Excess Bromine Research Articles

Visible Light‐Promoted Mono‐Bromination of Aniline Derivatives and Nitrogen‐Containing Heterocyclic Compounds via Electron Donor‐Acceptor Complex

AbstractWe present a successful development of a photo‐induced mono‐bromination method for anilines, which eliminates the requirement for photocatalysts and excess bromine sources. Experimental investigations, complemented by computational analyses, establish that this method operates via the formation of an electron donor‐acceptor (EDA) complex. This innovative approach enables the synthesis of highly regioselective mono‐brominated products across a diverse range of substrates, all achieved under mild reaction conditions.

Influence of strong bromine binding complexing agent in electrolytes on the performance of hydrogen/bromine redox flow batteries

1-n-Hexylpyridin-1-ium bromide [C6Py]Br is investigated in this work as bromine complexing agent (BCA) in aqueous bromine electrolytes on its influence on hydrogen bromine redox flow battery (H2/Br2-RFB) performance. [C6Py]+-cations bind bromine of aqueous polybromide solutions safely in an additional fused salt phase limiting the vapor pressure of Br2. Dissolved in aqueous electrolyte solutions, however, [BCA]+ cations drastically lower PFSA membranes' conductivity in the H2/Br2-RFB. In this work the combination of the very strong bromine-binding [C6Py]+cation and an excess of bromine in the electrolyte lead to an almost complete absorption of 99.6 mol% [C6Py]+ into the fused salt within the electrolyte's operation range. In comparison to similar application of short side chain 1-ethylpyridinium bromide, adverse effects are stronger compensated by use of [C6Py]Br. Increases in membrane resistance of the membrane in contact with [C6Py]+ cations are reversible in contrast for contact with [C2Py]+ cations. Electrolytes are cycled for at least 12 cycles and offer a stable useable capacity of 176.7 Ah L−1 and reach and stable discharge energy densities of 138.91 Wh L−1. Strong bromine binding properties between [C6Py]+ cations and polybromides are confirmed by DFT studies. In contrast to [C2Py]+ electrolytes, the long-chain [C6Py]+ cation in electrolytes has a higher cycling stability or a low decrease in capacity and energy density.

Palladium-Catalyzed Cascade Cyclization/Alkylation of Oxime Ethers: Assembly of 4-Alkylisoxazoles by "Chain-Walking" Strategy.

A reliable and efficient palladium-catalyzed cascade cyclization/alkylation of oxime ethers with unactivated alkenes is described, affording a whole variety of structurally diverse isoxazole derivatives in moderate to good yields with excellent functional group compatibility. Ionic liquid [Aeim]Br not only acts as an environmentally friendly solvent but also acts as an accelerating agent to provide excess bromine source to eliminate bromomethane from oxime ethers. More importantly, the use of "chain-walking" strategy provides a novel methodology in organic synthesis to rapid generation of molecular complexity from readily available starting materials.

Construction and Functionalization of Highly Strained N -Doped Zigzag Hydrocarbon Belts

Construction and Functionalization of Highly Strained <i>N</i> -Doped Zigzag Hydrocarbon Belts

Convenient methods for the synthesis organotellurium compounds derived from pyrazole derivatives: synthesis and antimicrobial evaluation

