Due to the endocrine toxicity,neurotoxic,and reproductive toxicity to organisms,the sources and risks of brominated organic pollutants have attracted widespread attention.However,knowledge gaps remain in the brominati...Due to the endocrine toxicity,neurotoxic,and reproductive toxicity to organisms,the sources and risks of brominated organic pollutants have attracted widespread attention.However,knowledge gaps remain in the bromination processes of emerging phenolic pollutants in plants,whichmay increase the potential health risk associated with food exposure.Our study discovered that light induced generation and accumulation of more toxic brominated organic compounds(Br-org)in lettuce leaves under the stress of acetaminophen(ACE)than that without light,as evidenced by an increase in C-Br bond intensity in FTIR analysis.This result can be explained by the oxidation of bromide ions(Br^(-))by reactive species(ROS and ^(3)Chl*)of chloroplast into reactive bromine species(RBS).The main mechanism is that the redox of Br^(-)reduced the oxidative damage of ACE to the structure and function of chloroplasts,providing good conditions for light energy uptake and utilization and promoting the increase of pigments and active species.Compared with the dark group exposed to 5 mg/L Br^(-),the pigment content,H_(2)O_(2) and ^(1)O_(2) level of the light group increased by 56%,84% and 69%,respectively.On the other hand,RBS attacks certain electrophilic organic compounds in leaves to generate Br^(-)org.Triple excited state of chlorophyll(^(3)Chl^(*))was the dominant species for the transformation of ACE,while RBS is a key factor in the generation of Br-org in the Br^(-)/light/chlorophyll system.A total of six transformation products were identified by HPLC-MS/MS,which were involved in three transformation pathways:methylation,hydroxyl oxidation and hydroxylation followed by bromination.This is the first report that Br^(-)could enter the chloroplast and improved chloroplast structure under ACE stress,and elucidated the bromination mechanism of organics in terrestrial plant involving of biophotochemical bromination in chloroplast besides enzyme-catalyzed bromination.This study is beneficial for risk assessment and prevention of emerging phenolic pollutants.展开更多
Introducing heavy halogen atoms into organic small molecules is a practical strategy for efficient singlet oxygen(^(1)O_(2))generation.Generally,bromine or iodine atoms are introduced on the aza-borondipyrromethene(az...Introducing heavy halogen atoms into organic small molecules is a practical strategy for efficient singlet oxygen(^(1)O_(2))generation.Generally,bromine or iodine atoms are introduced on the aza-borondipyrromethene(aza-BODIPY)core,rather than on the periphery aryl rings for efficient~1O_(2) generation.Herein,an aza-BODIPY dye NBDPBr with unexpected bromination on the periphery aryl rings was synthesized for photoacoustic(PA)imaging-guided synergistic photothermal therapy(PTT)and photodynamic therapy(PDT)in tumor cells.Owing to unexcepted bromination at the periphery aryl rings,NBDPBr demonstrated an outstanding singlet oxygen quantum yield(Φ_(Δ))of 66% which was superior to similar brominated photosensitizers previously reported.After encapsulation with amphiphilic polymer F-127,hydrophilic NBDPBr nanoparticles(NPs)were fabricated and exhibited an excellent photothermal conversion efficiency(η)of 43.0% under 660 nm photoirradiation.In vivo PA imaging results demonstrated that NBDPBr NPs could specifically accumulate at tumor sites and realized the maximum tumor retention at 7 h post-injection.All the in vitro and in vivo results indicated the significant potence of NBDPBr with unexpected bis-bromination for PA imaging-guided synergetic PDT/PTT.展开更多
A series of α-bromoarylethanones were prepared in high yields by a practical and efficient method. The arylethanones were reacted with bromine to give a mixture of α- and α, α-dibromides, which were debrominated w...A series of α-bromoarylethanones were prepared in high yields by a practical and efficient method. The arylethanones were reacted with bromine to give a mixture of α- and α, α-dibromides, which were debrominated with diethylphosphite in the presence of triethylamine to give the desired α-monobromo products.展开更多
