Bromination Reaction Research Articles

Time-dependent 3D simulations of tropospheric ozone depletion events in the Arctic spring using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem)

Abstract. Tropospheric bromine release and ozone depletion events (ODEs) as they commonly occur in the Arctic spring are studied using a regional model based on the open-source software package Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). For this purpose, the MOZART (Model for Ozone and Related chemical Tracers)–MOSAIC (Model for Simulating Aerosol Interactions and Chemistry) chemical reaction mechanism is extended by bromine and chlorine reactions as well as an emission mechanism for reactive bromine via heterogeneous reactions on snow surfaces. The simulation domain covers an area of 5040 km×4960 km, centered north of Utqiaġvik (formerly Barrow), Alaska, and the time interval from February through May 2009. Several simulations for different strengths of the bromine emission are conducted and evaluated by comparison with in situ and ozone sonde measurements of ozone mixing ratios as well as by comparison with tropospheric BrO vertical column densities (VCDs) from the Global Ozone Monitoring Experiment-2 (GOME-2) satellite instrument. The base bromine emission scheme includes the direct emission of bromine due to bromide oxidation by ozone. Results of simulations with the base emission rate agree well with the observations; however, a simulation with 50 % faster emissions performs somewhat better. The bromine emission due to bromide oxidation by ozone is found to be important to provide an initial seed for the bromine explosion. Bromine release due to N2O5 was found to be important from February to mid March but irrelevant thereafter. A comparison of modeled BrO with in situ and multi-axis differential optical absorption spectroscopy (MAX-DOAS) data hints at missing bromine release and recycling mechanisms on land or near coasts. A consideration of halogen chemistry substantially improves the prediction of the ozone mixing ratio with respect to the observations. Meteorological nudging is essential for a good prediction of ODEs over the 3-month period.

Safe Scale-Up of anN-Bromosuccinimide Involved Bromination Reaction

Safe Scale-Up of an<i>N</i>-Bromosuccinimide Involved Bromination Reaction

Construction of halogenated graphenes by halogenation of hydrogenated graphene

As important graphene derivatives, halogenated graphenes have attracted lots of attention in recent years. Among halogenated graphenes, fluorographene has been extensively studied while research on other halogenated graphenes are still rare. In this work, chlorinated and brominated graphenes composed of chlorine/bromine and hydrogenated graphene were prepared via halogenation of hydrogenated graphene. Taking into account that hydrogenated graphene is also a kind of special alkane, we referred to the surface chlorination and bromination reactions of sp3 C–H bond in alkane molecules and chlorinated/brominated graphenes as special composites of C–Cl/Br and C–H bonds on graphene substrates were obtained. This work reveals that sp3 C–H bond in the surface of hydrogenated graphene has similar reactivity compared to that in common alkanes and presents new approaches to chlorinated and brominated graphenes though the conversion of reactive sp3 C–H bonds into C–Cl or C–Br bonds is still insufficient.

Effects of Structured Solids on Regioselectivity of Dibromination of Naphthalene

The influence of structured solids (amorphous, lamellar and 3D crystalline) on the regioselectivity of the dibromination of naphthalene using bromine at room temperature has been investigated. The more acidic amorphous catalysts and an acidic clay give rapid reactions and lead to a large preponderance of 1,4-dibromonaphthalene over the 1,5-dibromo compound, while calcined KSF clay, a bentonite material, after a short reaction time gives a small predominance of the 1,5-isomer. Longer reaction times lead to the equilibration of reaction mixtures, which means that the 1,4-isomer eventually predominates in all cases. Based on these observations, it has been possible to devise synthetically useful preparative procedures, involving direct room temperature reactions of bromine with naphthalene, for either 1,4-dibromonaphthalene or 1,5-dibromonaphthalene based on the use of different solids, namely Synclyst 13 and KSF clay, respectively.

Room temperature synthesis of defective cerium oxide for efficient marine anti-biofouling

Mimicking marine algae to prevent marine biofouling on the submerged surface of engineering materials represents an alternative and promising approach to conventional toxic anti-biofouling strategy. Here, a novel CeO2 is synthesized by a simple room temperature approach. The as-synthesized CeO2 with rich oxygen vacancies exhibits significantly higher intrinsic haloperoxidase-like activity than the conventional CeO2 in catalyzing the bromination reaction of organic substrates, with a bromination reaction rate of 0.13 µM min−1 at a concentration of 0.05 mg mL−1. In the presence of Br− and H2O2 oxidant, CeO2 demonstrates significant antibacterial efficacies against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, with a significant antibacterial efficiency of 88% and 90%, respectively. Field tests reveal that the plates containing the defective CeO2 (5 wt.%) can effectively hinder the marine biofouling in open ocean. This work provides a promising approach for the development of effective and green marine inorganic anti-foulants at room temperature. Defective CeO2 demonstrates haloperoxidase-like activity towards the catalytic oxidation of bromide, highlighting the potential application towards marine anti-biofouling.