A new series of organic tellurium compounds containing pyrazole derivatives were prepared. Initially, penta-2,4-dione-3-tellurocyanate (1) was prepared by the refluxing equimolar amounts of potassium tellurocyanate with 3-chloro-2,4-pentadione. Compound 1 was oxidized by excess bromine to obtain the corresponding tribromide (2). The cycloaddition reaction of compound 1 with phenylhydrazine formed 3,5-dimethyl-1-phenyl-4-tellurocyanatopyrazole (3 (in good yield. Treatment of compound 3 with excess bromine gave 3,5-dimethyl-1-phenylpyrazole-4-yltellurium tribromide (4) in an excellent yield. Reduction of compound 3 with a solution of 10% NaOH gave the corresponding ditelluride (5) in excellent yield. Compounds with a general formula of ArTeX3; X = Cl (6) or I (7) were synthesized in excellent yields by reacting compound 3 with excess thionyl chloride or iodine, respectively. Refluxing ditelluride 5 with activated copper powder gave the corresponding telluride (8) in very good yield. Finally, tellurated pyrazole dihalides compounds 9–11 were prepared by reacting 8 with equimoles of the thionyl chloride, bromine and iodine, respectively. The structures of compounds 1–11 were elucidated according to their CHN elemental analyses and FTIR, 1H- and 13C-NMR spectroscopies and mass spectrometry. The antibacterial activity for both Gram-positive and Gram-negative bacteria were evaluated. The tested compounds showed a good degree against the growth of fungi and bacteria. Most the antimicrobial activity of the prepared compounds was better than fluconazole.

Improvement of safe bromine electrolytes and their cell performance in H2/Br2 flow batteries caused by tuning the bromine complexation equilibrium

Hydrogen bromine redox flow batteries utilize bromine electrolytes in their positive half cell, offering capacities larger than 100 Ah L −1 . Addition of quaternary ammonium compounds, so-called bromine complexing agents (BCA), may increase safety as they reduce the vapour pressure of bromine in the posolyte. However, they have not been applied so far. They (a) interact with perfluorosulfonic acid membranes leading to significant reduction of membrane conductivity and (b) they form a low conductive ionic liquid with polybromides, leading to high overvoltage if the formation happens at the electrode. In this work a solution to this problem is proposed by an excess addition of Br 2 to these electrolytes. The excess bromine leads to a permanent bromine fused salt phase in the tank. Bromine formed in the cell stays in the aqueous phase and bromine transfer between the two phases happens in the tank. Transfer of Br 2 without the transfer of [BCA] + cations exists between the phases, while [C2Py] + cations remain in the fused salt and do not influence cell performance. For the first time a posolyte capacity of 179.6 Ah L −1 based on 7.7 M hydrobromic acid with BCA is achieved compared to previous investigations with e.g. 53.9 Ah L −1 . • Evaluation of bromine posolytes with complexing agents (BCA) for energy storage. • Investigation of Br 2 transfer mechanism between aqueous electrolyte and fused salt. • Successful development of electrolyte by intervention in complexation reaction. • Reduced influence of BCA cation on PFSA membrane performance and cell performance. • Increase of the useable electrolyte capacity from 53.9 Ah L −1 to 179.6 Ah L −1 .

Effects of Bromination-Dehydrobromination on the Microstructure of Isotropic Pitch Precursors for Carbon Fibers.

In this work, isotropic pitch precursors are synthesized by the bromination-debromination method with ethylene bottom oil (EO) as the raw material and bromine as the initiator for pitch formation and condensation reactions. The aggregation structure, molecular weight distribution, and molecular structure of isotropic pitch precursors are characterized by thermal mechanical analyzer (TMA), MALDI TOF-MS, and 13C NMR, respectively, for revealing the mechanism of synthesis of isotropic pitch precursors. The results show that at low bromine concentrations, polycyclic aromatic hydrocarbons (PAHs) were mainly ordered in cross-linked structures by bromination-debromination through substitution reactions of side chains. The condensed reactivity can be improved by the effect of bromine, meaning that condensation reaction was aggravated by the method of bromination-dehydrobromination. In the presence of excess bromine, the cross-linked stereo structure of PAHs changed to the planar structure of condensed PAHs, which was not conducive to the subsequent spinning and preparation of carbon fibers.