Homogeneous isotropic pitches with high softening points were prepared from vacuum-distilled heavy residue ethylene tar(ET-HR)by a two-step method of bromination and subsequent dehydrobromination/polycondensation.The ...Homogeneous isotropic pitches with high softening points were prepared from vacuum-distilled heavy residue ethylene tar(ET-HR)by a two-step method of bromination and subsequent dehydrobromination/polycondensation.The ET-HR was first brominated at 30 or 200℃,and then heat-treated at 350℃to enable the dehydrobromination/polycondensation reactions.GC/MS and LDI TOF/MS spectra indicated that the ET-HR was mainly composed of compounds containing 3-to 6-ring aromatic species with a considerable aliphatic chain content.Compared with thermal condensation alone,such a two-step method increased the softening point of the pitches from 152 to 264℃with a yield in the range of 62 wt.%-67 wt.%and a coking value in the range of 57 wt.%-77 wt.%,depending on the bromination temperature and the bromine content.Structural characterization of the as-prepared pitches by elemental analysis,1H NMR,FT-IR and LDI-TOF/MS showed increased aromatization and polymerization of the precursor during the dehydrobrominatio/polycondensation.All the homogeneous isotropic pitches showed an ability to transform into an anisotropic texture after coking at 800℃.展开更多
The selective brominations of 3, 4-dimethoxytoluene with N-bromosuccinimide were reported. The nuclear and side-chain brominated products were obtained under different reaction conditions. The mechanism was also discu...The selective brominations of 3, 4-dimethoxytoluene with N-bromosuccinimide were reported. The nuclear and side-chain brominated products were obtained under different reaction conditions. The mechanism was also discussed.展开更多
An aqueous solution of hydrogen peroxide and hydrogen bromide illuminated by a 60 W incandescent light bulb serves as a source of bromine radicals.Various substituted toluenes（NO2,Cl,Br,H,CH3） were high selectively ...An aqueous solution of hydrogen peroxide and hydrogen bromide illuminated by a 60 W incandescent light bulb serves as a source of bromine radicals.Various substituted toluenes（NO2,Cl,Br,H,CH3） were high selectively brominated at the benzyl position for monobromination in CH2C12 at ice water with catalyst free.This simple but effective bromination of toluene derivatives with an aqueous H2O2-HBr system is characterized with the use of inexpensive reagents and a lower impact on the environment, which make it a good alternative to the existing bromination methods.展开更多
Mild and efficient method for bromination of electron-rich aromatic compounds is described using polyvinylpolypyrrolidone- bromine complex （PVPP-Br2）. The reaction proceeded smoothly with phenols and N.N-alkylated a...Mild and efficient method for bromination of electron-rich aromatic compounds is described using polyvinylpolypyrrolidone- bromine complex （PVPP-Br2）. The reaction proceeded smoothly with phenols and N.N-alkylated amines to afford the correspond- ing monobrominated product in good yields at ambient temperature.展开更多
An efficient and mild protocol for bromination of aryl azides with N-bromosuccinimide（NBS） under FeCl_3 catalysis in 1,2- dichloroethane was developed.It is proved to be an efficient method for obtaining brominated ...An efficient and mild protocol for bromination of aryl azides with N-bromosuccinimide（NBS） under FeCl_3 catalysis in 1,2- dichloroethane was developed.It is proved to be an efficient method for obtaining brominated aryl azides.展开更多
Rh/SiO2 was prepared for the oxidative bromination of methane. The catalyst was prepared by calcination at different temperatures and for different times to obtain catalysts with different specific surface areas for t...Rh/SiO2 was prepared for the oxidative bromination of methane. The catalyst was prepared by calcination at different temperatures and for different times to obtain catalysts with different specific surface areas for the purposes of producing either CH3Br or CH3Br and CO. It was found that the catalyst having a low specific surface area （calcined at relatively high temperature） favors the selective oxidation of methane to prepare CH3Br, while the catalyst having a high specific surface area favors the deeper partial oxidation of methane, which is good for CH3Br and CO preparation, The 650 h on stream life-time test revealed that the catalytic performance of the 0.4Rh/SiO2-900-10 catalyst was excellent. Both methane conversion and CH3Br selectivity kept increasing trends during the life-time test. No matter how serious was the Rh leaching during the reaction, the 0.4Rh/SiO2-900-10 catalyst did not deactivate at all.展开更多