Manganese/bipyridine-catalyzed non-directed C(sp3)-H bromination using NBS and TMSN3.

A Mn(II)/bipyridine-catalyzed bromination reaction of unactivated aliphatic C(sp3)−H bonds has been developed using N-bromosuccinimide (NBS) as the brominating reagent. The reaction proceeded in moderate-to-good yield, even on a gram scale. The introduced bromine atom can be converted into fluorine and allyl groups.

From Reactive Oxygen Species to Reactive Brominating Species: Fenton Chemistry for Oxidative Bromination

Fenton chemistry (Feᴵᴵ + H₂O₂ → HO•/HOO• + H₂O) generates reactive oxygen species (ROS) that are used for treatment of wastewater and oxidation of organic molecules and play a key role in biological oxidation systems. This study shows that Fenton chemistry can be used for generation of reactive brominating species (RBS) under neutral conditions at room temperature. The in situ RBS are successfully used for three types of oxidative bromination reactions. This green and nonacidic new method addresses the safety and environmental challenges of existing oxidative bromination methods. Additionally, this neutral Fenton–bromide system addresses the long-lasting problem of many functional haloperoxidase mimics that required strong acids for oxidation of bromide ion with hydrogen peroxide. This new green and mild method for generating RBS will significantly benefit the wide applications of brominated organic compounds in organic synthesis and the fine chemical and pharmaceutical industries.

Substrate-Controlled Regioselective Bromination of 1,2-Disubstituted Cyclobutenes: An Application in the Synthesis of 2,3-Disubstituted Cyclobutenones.

Easily available disubstituted cyclobutenes were regioselectively halogenated at the allylic position by means of a reaction with bromine. The regioselectivity of bromination is controlled by the presence of a carbocation-stabilizing group. The prepared disubstituted 3-bromocyclobutenes were converted into the corresponding disubstituted cyclobutenones. On the basis of the performed experiments, the mechanism behind the bromination reaction was also proposed.

A Smart Multifunctional Nanoparticle for Enhanced Near-Infrared Image-Guided Photothermal Therapy Against Gastric Cancer.

BackgroundSurgery is considered to be a potentially curative approach for gastric cancer. However, most cases are diagnosed at a very advanced stage for the lack of typical symptoms in the initial stage, which makes it difficult to completely surgical resect of tumors. Early diagnosis and precise personalized intervention are urgent issues to be solved for improving the prognosis of gastric cancer. Herein, we developed an RGD-modified ROS-responsive multifunctional nanosystem for near-infrared (NIR) imaging and photothermal therapy (PTT) against gastric cancer.MethodsFirstly, the amphiphilic polymer was synthesized by bromination reaction and nucleophilic substitution reaction of carboxymethyl chitosan (CMCh) and 4-hydroxymethyl-pinacol phenylborate (BAPE). Then, it was used to encapsulate indocyanine green (ICG) and modified with RGD to form a smart multifunctional nanoparticle targeted to gastric cancer (CMCh-BAPE-RGD@ICG). The characteristics were determined, and the targeting capacity and biosafety were evaluated both in vitro and in vivo. Furthermore, CMCh-BAPE-RGD@ICG mediated photothermal therapy (PTT) effect was studied using gastric cancer cells (SGC7901) and SGC7901 tumor model.ResultsThe nanoparticle exhibited suitable size (≈ 120 nm), improved aqueous stability, ROS-responsive drug release, excellent photothermal conversion efficiency, enhanced cellular uptake, and targeting capacity to tumors. Remarkably, in vivo studies suggested that CMCh-BAPE-RGD@ICG could accurately illustrate the location and margin of the SGC7901 tumor through NIR imaging in comparison with non-targeted nanoparticles. Moreover, the antitumor activity of CMCh-BAPE-RGD@ICG-mediated PTT could effectively suppress tumor growth by inducing necrosis and apoptosis in cancer cells. Additionally, CMCh-BAPE-RGD@ICG demonstrated excellent biosafety both in vitro and in vivo.ConclusionOverall, our study provides a biocompatible theranostic nanoparticle with enhanced tumor-targeting ability and accumulation to realize NIR image-guided PTT in gastric cancer.