English

A new spectrophotometric method is described for determination of irbesartan, losartan and bisoprolol in bulk and pharmaceutical dosage forms using insitu generated bromine as oxidizing agent and rhodamine B as chromogenic agent. Drugs are treated with known excess of bromine and residual unreacted bromine is determined by treating with fixed amount of rhodamine B then measuring absorbance at 557nm. The amount of bromine reacted corresponds to the amount of each drug. Effect of acidity, bromate-bromide volume and reaction time, on the absorption were studied. Calibration curves were linear over ranges of and for irbesartan, losartan, and bisoprolol, respectively. The method was satisfactory applied for the determination of drugs in both bulk and pharmaceutical forms and results were compared statistically with reference methods.

Validated and Sensitive Spectrophotometric Method for the Determination of Amitriptyline Hydrochloride

A simple, rapid, selective and highly sensitive spectrophotometric method is described for the quantitative determination of a tricyclic antidepressant drug, amitriptyline hydrochloride (AMT) in pure and in pharmaceutical preparations. The method is based on the bromination of AMT with known excess of bromine. The unreacted bromine is determined based on its ability to bleach the dye Eiochrome blue black R quantitatively at 530 nm. Beer’s law was obeyed over the concentration range 0.0–15 µg/mL. The molar absorptivity value was found to be 1.345×104 L/moL/cm, with the corresponding Sandell’s sensitivity values of 0.0233 µg/cm2. The limits of detection and (LOD) and quantification (LOQ) are also reported for the developed method. Intra- and inter-assay precision and accuracy of the method was established according to the current ICH guidelines. Applications of the procedure to the analysis of various pharmaceutical preparations gave reproducible and accurate results. Further, No interferences were observed from excipients and the validity of the method was tested against reference method. Percent of relative recoveries values were 98.57% to 100.52%.

Electrophilic and Nucleophilic Addition Reactions of α,β-Unsaturated Diphenylphosphoryl Compounds

Procedures were developed for the synthesis of diphenyl(prop-1-en-1-yl)phosphine oxide and cyclohex-1-en-1-yl(diphenyl)phosphine oxide by alkaline hydrolysis of triphenyl(prop-1-en-1-yl)phosphonium bromide and cyclohex-1-en-1-yl(triphenyl)phosphonim bromide, respectively. The bromination of diphenyl(vinyl)phosphine oxide, diphenyl(prop-1-en-1-yl)phosphine oxide, and cyclohex-1-en-1-yl(diphenyl)phosphine oxide with excess bromine gave the corresponding 1,2-dibromo derivatives. Dehydrobromination of 1,2-dibromoethyl(diphenyl)phosphine oxide and 1,2-dibromopropyl(diphenyl)phosphine oxide with sodium hydroxide afforded 1-bromoethenyl(diphenyl)phosphine oxide and 1-bromoprop-1-en-1-yl(diphenyl)phosphine oxide. Addition of bromine and methanol to 1-bromoethenyl(diphenyl)phosphine oxide and 1-bromoprop-1-en-1-yl-(diphenyl)phosphine oxide was studied.

Gold(I) and Gold(III) Complexes of Expanded-Ring N-Heterocyclic Carbenes: Structure, Reactivity, and Catalytic Applications

The oxidative addition of bromine to homo- and heterobis(carbene) gold(I) complexes 1–6 containing expanded-ring N-heterocyclic carbene (erNHC) ligands was explored to prepare the first examples of gold(III) erNHC complexes. The use of stoichiometric amounts of bromine consistently gave clean gold-centered oxidations leading to the isolation of monocarbene and mixed carbene complexes of the type [AuBr3(erNHC)] (7–9) and trans-[AuBr2(iPr2-bimy)(erNHC)]BF4 (13–15), respectively. The use of excess bromine additionally led to ligand brominations in the monocarbene series affording [AuBr3(erNHCBr2)] complexes (10–12), while in the case of the heterobis(carbene) series, tribromide complexes of the type trans-[AuBr2(iPr2-bimy)(erNHC)]Br3 (16–18) were obtained instead. Comparison of the catalytic activities of all complexes in the hydroamination of alkynes revealed the superior performance of mono-erNHC complexes in all cases.