Halogenated aromatic compounds have attracted increasing concerns due to their toxicity and persistency in the environment, and dehalogenation is one of the promising treatment and detoxification methods. Herein, we s...Halogenated aromatic compounds have attracted increasing concerns due to their toxicity and persistency in the environment, and dehalogenation is one of the promising treatment and detoxification methods. Herein, we systematically studied the debromination efficiency and mechanism of para-bromophenol（4-BP） by a recently developed UV/sulfite process. 4-BP underwent rapid degradation with the kinetics accelerated with the increasing sulfite concentration, pH（6.1–10） and temperature, whereas inhibited by dissolved oxygen and organic solvents. The apparent activation energy was estimated to be 27.8 kJ/mol. The degradation mechanism and pathways of 4-BP were explored by employing N2O and nitrate as the electron scavengers and liquid chromatography/mass spectrometry to identify the intermediates. 4-BP degradation proceeded via at least two pathways including direct photolysis and hydrated electron-induced debromination. The contributions of both pathways were distinguished by quantifying the quantum yields of 4-BP via direct photolysis and hydrated electron production in the system. 4-BP could be readily completely debrominated with all the substituted Br released as Br-, and the degradation pathways were also proposed. This study would shed new light on the efficient dehalogenation of brominated aromatics by using the UV/sulfite process.展开更多
The toluene oxidative bromination reaction catalyzed by hollow titanium silicalite(HTS)zeolite in aqueous medium was investigated by employing H2O2 and HBr under mild conditions without the need for organic solvent.A ...The toluene oxidative bromination reaction catalyzed by hollow titanium silicalite(HTS)zeolite in aqueous medium was investigated by employing H2O2 and HBr under mild conditions without the need for organic solvent.A high toluene conversion(90.7%)and high selectivity of mono-bromotoluene(99.0%)was achieved under the optimal reaction conditions.The UV-Raman spectroscopy was applied for the mechanism study and the result reveals that HTS is efficient for catalyzing the oxidation reaction of HBr with H2O2 to produce abundant active bromine species,which can further facilitate the toluene electrophilic bromination reaction.A two-step toluene bromination reaction mechanism involving the HTS catalyzed active bromine species“generation-conversion-utilization”process is proposed based on the UV-Raman spectroscopy analysis.展开更多
Aromatic bromides are important chemicals in nature and chemical industries.However,their tra‐ditional synthesis routes suffer from low atomic economy and pollutant formation.Herein,we show that organic-inorganic hyb...Aromatic bromides are important chemicals in nature and chemical industries.However,their tra‐ditional synthesis routes suffer from low atomic economy and pollutant formation.Herein,we show that organic-inorganic hybrid perovskite methylammonium lead bromide(MAPbBr_(3))nanocrystals stabilized in aqueous HBr solution can achieve simultaneous aromatic bromination and hydrogen evolution using HBr as the bromine source under visible light irradiation.By hybridizing MAPbBr_(3) with Pt/Ta_(2)O_(5) and poly(3,4‐ethylenedioxythiophene)polystyrene sulfonate as electron‐and hole‐transporting motifs,aromatic bromides were achieved from aromatic compounds with high yield(up to 99%)and selectivity(up to 99%)with the addition of N,N‐dimethylformamide or its analogs.The mechanistic studies revealed that the bromination proceeds via an electrophilic attack pathway and that HOBr may be the key intermediate in the bromination reaction.展开更多
