transport of oxygen through the thin liquid layer to the gold surface and thus plays a crucial role in increasing the etching rate. This result sheds light on the rational design of solid-liquid-gas reactions for enhanced activities.

Production of 5-(formyloxymethyl)furfural from biomass-derived sugars using mixed acid catalysts and upgrading into value-added chemicals

In this work, 5-(formyloxymethyl)furfural (FMF) has been produced from biomass-derived hexose sugars within a biphasic reaction mixture consisting of aqueous formic acid (85%), a strong Brønsted acid catalyst, and 1,2-dichloroethane as an organic extractant. Using a combination of aqueous hydrobromic acid and formic acid, under optimized condition (80 °C, 8 h, 10 wt% substrate loading), 68% isolated yield of FMF was obtained from fructose. FMF has been demonstrated as a renewable chemical building block for the synthesis of renewable chemicals of commercial significance such as 5-methylfurfural, 2,5-diformylfuran, and 2,5-furandicarboxylic acid in good to excellent isolated yields.

Aq HBr–NaNO2–KI/air: a new catalytic system for α-monobromination of ketones

An efficient approach for α-bromination of aryl alkyl ketones, utilizing a system consisting of aqueous hydrobromic acid as bromine source, sodium nitrite–KI as catalyst, and air as terminal oxidant, has been developed. The method offers advantages of selective monobromination, mild reaction conditions, broad substrate scope, and good yield. The use of air as the terminal oxidant makes the reaction very attractive from both economical and environmental viewpoints.

Copper nitrate–catalyzed α-bromination of aryl ketones with hydrobromic acid

ABSTRACTAn efficient method for α-bromination of aryl ketones, using the combination of molecular oxygen and aqueous hydrobromic acid as a brominating agent in the presence of the copper nitrate, has been developed. This catalytic system, which uses cheap and readily available reactants, shows good atom economy with water as the only by-product.

Calcium isotope fractionation in liquid chromatography with benzo-18-crown-6 resin in aqueous hydrobromic acid medium

Liquid chromatography operated in a breakthrough mode was employed to study calcium isotope fractionation in the aqueous hydrobromic acid medium. Highly porous silica beads, the inner pores of which were embedded with a benzo-18-crown-6 ether resin, were used as column packing material. Enrichment of heavier isotopes of calcium was observed in the frontal part of respective calcium chromatograms. The values of the isotope fractionation coefficient were on the order of 10−3. The observed isotope fractionation coefficient was dependent on the concentration of hydrobromic acid in the calcium feed solution; a higher HBr concentration resulted in a smaller fractionation coefficient value. The present calcium isotope effects were most probably mass-dependent, indicating that they mostly came from isotope effects based on molecular vibration. Molecular orbital calculations supported the present experimental results in a qualitative fashion. Chromatography operated in aqueous HBr media is a better system of Ca isotope separation than that operated in aqueous HCl media.

Determination of single-ion activity coefficients of hydrogen and bromide ions in aqueous hydrobromic acid solutions based on an ionic liquid salt bridge

Single ion activity coefficients of H+ and Br− in aqueous hydrobromic acid solutions, γH+ and γBr−, have been estimated potentiometrically at 25°C with a hydrogen electrode and a silver–silver bromide electrode, respectively, based on the assumption that the change in the liquid junction potential at the interface between a sample solution and an ionic liquid salt bridge is negligibly small. The mean activity coefficients of HBr calculated from experimentally obtained values of γH+ and γBr− well agree with the literature values over the entire concentration ranges studied, 1.04 × 10−3 to 0.528molkg−1. Overall dependencies of γH+ and γBr− on ionic strength are similar to those found previously in aqueous HCl solutions, but the degree of the dependence is distinctively stronger in both γH+ and γBr−. Plots of γH+ and γBr− as a function of the ionic strength are nearly congruent with the predictions by Fraenkel's smaller-ion shell (SiS) model up to 0.05molkg−1. However, with a further increase in HBr concentration experimental γH+ and γBr− more rapidly increases and decreases, respectively, in comparison with the SiS predictions.

In-situ coordination chemistry within cobalt-containing phthalocyanine nanoporous crystals

Nanoporous crystals formed by the cobalt complex of 2,3,9,10,16,17,23,24-octa(2′,6′-di-iso-propyphenoxy)phthalocyanine were used to demonstrate in situ coordination chemistry by single-crystal-to-single-crystal transformations. Ligand exchange, including the introduction of imidazole with the apparent simultaneous oxidation of the metal centre, was readily achieved by simply adding the new ligand into the solvent in contact with the Phthalocyanine nanoporous crystals (PNCs). In addition, chloride and bromide axial ligands were introduced by the use of aqueous hydrochloric, hydrobromic acid or bromine as reagents.