Bromination of 1,2-Dimethylenecyclohexane: Temperature Effect on Product Distribution

In this study the electrophlic addition of bromine to an exocyclic diene, 1,2 dimethylenecyclohexane, was investigated. The bromination of 1,2-dimethylenecyclohexane yielded 1,2-bis(bromomethyl)cylohex-1-en at low temperature. Nevertheless, the bromination of 1,2-dimethylenecyclohexane at room temperature gave 1,4 addition product 1,2-bis(bromomethyl)cylohex-1-en as a main product together with 1-bromo-1-(bromomethyl)-2-methylenecylohexane and 3-bromo-1,2-bis(bromomethyl)cyclohex-1-ene. Similarly, high temperature bromination of 1,2-bismethylenecyclohexane gave the radical bromination products (3-bromo-1,2-bis(bromomethyl)cyclohex-1-ene and 3,6-dibromo-1,2- bis(bromomethyl)cyclohex-1-ene) in addition to the 1,4 addition product. While the bromination of exocylicdiene at room temperature with excess bromine gave tetrabrominated product 1,2-dibromo-1,2-bis(bromomethyl)cyclohexane as a sole product, the bromination of exocyclicdiene in high temperature with excess bromine resulted in a tetra brominated product 1,2-dibromo-1,2-bis(bromomethyl)cyclohexane and the three brominated product 3-bromo-1,2-bis(bromomethyl)cyclohex-1-ene together with the radicalic tetrabrominated product 3,6-dibromo-1,2-bis(bromomethyl)cyclohex-1-ene as main products. However, the high temperature bromination of 1,4 brominated product with excess bromine provided only the radicalic brominated product 3-bromo-1,2-bis(bromomethyl)cyclohex-1-ene and 3,6-dibromo-1,2-bis(bromomethyl)cyclohex-1-ene.Thus the functional agents which can be used as starting material in the synthesis ofmany compounds were synthesized, purified and characterized.

Simultaneous Determination of Concentration and Enantiomeric Composition of Amino Acids in Aqueous Solution by Using a Tetrabromobinaphthyl Dialdehyde Probe.

3,3'-Diformyl-1,1'-bi-2-naphthol or its methoxymethyl-protected derivative is found to undergo a highly selective reaction with excess bromine in CH2 Cl2 at reflux to give the novel 5,5',6,6'-tetrabrominated product (S)- or (R)-2. The observed electrophilic substitution at the 5,5'-positons of an optically active binaphthyl compound is unprecedented. Unlike unbrominated 3,3'-diformyl-1,1'-bi-2-naphthol, which is not suitable for fluorescent recognition in water, compound (S)-2, in combination with Zn2+ , exhibits a highly enantioselective fluorescent response toward amino acids in aqueous solution (HEPES buffer, pH 7.4). It is further found that the condensation product of (R)-2 with tryptophan, (R)-3, shows dual-responsive emissions toward amino acids; the short wavelength (λ1 =350 nm) emission is sensitive to the concentration of the substrate regardless of the chiral configuration and the long wavelength (λ2 >500 nm) emission is highly enantioselective. Thus, the use of (R)-3 allows the simultaneous determination of the concentration and enantiomeric composition of an amino acid sample from one fluorescence measurement.

Maximizing Property Tuning of Phosphorus Corrole Photocatalysts through a Trifluoromethylation Approach.