A combination of HBr and trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane as anew and powerful oxidant was found effective for facile brotnination of different aromatic compounds at room temperature in water as a gr...A combination of HBr and trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane as anew and powerful oxidant was found effective for facile brotnination of different aromatic compounds at room temperature in water as a green solvent.Mild reaction conditions,high selectivity and yield,high reaction rate and non-toxicity are some of the major advantages of this synthetic protocol.展开更多
A slow bromination process of butyl rubber （IIR） suffers from low efficiency and low selectivity （S） of target-product. To obtain suitable approach to intensify the process, effects of assistant solvents and mixin...A slow bromination process of butyl rubber （IIR） suffers from low efficiency and low selectivity （S） of target-product. To obtain suitable approach to intensify the process, effects of assistant solvents and mixing inten-sity on the bromination process were systemically studied in this paper. The reaction process was found constantly accelerated with the increasing dosage and polarity of assistant solvent. Hexane with 30%（by volume） dichloro-methane was found as the suitable solvent component, where the stable conversion of 1,4-isoprene transferring to target product （xA1s） of 80.2%and the corresponding S of 91.2%were obtained in 5 min. The accelerated reaction process was demonstrated being remarkably affected by mixing intensity until the optimal stirring rate of 1100 r＆#183;min-1 in a stirred tank reactor. With better mixing condition, a further intensification of the process was achieved in a ro-tating packed bed （RPB） reactor, where xA1s of 82.6% and S of 91.9% were obtained in 2 min. The usage of the suitable solvent component and RPB has potential application in the industrial bromination process intensification.展开更多
Two oxo-vanadium（IV） complexes, [VO（C2O4）（2,2′-bipy）（H2O）]·C2H5OH（1） and VO（C2O4）（phen）（H2O） （2）, where 2,2′-bipy=2,2′-bipyridyl, phen=1,10-phenanthroline, were synthesized as potential funct...Two oxo-vanadium（IV） complexes, [VO（C2O4）（2,2′-bipy）（H2O）]·C2H5OH（1） and VO（C2O4）（phen）（H2O） （2）, where 2,2′-bipy=2,2′-bipyridyl, phen=1,10-phenanthroline, were synthesized as potential functional models of vanadium haloperoxidases（VHPOs） in mixed solvent of ethanol and water at room temperature. The complexes were characterized by elemental analysis, infrared（IR）, UV-Vis and X-ray crystallography. Structural analyses showed that vanadium atom was coordinated by a terminal oxygen, one oxygen atom from coordinated water, two oxygen atoms from the carboxylate group of oxalic acid, and two nitrogen atoms（N1 and N2） from 2,2′-bipy/phen. Central vanadium atoms in complexes 1 and 2 were both in a distorted-octahedral environment, and some intermolecular hydrogen bonding linkages were also observed in each complex. Bromination reaction activity of the two complexes was evaluated with phenol red as organic substrate in the presence of H2O2, Br-and phosphate buffer, indicating that they can be considered as a potential functional model of VHPO. In addition, thermal analysis was also performed and discussed in detail.展开更多
A novel bromination of α,β-unsaturated carboxylic acids was developed via a decarboxylation by virtue of a direct anodic electro-oxidation.In this method,ammonium bromide was employed as a bromine source and the rea...A novel bromination of α,β-unsaturated carboxylic acids was developed via a decarboxylation by virtue of a direct anodic electro-oxidation.In this method,ammonium bromide was employed as a bromine source and the reaction features transition-metal-free,short time,and no additional supporting electrolyte.展开更多
We conducted thermal tests using the reagent tetrabromobisphenol A (TBBPA) and various Pd compounds to study the chemical forms of Pd obtained during the pyrolytic and oxidative decomposition of TBBPA. Thermal testing...We conducted thermal tests using the reagent tetrabromobisphenol A (TBBPA) and various Pd compounds to study the chemical forms of Pd obtained during the pyrolytic and oxidative decomposition of TBBPA. Thermal testing was conducted in an electric furnace at temperatures of 280°C - 800°C in an Ar or Ar-O2 (5%) atmosphere for a heating period of 40 min. Scanning electron microscopy-energy dispersive X-ray spectroscopy results revealed that Pd bromide was formed in the mixture of TBBPA and PdO after heating to 450°C in the Ar atmosphere. In addition, thermogravimetry-differential thermal analysis showed that as the heating temperature was increased from 350°C to 730°C, weight loss occurred at a nearly constant rate, indicating that Pd bromide decomposed in this temperature range.展开更多