Re-evaluation of Activity Coefficients in Dilute Aqueous Hydrobromic and Hydriodic Acid Solutions at Temperatures from 0 to 60 °C

Simple two-parameter Huckel equations can be used for the calculation of the activity coefficients in aqueous hydrobromic and hydriodic acid solutions at temperatures from 0 to 60 °C and from 0 to 50 °C, respectively, at least up to a molality of 0.5 mol·kg−1. The data measured by Macaskill and Bates (J. Solution Chem. 12:607–619, 1983) at 25 °C and those measured by Hetzer et al. (J. Phys. Chem. 68:1929–1933, 1964) at various temperatures on galvanic cells without a liquid junction were used in the parameter estimations for the hydrogen bromide (HBr) and hydrogen iodide (HI) solutions, respectively. The latter data consist of sets from 0 to 50 °C at intervals of 5 °C. The parameter values for HBr solutions were also tested using the numerous galvanic cell points from the other three data sets existing in the literature for hydrobromic acid solutions and covering wide range of temperatures from 0 to 60 °C. It was observed in the parameter estimations and tests that all of the estimated parameters are independent of the temperature. The recommended parameter values were additionally tested using the isopiestic data of Macaskill and Bates (see the citation above) and those of Harned and Robinson (Trans. Faraday Soc. 37:302–307, 1941) for dilute HBr and HI solutions at 25 °C, respectively. In more concentrated solutions up to a HBr molality of 4.5 mol·kg−1 and up to a HI molality of 3.0 mol·kg−1, an extended Huckel equation was used, which contains an additional quadratic term with respect to the molality. The parameters for the extended Huckel equations were determined from these isopiestic data and tested using these data and the existing galvanic cell data. The activity and osmotic coefficients calculated from the resulting equations are recommended in the present study for the more concentrated solutions. The recommended values are compared to the activity values reported in several previous tabulations.

Transition Metal Sulfide Hydrogen Evolution Catalysts for Hydrobromic Acid Electrolysis

Mixed metal sulfides containing combinations of W, Fe, Mo, Ni, and Ru were synthesized and screened for activity and stability for the hydrogen evolution reaction (HER) in aqueous hydrobromic acid (HBr). Co- and Ni-substituted RuS(2) were identified as potentially active HER electrocatalysts by high-throughput screening (HTS), and the specific compositions Co(0.4)Ru(0.6)S(2) and Ni(0.6)Ru(0.4)S(2) were identified by optimization. Hydrogen evolution activity of Co(0.4)Ru(0.6)S(2) in HBr is greater than RuS(2) or CoS(2) and comparable to Pt and commercial Rh(x)S(y). Structural and morphological characterizations of the Co-substituted RuS(2) suggest that the nanoparticulate solids are a homogeneous solid solution with a pyrite crystal structure. No phase separation is detected for Co substitutions below 30% by X-ray diffraction. In 0.5 M HBr electrolyte, the Co-Ru electrode material synthesized with 30% Co rapidly lost approximately 34% of the initial loading of Co; thereafter, it was observed to exhibit stable activity for HER with no further loss of Co. Density functional theory calculations indicate that the S(2)(2-) sites are the most important for HER and the presence of Co influences the S(2)(2-) sites such that the hydrogen binding energy at sufficiently high hydrogen coverage is decreased compared to ruthenium sulfide. Although showing high HER activity in a flow cell, the reverse reaction of hydrogen oxidation is slow on the RuS(2) catalysts tested when compared to platinum and rhodium sulfide, leaving rhodium sulfide as the only suitable tested material for a regenerative HBr cell due its stability compared to platinum.

Synthesis of Polycyclic Aromatic Hydrocarbons by Oxybromination

A simple and efficient method has been developed for the oxybromination of six kinds of polycyclic aromatic hydrocarbons with the use of aqueous hydrobromic acid and hydrogen peroxide.The method requires no catalysts,and achieves bromination via the in situ generated active bromine.By controling the reaction temperature and the amount of bromination agent,the reaction can obtain the monobromination or dibromination of polycyclic aromatic hydrocarbons with a yield of 51.1%~94.2%.The oxybromination method is simple,safe,environmental friendly,and suitable for industrial production.The obtained products have been characterized by melting point measurement and 1H NMR.