A Rapid and Accurate Non Extractive Procedure For Analyzing Monocrotophos In Environmental Samples By Spectrophotometry

An organophosphorous insecticide monocrotophos is increasingly being utilized in agriculture to control insects on a broad range of crops. In this study a new reaction system using spectrophotometric method for quantitative determination of monocrotophos is proposed. The method is based on the bromination of monocrotophos to form dibromomonocrotophos which react with Potassium iodide-Potassium iodate mixture in the presence of leuco malachite green (LMG) to form a water soluble greenish blue colored complex. The change in absorbance as a criterion of the bromination reaction progress was followed spectrophotometrically. To obtain t he maximum sensitivity the effective reaction variables were optimized. The absorbance maximum was observed at 620 nm. Under optimized experimental conditions calibration graph was linear over the range of 10.0-60.0 µg. The molar absorptivity of the colored system is 3.66×104 L mol-1 cm-1 and sandell’s sensitivity is 0.25×10-2 µg cm-2. The calculated detection limit was 0.44 µg mL-1. The interfering effect of various species was also investigated. The present method was successfully applied to the analysis of monocrotophos in different environmental and water samples.

Polystyrene-supported bromoderivative of 2-pyrrolidone: synthesis, characterization and application in microwave-assisted bromination reactions

A novel, microwave safe and recyclable polymeric reagent was prepared by anchoring bromoderivative of 2-pyrrolidone in the polymer matrix of 3% tetraethyleneglycol diacrylate cross-linked polystyrene. The synthetic utility of the prepared polymeric reagent was demonstrated by the efficient bromination of unsaturated compounds, activated aromatic compounds and also for the α-bromination of ketones under microwave activation. Operational simplicity, moderate to excellent yield of the products, shorter reaction time and dry reaction medium are the foremost attraction of this protocol. Moreover, the synthesized functional polymer was stable under standard laboratory conditions and can be kept for several months without any significant loss of activity.

Facile, Electrochemical Chlorination of Graphene from an Aqueous NaCl Solution.

We report a facile approach to directly chlorinate graphene from an aqueous sodium chloride solution under ambient conditions. By applying a moderate anodic voltage to substrate-supported monolayer graphene, the resultant chlorine radicals generated at the graphene surface enable efficient chlorination: X-ray photoelectron spectrum confirms the formation of C-Cl bonds, and reaction voltage-tunable Cl:C atomic ratios of up to 17% are achieved. In comparison, we find the corresponding electrochemical graphene bromination and iodination reactions much less viable. Electrical and Raman characterizations show substantial p-doping for the chlorinated graphene, yet good basal-plane integrity and electrical properties are maintained. Interference reflection microscopy and pH-dependent experiments next help elucidate the competition between the radical-mediated electrochemical chlorination and oxidation in the process, and rationalize acidic conditions for optimal chlorination. Reaction in a mixed NaCl-NaN3 solution shows the electrochemical chlorination to be fully suppressed by azidation, yet a sequential, two-step chlorination-azidation approach permits facile bifunctionalization.

Synthesis and Photoactivated Toxicity of 2-Thiophenylfuranocoumarin Induce Midgut Damage and Apoptosis in Aedes aegypti Larvae.

Furanocoumarins are photoactive compounds derived from secondary plant metabolites. They possess many bioactivities, including antioxidative, anticancer, insecticidal, and bactericidal activities. Here, we designed a new scheme for synthesizing 2-arylfuranocoumarin derivatives by condensation, esterification, bromination, and Wittig reaction. We found that 2-thiophenylfuranocoumarin (Iy) had excellent photosensitive activity. Three Iy concentrations (LC25, LC50, and LC75) were used to treat the fourth instar larvae of Aedes aegypti (A. aegypti). The photoactivated toxicity, sublethal dose, mitochondrial dysfunction, oxidative stress level, intestinal barrier dysfunction, and apoptosis were studied. The results showed that Iy induced reactive oxygen species (ROS) production in midgut cells under ultraviolet light. Ultrastructural analysis demonstrated that mitochondria were damaged, and the activities of related enzymes were inhibited. Ultimately, Iy exposure led to excessive ROS production followed by the inhibition of antioxidant enzymes, including SOD, CAT, GPx, and GR, which diminished ROS elimination and escalated oxidative stress in midgut cells, aggravating the degree of oxidative damage in these cells. Histopathological changes were observed in the midgut, which led to intestinal barrier dysfunction. When the elimination of ROS was blocked and it accumulated in cells, apoptosis-related genes, including AeDronc, AeCaspase7, and AeCaspase8, were induced and activated. In addition, Iy affected the growth and development of A. aegypti at sublethal concentrations, and there was an obvious post-lethal effect. Thus, we found that Iy caused midgut damage and apoptosis in A. aegypti larvae under ultraviolet light, which preliminarily revealed the mode of action of Iy in A. aegypti.