In this study, a new method of synthesis of polyethylene glycol supported potassium tribromide （PEG KBr3） and its application in acylation and bromination reactions are reported. Ammonium persulphate oxidizes I（Br ...In this study, a new method of synthesis of polyethylene glycol supported potassium tribromide （PEG KBr3） and its application in acylation and bromination reactions are reported. Ammonium persulphate oxidizes I（Br to the corresponding tribromide which is entrapped by polyethylene glycol leading to stable PEG KBr3. The reagent is proved to be highly efficient for the acylation of variety of alcohols and bromination of activated aromatic substrates. The method is a mild, one pot reaction and involves no use of toxic reagents.展开更多
The new chromium （VI） oxidizing reagent isoquinolinium bromochromate （IQBC） was prepared and characterized. The IQBC has been found to be stable and an efficient solid reagent which can be easily prepared in good ...The new chromium （VI） oxidizing reagent isoquinolinium bromochromate （IQBC） was prepared and characterized. The IQBC has been found to be stable and an efficient solid reagent which can be easily prepared in good yield. It act as an efficient brominating reagent for hydroxylated aromatic compounds as well as good oxidizing reagent for the conversion of alcohols to carbonyl compounds in good to excellent yield. The synthesized isoquinolinium bromochromate is more ideal reagent, with number of specification including： higher yield, mild conditions and easy preparation. The results obtained with isoquinolinium bromochromate are satisfactory and suggest that the reagent has few advantages over the existing chromium （VI） reagents.展开更多
基金supported by the National Natural Science Foundation of China(Nos.42377428 and 42077391)the National Key Research&Developmental Program of China(No.2022YFC3701301)+1 种基金the Shandong Provincial Natural Science Foundation,China(Nos.ZR2020ZD34 and ZR2023YQ031)the Instrument Improvement Funds of Shandong University Public Technology Platform(No.ts20230108).
文摘Due to the endocrine toxicity,neurotoxic,and reproductive toxicity to organisms,the sources and risks of brominated organic pollutants have attracted widespread attention.However,knowledge gaps remain in the bromination processes of emerging phenolic pollutants in plants,whichmay increase the potential health risk associated with food exposure.Our study discovered that light induced generation and accumulation of more toxic brominated organic compounds(Br-org)in lettuce leaves under the stress of acetaminophen(ACE)than that without light,as evidenced by an increase in C-Br bond intensity in FTIR analysis.This result can be explained by the oxidation of bromide ions(Br^(-))by reactive species(ROS and ^(3)Chl*)of chloroplast into reactive bromine species(RBS).The main mechanism is that the redox of Br^(-)reduced the oxidative damage of ACE to the structure and function of chloroplasts,providing good conditions for light energy uptake and utilization and promoting the increase of pigments and active species.Compared with the dark group exposed to 5 mg/L Br^(-),the pigment content,H_(2)O_(2) and ^(1)O_(2) level of the light group increased by 56%,84% and 69%,respectively.On the other hand,RBS attacks certain electrophilic organic compounds in leaves to generate Br^(-)org.Triple excited state of chlorophyll(^(3)Chl^(*))was the dominant species for the transformation of ACE,while RBS is a key factor in the generation of Br-org in the Br^(-)/light/chlorophyll system.A total of six transformation products were identified by HPLC-MS/MS,which were involved in three transformation pathways:methylation,hydroxyl oxidation and hydroxylation followed by bromination.This is the first report that Br^(-)could enter the chloroplast and improved chloroplast structure under ACE stress,and elucidated the bromination mechanism of organics in terrestrial plant involving of biophotochemical bromination in chloroplast besides enzyme-catalyzed bromination.This study is beneficial for risk assessment and prevention of emerging phenolic pollutants.