An eight-member series of CF3-substituted difluorophosphorus corroles was prepared for establishing a structure-activity profile of these high-potential photosensitizers. It consisted of preparing all four possible isomers of the monosubstituted corrole and complexes with 2-, 3-, 4-, and 5-CF3 groups on the macrocycle's periphery. The synthetic pathway to these CF3-substituted derivatives, beginning with (tpfc)PF2, involves two different initial routes: (i) direct electrophilic CF3 incorporation using FSO2CF2CO2Me and copper iodide, or (ii) bromination to achieve the 2,3,8,17,18-pentabrominated compound using excess bromine in methanol. Crystallographic investigations revealed that distortion of the original planar macrocycle is evident even in the monosubstituted case and that it becomes truly severe for the penta-CF3-substituted derivative 5. There is a shift in redox potentials of about 193 mV per -CF3 group, which decreases to only 120 mV for the fifth one in 5. Differences in the electronic spectra suggest that the Gouterman four orbital model decreases in relevance upon gradual -CF3 substitution, a conclusion that was corroborated by DFT calculations. The very significant energy lowering of the frontier orbitals suggested that photoexcitation should lead to a highly oxidizing photocatalyst. This hypothesis was proven true by finding that the most synthetically accessible CF3-substituted derivative is an excellent catalyst for the photoinduced conversion of bromide to bromine (phenol, toluene, and benzene assay).

Simple and Selective Titrimetric and Spectrophotometric Methods for the Determination of Loratadine Using Bromate-Bromide, Methyl Orange and Methylene Blue

One indirect titrimetric and two indirect visible spectrophotometric methods were described for the determination of loratadine in bulk drug and in its formulations. The methods used bromate-bromide, methyl orange and methylene blue as reagents. In titrimetry (method A), loratadine was treated with a known excess of bromate-bromide mixture in acidic medium and the residual bromine was back titrated iodometrically after the reaction between loratadine and in situ bromine was ensured to be complete. In spectrophotometric methods, the excess of bromine was estimated by treating with a fixed amount of either methyl orange (method B) and measuring the absorbance at 520 nm or methylene blue (method C) and measuring the absorbance at 680 nm. In all the methods, the amount of reacted bromine corresponded to the loratadine content. Titrimetric method was applicable over 1-8 mg range and the calculations were based on a 1:0.666 (loratadine:bromate) stoichiometric ratio. In spectrophotometry, the calibration graphs were found to be linear over 150- 350 and 1.75-3.5 μg mL-1 for method B and method C, respectively, with corresponding molar absorptivity values of 9.15 × 102 and 1.10 × 105 L mol-1 cm-1. Accuracy and precision of the assays were determined by computing the intra-day and inter-day variations at three different levels of loratadine. The methods were successfully applied to the assay of loratadine in tablet preparations and the results were compared with those of a reference method by applying Student’s t and F-tests. No interference was observed from common pharmaceutical excipients. The reliability of the methods was further ascertained by performing recovery tests by standard addition method

PH‐Switchable Water‐Soluble Boron Nitride Nanotubes

AbstractThe first example of aqueous solutions of boron nitride nanotubes (BNNTs) with switchable stability and without use of surfactants is demonstrated. The as‐produced boron nitride nanotubes are both purified and solubilized through an environmentally friendly and scalable approach using water extraction and liquid bromine treatment. This treatment effectively removes elemental boron particles and excess bromine reacts with BNNTs, inducing B−N bond cleavage on the BNNT surface to yield hydroxyl (OH) and amino (NH2) functionalized BNNTs. The resulting functionalized BNNTs form stable aqueous solutions around neutral pH (4 &lt; pH &lt; 8), but readily precipitate in other pH ranges. This switchable solubility is explained in terms of the capability of the functional groups (OH and NH2) to form hydrogen‐bonding networks in water. Further, the solubility differences in selected polar organic solvents have been utilized to prepare functionalized BNNTs with higher purity.