An Innovative Spectrophotometric Method for the Estimation of H1 Receptor Antagonists in Pharmaceutical Formulations

An innovative, sensitive, simple and rapid method has been developed for estimation of selective H1 receptor antagonist. The method is based on bromination of drug. The proposed spectrophotometric method was developed using potassium bromate-potassium bromide mixture in acidic condition followed by the reaction of surplus bromine with methyl orange dye and measure the absorbance at 506 nm. Beer’s law was obeyed in the concentration range of 0.2-1.2 μg/ml, 0.3-1.7 μg/ml and 0.03-0.18 μg/ml for olopatadine hydrochloride, fexofenadine hydrochloride and azelastine hydrochloride respectively. The method was optimized for concentration of hydrochloride, ml of hydrochloride, ml of potassium bromate-potassium bromide mixture, ml of dye and reaction time. Developed method has been validated in accordance to International Council on Harmonisation guideline Q2R1. Statistical analysis proved that the method is accurate, sensitive, selective, precise and reproducible. The simple procedure with high accuracy, wide linearity range and sensitivity imply that the demonstrated method to be appropriate for routine estimation and quality control assay of pharmaceutical formulations.

Electrohalogenation of organic compounds.

Herein, we present an overview of recent advances in the electrochemical halogenation of organic compounds. Halogen-containing compounds are essential building blocks for post-functionalization in academic research and in different industrial sectors, notably pharmaceutical companies. One of the main advantages of using electrosynthesis is its environmentally-friendly characteristics. Electrosynthesis is recognized as a methodology that can fulfill different criteria of the green chemistry concept and constitutes a promising tool in the development of new procedures in organic synthesis. In this review we target sp, sp2 and sp3 carbon fluorination, chlorination, bromination and iodination reactions using electrolysis as a redox medium. Mechanistic insights and substrate reactivity are also discussed.

Metal-free site-selective C-H cyanoalkylation of 8-aminoquinoline and aniline-derived amides with azobisisobutyronitrile.

Using K2S2O8, an efficient and metal-free site-selective C–H cyanoalkylation of 8-aminoquinoline and aniline-derived amides with AIBN (azobisisobutyronitrile) was developed. Without any catalyst, various substrates and functional groups were compatible to afford corresponding products in moderate to high yields. A mechanism study displayed that a radical–radical coupling process was involved via the N-centered radical generation and delocalization of aryl amides.

Highly emissive fused diarylmaleimides synthesized by a cascade reaction of selective bromination and visible-light-driven cyclization

A simple strategy for constructing fused diarylmaleimides (FAMs) under mild condition is presented through a cascade reaction involving a selective bromination with NBS and a visible-light-driven cyclization under 18 W of LED. Compared with traditional oxidation method, the cascade reaction does not use any oxidant, metal-based catalyst, and ultraviolet rays. According to the strategy, a series of symmetrical and asymmetrical FAMs with different aromatic rings are obtained in high yield up to 96%. Most of FAMs exhibit blue-shifted emission and higher luminescent efficiency (Φf up to 84%) in solution than their open-ring counterparts for the large π-conjugated systems weakening intramolecular charge transfer. Unexpectedly, the fused rings with nearly coplanar do not quench the solid-state fluorescence of FAMs, due to the heteroatoms and peripheral substituents inhibiting molecules forming H-aggregation-like tight packing, resulting in decent quantum yield in solid. Particularly, FAM with indolo [2,3-a] pyrrolo [3,4-c] carbazoles (B3IM-BHc) has unique pores in the crystal structure, which imposes it huge potential as smart florescent material and switch.