ChemInform Abstract: Structural Studies Coupling X‐Ray Diffraction and High‐Energy X‐Ray Scattering in the UO22+—HBraq System.

AbstractThe structural chemistry of uranium(VI) in conc.

Structural Studies Coupling X-ray Diffraction and High-Energy X-ray Scattering in the UO22+–HBraq System

The structural chemistry of uranium(VI) in concentrated aqueous hydrobromic acid solutions was investigated using both single crystal X-ray diffraction and synchrotron-based high-energy X-ray scattering (HEXS) to reveal the structure of the uranium(VI) complexes in solution prior to crystallization. The crystal structures of a series of uranyl tetrabromide salts are reported, including Cs(2)UO(2)Br(4), Rb(2)UO(2)Br(4)·2H(2)O, K(2)UO(2)Br(4)·2H(2)O, and (NH(4))(2)UO(2)Br(4)·2H(2)O, as well as a molecular dimer of uranium(VI), (UO(2))(2)(OH)(2)Br(2)(H(2)O)(4). Limited correspondence exists between the structures observed in the solid state and those in solution. Quantitative analysis of the HEXS data show an average U-Br coordination number of 1.9(2) in solution, in contrast to the U-Br coordination number of 4 in the solid salts.

Aerobic Oxybromination of Phenols Catalyzed by Sodium Nitrite under Mild Conditions

An efficient catalytic system for oxybromination of phenols under mild conditions has been developed, which utilizes sodium nitrite as the catalyst, dioxygen or air as the terminal oxidant, aqueous hydrobromic acid or molecular bromine as the bromine resource. From both the atom-economic and environmental points of view, the developed protocol is expected to provide a valuable synthetic method for practical applications in laboratory or industry.

자기조립단분자막을 위한 보편적이고 기능화된 긴 사슬 알킬티올 연결자의 제조

본 연구에서는 자기조립단분자막(SAM)의 연구에 유용한 일련의 <TEX>$\omega$</TEX>-mercapto alkyl amine 1 및 <TEX>$\omega$</TEX>-mercapto alkanoic acid 2를 만드는 제조공정을 서술하였다. 먼저 첫 번째 목표물질인 <TEX>$\omega$</TEX>-mercapto alkyl amine 1의 제조방법은 다음과 같다: 먼저 시중에서 시판되는 potassium phthalimide와 <TEX>$\omega$</TEX>-bromo alcohol을 <TEX>$80{^{\circ}C}$</TEX>, DMF 용매에서 치환반응으로 화합물 3을 합성하였다. 아민기와 알코올기를 포함하는 화합물 4을 합성하기 위하여 먼저 화합물 3를 hydrazine hydrate로 환류시킨 후, 이어서 c-HCl로 처리하여 부반응물 5를 수반하여 생성물 4를 76-98% 수율로 만들었다. <TEX>$\omega$</TEX>-aminoakanol 4의 hydroxyl기를 HBr로 브로민화반응을 하여 <TEX>$\omega$</TEX>-bromoamine 화합물 6을 34-97% 수율로 만들었다. 티올기를 도입하기 위하여 화합물 6을 95% 에탄올 속에서 thiourea와 치환 반응하여 <TEX>$\omega$</TEX>-aminoalkanthiuronium 7을 만든 다음, 이 화합물을 센 염기(KOH)와 센 산으로 처리하여 목표화합물, <TEX>$\omega$</TEX>-mercapto alkylamines 1을 총 5단계를 걸쳐서 제조하였다. 덧붙여 두 번째 목표물질인 <TEX>$\omega$</TEX>-mercapto alkanoic acid 2는 다음과 같이 2단계를 통하여 제조하였다: <TEX>$\omega$</TEX>-bromo alkanoic acid를 95% 에탄올 속에서 thiourea로 처리하여 화합물 7을 만든 다음, 센 염기(KOH)를 처리하여 thiuronium bromide 를 제거한 후, 다시 센 산(HCl) 수용액으로 처리하여 두 번째 목표화합물 <TEX>$\omega$</TEX>-mercapto alkanoic acid 2을 얻었다. 제조한 긴 사슬 알킬티올 1과 2 유도체들은 금속(Au, Pt, Ti)에 자기조립단분자 막을 형성함으로써 단백질, 효소 및 다양한 생체분자를 고정하는 연결자로 사용될 수 있으며, 그 밖에 금속의 표면개질을 이용하여 다양한 응용 연구를 위한 화학 도구로 사용될 수 있다. In this research, the preparation processes for making a series of <TEX>$\omega$</TEX>-mercapto alkylamine 1 and <TEX>$\omega$</TEX>-mercapto alkanoic acid 2 useful for studying of the self-assembled monolayer(SAM) are described. The preparation methods of the first goal materials, <TEX>$\omega$</TEX>-mercapto alkylamines 1 were carried out as follows: First, <TEX>$\omega$</TEX>-phthalimide alkanol 3 was synthesized from commercially available potassium phthalimide derivatives and <TEX>$\omega$</TEX>-bromoalkanol in DMF at <TEX>$80{^{\circ}C}$</TEX> via substitution reaction. After refluxing <TEX>$\omega$</TEX>-phthalimide alkanol 3 with hydrazine hydrate in ethanol followed by treating with c-HCl, <TEX>$\omega$</TEX>-aminoalkanol 4 was obtained in 76-98% yield, accompanied with side-product 5. Bromination of hydroxyl moiety of <TEX>$\omega$</TEX>-aminoalkanol 4 using aqueous hydrobromic acid furnished <TEX>$\omega$</TEX>-bromoamine 6 in 34-97% yields. Substitution reaction 6 with thiourea in 95% ethanol gave <TEX>$\omega$</TEX>-aminoalkanthiuronium 7, which was treated with aqueous strong base and aqueous strong sulfuric acid gave desired products, <TEX>$\omega$</TEX>-mercapto alkylamines 1 through overall 5 steps. The second target material, <TEX>$\omega$</TEX>-mercapto alkanoic acid 2 was prepared via 2 steps. <TEX>$\omega$</TEX>-bromo alkanoic acid was reacted with thiourea to give <TEX>$\omega$</TEX>-thiourea alkanoic acid 7 in 69-85%, which was treated with aqueous strong base and strong acid to furnish <TEX>$\omega$</TEX>-mercapto alkanoic acid 2 in 50-98%. The fabricated long-chain alkylthiol(LCAT) can be used as linkers to immobilize protein, enzyme and various kinds of biomolecules on the surface of metallic materials(Au, Pt, Ti) by SAM, and can be useful chemical tools for the application study on the surface modification of metallic materials.