Hypoglycemic Agents: Micro-Determination by Highly Sensitive and Validated Spectrophotometric Techniques

The objectives of our present study is to analyse the hypoglycemic agents, Linagliptin (LNG) and Alogliptin (ALG) in pure and bulk forms by simple, reproducible and highly sensitive spectrophotometric assays with detection at 530 (method A) and 520 nm (method B). The methods developed are based on the bleaching of above drugs with known excess of bromine. The unreacted bromine is determined based on its ability to bleach the dye Eriochrome blue black R (method A) and methyl red (method B) quantitatively at 530 (method A) and 520 nm (method B) for both the drugs obeying Beer’s law in the range, 0.0-10.0 and 0.0-8.0 μg ml-1 in both the methods A and B for LNG and ALG, respectively. The values of molar absorptivity were found to be 1.53 × 104 and 2.51 × 104 l mol-1 cm-1 in method A and 1.64 × 104 and 2.82 × 104 l mol-1 cm-1 in method B, respectively with the corresponding Sandell’s sensitivity values 0.0217 and 0.0188 μg cm-2 in method A and 0.0207 and 0.0167 μg cm-2 in method B. According to the current ICH guidelines, various validation parameters of proposed techniques were confirmed by applying the standard addition technique and the results were evaluated in terms of Student’s t-test and variance ratio F-test to find out the significance of proposed methods over the earlier reported methods.

Postsynthetic Addition of Ligand Struts in Metal-Organic Frameworks: Effect of Syn/Anti Addition on Framework Structures with Distinct Topologies.

For the parent metal-organic framework (MOF) of UiO-type 1, postsynthetic bromination (anti addition) was readily carried out on the stilbene-ligand struts by directly adding excess bromine, whereas successful hydrogenation (syn addition) can only be achieved by slowing the reaction rate; otherwise, the crystalline structure of 1 will be irreversibly damaged. Meanwhile, Kagomé-like MOF 2 can be smoothly modified by both postsynthetic bromination and hydrogenation. This study of the structural conversion not only represents the first example that adopts postsynthetic hydrogenation for modifying MOFs but also reveals various factors such as the reaction manner of syn/anti, framework topology, and reaction rate that can influence postsynthetic modification on the ligand struts of MOFs.

Simple regioisomeric differentiation of 2-, 3- and 4-methyl-α-pyrrolidinobutiophenones by gas chromatography–mass spectrometry using bromination

A simple method for the differentiation of three cathinone-type regioisomers, 2-, 3- and 4-methyl-α-pyrrolidinobutiophenone (MePBPs), using a bromination procedure was developed in this study. The bromination was performed in a vial where isomers of MePBP, iron(III) bromide, and liquid bromine were added. After excess bromine in the vial was evacuated and an alkaline solution was added, the compounds were extracted with n-hexane and analyzed by gas chromatography–mass spectrometry. This method is a useful way to differentiate among isomers of MePBPs using the differences in the number of peaks generated and the intensity ratio between peaks on the extracted ion chromatograms. This method seems to have great potential to be applied to regioisomer differentiation of other drugs.

The addition of halogens and interhalogens on palladacyclopentadienyl complexes bearing quinolyl-thioether as spectator ligands. A kinetic and computational study

We have studied the oxidative addition of halogens (I2 and Br2) and interhalogens (ICl and IBr) on complexes of the type [Pd(thioquinoline)C4(COOMe)4], (thioquinoline=8-(methylthio)quinoline, 8-(t-butylthioquinoline, 2-methyl-8-(methylthio)quinoline, 2-methyl-8-(t-butylthio)quinoline).The expected palladium(thioquinoline)-σ-butadienyl derivatives have been obtained by the stoichiometric addition of I2 and Br2 to a solution of the starting palladacyclopentadienyl complexes. The bromine in excess induces the extrusion of the di-bromo-(E, E)-σ-butadiene and the formation of the thioquinoline palladium(II) di-bromide species. The kinetics and mechanism of these reactions have been determined.Except for one case which was analyzed in detail by a computational study, the oxidative addition of the interhalogens ICl and IBr yields the species that is less predictable from the thermodynamic point of view. In general the computational approach justifies the reaction progress and allows an interpretative clue suggesting a kinetically governed path to the reaction products.Finally, the solid state structures of two reaction products were resolved and reported.