基金supported by NSF of Jiangsu Province(No.BK20200092)。
文摘Introducing heavy halogen atoms into organic small molecules is a practical strategy for efficient singlet oxygen(^(1)O_(2))generation.Generally,bromine or iodine atoms are introduced on the aza-borondipyrromethene(aza-BODIPY)core,rather than on the periphery aryl rings for efficient~1O_(2) generation.Herein,an aza-BODIPY dye NBDPBr with unexpected bromination on the periphery aryl rings was synthesized for photoacoustic(PA)imaging-guided synergistic photothermal therapy(PTT)and photodynamic therapy(PDT)in tumor cells.Owing to unexcepted bromination at the periphery aryl rings,NBDPBr demonstrated an outstanding singlet oxygen quantum yield(Φ_(Δ))of 66% which was superior to similar brominated photosensitizers previously reported.After encapsulation with amphiphilic polymer F-127,hydrophilic NBDPBr nanoparticles(NPs)were fabricated and exhibited an excellent photothermal conversion efficiency(η)of 43.0% under 660 nm photoirradiation.In vivo PA imaging results demonstrated that NBDPBr NPs could specifically accumulate at tumor sites and realized the maximum tumor retention at 7 h post-injection.All the in vitro and in vivo results indicated the significant potence of NBDPBr with unexpected bis-bromination for PA imaging-guided synergetic PDT/PTT.
文摘A series of α-bromoarylethanones were prepared in high yields by a practical and efficient method. The arylethanones were reacted with bromine to give a mixture of α- and α, α-dibromides, which were debrominated with diethylphosphite in the presence of triethylamine to give the desired α-monobromo products.
文摘Homogeneous isotropic pitches with high softening points were prepared from vacuum-distilled heavy residue ethylene tar(ET-HR)by a two-step method of bromination and subsequent dehydrobromination/polycondensation.The ET-HR was first brominated at 30 or 200℃,and then heat-treated at 350℃to enable the dehydrobromination/polycondensation reactions.GC/MS and LDI TOF/MS spectra indicated that the ET-HR was mainly composed of compounds containing 3-to 6-ring aromatic species with a considerable aliphatic chain content.Compared with thermal condensation alone,such a two-step method increased the softening point of the pitches from 152 to 264℃with a yield in the range of 62 wt.%-67 wt.%and a coking value in the range of 57 wt.%-77 wt.%,depending on the bromination temperature and the bromine content.Structural characterization of the as-prepared pitches by elemental analysis,1H NMR,FT-IR and LDI-TOF/MS showed increased aromatization and polymerization of the precursor during the dehydrobrominatio/polycondensation.All the homogeneous isotropic pitches showed an ability to transform into an anisotropic texture after coking at 800℃.
文摘The selective brominations of 3, 4-dimethoxytoluene with N-bromosuccinimide were reported. The nuclear and side-chain brominated products were obtained under different reaction conditions. The mechanism was also discussed.
基金This project was supported by the National Natural Science Foundation of Zhejiang Province(No.Y407306)the National Natural Science Foundation of China(No.20876148)
文摘An aqueous solution of hydrogen peroxide and hydrogen bromide illuminated by a 60 W incandescent light bulb serves as a source of bromine radicals.Various substituted toluenes（NO2,Cl,Br,H,CH3） were high selectively brominated at the benzyl position for monobromination in CH2C12 at ice water with catalyst free.This simple but effective bromination of toluene derivatives with an aqueous H2O2-HBr system is characterized with the use of inexpensive reagents and a lower impact on the environment, which make it a good alternative to the existing bromination methods.
基金the Research Council of Islamic Azad University-Ayatollah Amoli Branch for financial support of this work
文摘Mild and efficient method for bromination of electron-rich aromatic compounds is described using polyvinylpolypyrrolidone- bromine complex （PVPP-Br2）. The reaction proceeded smoothly with phenols and N.N-alkylated amines to afford the correspond- ing monobrominated product in good yields at ambient temperature.