Selective aerobic oxidative dibromination of alkenes with aqueous HBr and sodium nitrite as a catalyst

Various alkenes (internal, terminal, aryl and alkyl substituted) and 1,2-diphenylethyne were efficiently and selectively dibrominated using 2 equivalents of 48% aqueous hydrobromic acid, with air as an oxidant and sodium nitrite as a catalyst. Despite the presence of water, only trans dibromination occurred producing anti-1,2-dibromoalkanes and (E)-1,2-dibromo-1,2-diphenylethene. A comparison of resource demand, waste production and environmental, health and safety issues of the NaNO2 catalyzed aerobic bromination with molecular bromine and other oxidative bromination methods revealed that the proposed method is not only selective and effective but has a better environmental profile.

Sodium Nitrite‐Catalyzed Oxybromination of Aromatic Compounds and Aryl Ketones with a Combination of Hydrobromic Acid and Molecular Oxygen under Mild Conditions

AbstractA novel and efficient catalytic system for the oxybromination of aromatic compounds and aryl ketones utilizing a combination of aqueous hydrobromic acid and molecular oxygen in the presence of sodium nitrite under mild conditions has been developed. The newly developed catalytic system utilizes cheap and readily available reactants, exhibits high bromine atom economy and releases only innocuous water as the by‐product.

Thioacetalization of the carbonyl function, transthioacetalization of acetals, ketals, oximes and hydrazones catalysed by aqueous hydrobromic acid

Thioacetalization of a variety of aldehydes and ketones was achieved in excellent yields at room temperature using thiols or dithiols in aqueous hydrobromic acid. Thioacetals were also prepared by transthioacetalization of oximes, hydrazones, acetals and ketals under similar conditions. The use of aqueous hydrochloric acid, hydrofluoric acid and hydriodic acid for this transformation was also explored.

Synthesis and Application of γ‐Picolinium Bromochromate as a New, Mild and Regioselective Reagent for Bromination of Active Aromatic Compounds.

AbstractFor Abstract see ChemInform Abstract in Full Text.