SYNTHESIS AND BROMINATION OF BIS-HETERYL DITELLURIDES

It is known from the literature, that organic tellurium compounds have valuable biological properties. One example of such type of compounds is organic ditellurides. There are also known the usage of ditellurides as initiators in the synthesis of polymers, and they are widely used as synthons for the synthesis of another organotellurium compounds. In particular, the halogenation of diarylditellurides leads to the formation of such electrophilic reagents as aryltellurium trihalides, which proved to be suitable substrates for the synthesis of heterocyclic compounds.This paper describes a method for the synthesis of ditellurides, which contain condensed heterocycles of the quinazoline and thienopyrimidine series, by reducing of the corresponding heteryltellurium trichlorides.The interaction of 2-methyl-2-(trichlorotelluromethyl)-2,3-dihydro-5H-thiazolo[2,3-b]quinazolin-5-one hydrochloride with a 4-fold excess of 9-aqueous sodium sulfide in water at room temperature leads to formation of 2,2'-(ditellanidylbis(methylene))bis(2-methyl-2,3-dihydro-5H-thiazolo[2,3-b]quinazolin-5-one) with high yield. The introduction of the trifluoromethyl group at the 8th position of 2-methyl-2-(trichlorotelluromethyl)-2,3-dihydro-5H-thiazolo[2,3-b]quinazolin-5-one hydrochloride increases the yield of the target ditelluride. 2-[(Trichlorotelluro)methyl]-2,3,6,7,8,9-hexahydro-5H-benzo[4,5]thieno[2,3-d]thiazolo[3,2-a]pyrimidin-5-one hydrochloride was used for the study of the impact of the condensed with pyrimidine moiety cycle on the formation of ditellurides in the sodium sulfide reduction reaction and it was stated that under the found conditions it is uniformly converted into 2,2'-(ditellanidylbis(methylene))bis(2,3,6,7,8,9)-hexahydro-5H-benzo[4,5]thieno[2,3-d]thiazolo­[3,2-a]-pyrimidin-5-one).The obtained ditellurides were used in the bromination reaction. It was found that the interaction of the starting ditellurides with a triple excess of bromine in chloroform medium allows obtaining the tribromides of the thiazoloquinazoline and thiazolothienopyrimidine series selectively.Therefore, the hydrochlorides of trichlorotelluromethyl-substituted thiazolinopyrimidines can be reduced to bis heterylditellurides, which under bromination conditions form tribromotelluromethyl-substituted thiazolinopyrimidines.

SYNTHESIS AND BROMINATION OF PROPARGYLIC TRIFLUOROUTIC ACID AMIDE

Carboxylic acid amides are convenient reagents for organic synthesis, and are promising building blocks for obtaining a large number of acyclic and heterocyclic compounds.Among the various aliphatic, aromatic and heterocyclic amides, fluorine-containing derivatives are the least studied. The presence of a carbonyl group, a fluoroalkyl substituent and an alkyl-substituted amino functional groups determines the variety of transformations for this class of compounds. The introduction of an unsaturated alkyl substituent to the amide nitrogen atom and the presence of an additional nucleophilic center of the oxygen or nitrogen atom makes such amides promising for the study of their reactions with electrophilic reagents.The aim of this work is the synthesis of propargyl trifluoroacetic acid amide and the study of its interaction with bromine.Trifluoroacetic acid propargylamide was prepared from trifluoroacetic acid ethyl ester and propargylamine in tetrahydrofuran medium, its structure was confirmed by NMR1H and NMR19F spectra.It is known from the literature sources that the presence of a multiple bond and an additional intramolecular nucleophilic center in propargyl amines and amides creates the pre-conditions for the cyclization reaction under the action of halogen-containing electrophilic reagents. Such structural features are also characteristic for N-propargyltrifluoroacetamide, namely the multiple bond of the propargyl moiety and additional intramolecular nucleophilic centers of nitrogen and oxygen atoms. Under the action of bromine as an electrophilic reagent on N-propargyltrifluoroacetamide, the formation of both the coupling product and the cyclization with the formation of azetidine, oxazoline or oxazine heterocycles is possible.The bromination reaction of N-propargyltrifluoroacetamide was performed in dichloromethane with an equimolar amount of reagents in the presence of potash. According to the spectral data, the coupling product N- (2,3-dibromoprop-2-en-1-yl) trifluoroacetamide is formed, which is confirmed by the NMR1H and NMR19F spectra. The absence of the cyclization process can be explained via the lower nucleophilicity of the oxygen atom compared to sulfur.

Photochemical Radical C-H Halogenation of Benzyl N-Methyliminodiacetyl (MIDA) Boronates: Synthesis of α-Functionalized Alkyl Boronates.

α-Haloboronates are useful organic synthons that can be converted to a diverse array of α-substituted alkyl borons. Methods to α-haloboronates are limiting and often suffer from harsh reaction conditions. Reported herein is a photochemical radical C-H halogenation of benzyl N-methyliminodiacetyl (MIDA) boronates. Fluorination, chlorination, and bromination reactions were effective by using this protocol. Upon reaction with different nucleophiles, the C-Br bond in the brominated product could be readily transformed to a series of C-C, C-O, C-N, C-S, C-P, and C-I bonds, some of which are difficult to forge with α-halo sp2 -B boronate esters. An activation effect of B(MIDA) moiety was found.