基金supported by National Natural Science Foundation of China(No30873153)the Key Projects of Shanghai in Biomedical(No08431902700)the Scientific Research Foundation of State Education Ministry for the Returned Overseas Chinese Scholars
文摘An efficient and mild protocol for bromination of aryl azides with N-bromosuccinimide（NBS） under FeCl_3 catalysis in 1,2- dichloroethane was developed.It is proved to be an efficient method for obtaining brominated aryl azides.
基金supported by the Chinese Ministry of Education Project No.107132the Chinese Ministry of Science and Technology Project No.2005CB221406, 2006BAE02B05
文摘Rh/SiO2 was prepared for the oxidative bromination of methane. The catalyst was prepared by calcination at different temperatures and for different times to obtain catalysts with different specific surface areas for the purposes of producing either CH3Br or CH3Br and CO. It was found that the catalyst having a low specific surface area （calcined at relatively high temperature） favors the selective oxidation of methane to prepare CH3Br, while the catalyst having a high specific surface area favors the deeper partial oxidation of methane, which is good for CH3Br and CO preparation, The 650 h on stream life-time test revealed that the catalytic performance of the 0.4Rh/SiO2-900-10 catalyst was excellent. Both methane conversion and CH3Br selectivity kept increasing trends during the life-time test. No matter how serious was the Rh leaching during the reaction, the 0.4Rh/SiO2-900-10 catalyst did not deactivate at all.
基金supported by the National Natural Science Foundation of China(No.21307057)the Natural Science Foundation of Jiangsu Province(No.BK20130577)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(SRFDP,No.20130091120014)the Fundamental Research Funds for the Central Universities(No.20620140128)
文摘Halogenated aromatic compounds have attracted increasing concerns due to their toxicity and persistency in the environment, and dehalogenation is one of the promising treatment and detoxification methods. Herein, we systematically studied the debromination efficiency and mechanism of para-bromophenol（4-BP） by a recently developed UV/sulfite process. 4-BP underwent rapid degradation with the kinetics accelerated with the increasing sulfite concentration, pH（6.1–10） and temperature, whereas inhibited by dissolved oxygen and organic solvents. The apparent activation energy was estimated to be 27.8 kJ/mol. The degradation mechanism and pathways of 4-BP were explored by employing N2O and nitrate as the electron scavengers and liquid chromatography/mass spectrometry to identify the intermediates. 4-BP degradation proceeded via at least two pathways including direct photolysis and hydrated electron-induced debromination. The contributions of both pathways were distinguished by quantifying the quantum yields of 4-BP via direct photolysis and hydrated electron production in the system. 4-BP could be readily completely debrominated with all the substituted Br released as Br-, and the degradation pathways were also proposed. This study would shed new light on the efficient dehalogenation of brominated aromatics by using the UV/sulfite process.
基金The author thanks for the financial support of SINOPEC Corporation(S413108).
文摘The toluene oxidative bromination reaction catalyzed by hollow titanium silicalite(HTS)zeolite in aqueous medium was investigated by employing H2O2 and HBr under mild conditions without the need for organic solvent.A high toluene conversion(90.7%)and high selectivity of mono-bromotoluene(99.0%)was achieved under the optimal reaction conditions.The UV-Raman spectroscopy was applied for the mechanism study and the result reveals that HTS is efficient for catalyzing the oxidation reaction of HBr with H2O2 to produce abundant active bromine species,which can further facilitate the toluene electrophilic bromination reaction.A two-step toluene bromination reaction mechanism involving the HTS catalyzed active bromine species“generation-conversion-utilization”process is proposed based on the UV-Raman spectroscopy analysis.
文摘Aromatic bromides are important chemicals in nature and chemical industries.However,their tra‐ditional synthesis routes suffer from low atomic economy and pollutant formation.Herein,we show that organic-inorganic hybrid perovskite methylammonium lead bromide(MAPbBr_(3))nanocrystals stabilized in aqueous HBr solution can achieve simultaneous aromatic bromination and hydrogen evolution using HBr as the bromine source under visible light irradiation.By hybridizing MAPbBr_(3) with Pt/Ta_(2)O_(5) and poly(3,4‐ethylenedioxythiophene)polystyrene sulfonate as electron‐and hole‐transporting motifs,aromatic bromides were achieved from aromatic compounds with high yield(up to 99%)and selectivity(up to 99%)with the addition of N,N‐dimethylformamide or its analogs.The mechanistic studies revealed that the bromination proceeds via an electrophilic attack pathway and that HOBr may be the key intermediate in the bromination reaction.
文摘A combination of HBr and trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane as anew and powerful oxidant was found effective for facile brotnination of different aromatic compounds at room temperature in water as a green solvent.Mild reaction conditions,high selectivity and yield,high reaction rate and non-toxicity are some of the major advantages of this synthetic protocol.
基金Supported by the National Natural Science Foundation of China(21176014,20990221,21121064)the Science-Technology Project for Supervisors of Excellent Doctor Degree Thesis of Beijing(20111001001)
文摘A slow bromination process of butyl rubber （IIR） suffers from low efficiency and low selectivity （S） of target-product. To obtain suitable approach to intensify the process, effects of assistant solvents and mixing inten-sity on the bromination process were systemically studied in this paper. The reaction process was found constantly accelerated with the increasing dosage and polarity of assistant solvent. Hexane with 30%（by volume） dichloro-methane was found as the suitable solvent component, where the stable conversion of 1,4-isoprene transferring to target product （xA1s） of 80.2%and the corresponding S of 91.2%were obtained in 5 min. The accelerated reaction process was demonstrated being remarkably affected by mixing intensity until the optimal stirring rate of 1100 r＆#183;min-1 in a stirred tank reactor. With better mixing condition, a further intensification of the process was achieved in a ro-tating packed bed （RPB） reactor, where xA1s of 82.6% and S of 91.9% were obtained in 2 min. The usage of the suitable solvent component and RPB has potential application in the industrial bromination process intensification.
基金Supported by the National Natural Science Foundation of China(No.21071071)the Education Foundation of Dalian City in China(No.2009J21DW004)
文摘Two oxo-vanadium（IV） complexes, [VO（C2O4）（2,2′-bipy）（H2O）]·C2H5OH（1） and VO（C2O4）（phen）（H2O） （2）, where 2,2′-bipy=2,2′-bipyridyl, phen=1,10-phenanthroline, were synthesized as potential functional models of vanadium haloperoxidases（VHPOs） in mixed solvent of ethanol and water at room temperature. The complexes were characterized by elemental analysis, infrared（IR）, UV-Vis and X-ray crystallography. Structural analyses showed that vanadium atom was coordinated by a terminal oxygen, one oxygen atom from coordinated water, two oxygen atoms from the carboxylate group of oxalic acid, and two nitrogen atoms（N1 and N2） from 2,2′-bipy/phen. Central vanadium atoms in complexes 1 and 2 were both in a distorted-octahedral environment, and some intermolecular hydrogen bonding linkages were also observed in each complex. Bromination reaction activity of the two complexes was evaluated with phenol red as organic substrate in the presence of H2O2, Br-and phosphate buffer, indicating that they can be considered as a potential functional model of VHPO. In addition, thermal analysis was also performed and discussed in detail.
基金the National Nature Science Foundation of China(Nos.21472177,21672200,21432009,J1310010)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB20000000)
文摘A novel bromination of α,β-unsaturated carboxylic acids was developed via a decarboxylation by virtue of a direct anodic electro-oxidation.In this method,ammonium bromide was employed as a bromine source and the reaction features transition-metal-free,short time,and no additional supporting electrolyte.
文摘We conducted thermal tests using the reagent tetrabromobisphenol A (TBBPA) and various Pd compounds to study the chemical forms of Pd obtained during the pyrolytic and oxidative decomposition of TBBPA. Thermal testing was conducted in an electric furnace at temperatures of 280°C - 800°C in an Ar or Ar-O2 (5%) atmosphere for a heating period of 40 min. Scanning electron microscopy-energy dispersive X-ray spectroscopy results revealed that Pd bromide was formed in the mixture of TBBPA and PdO after heating to 450°C in the Ar atmosphere. In addition, thermogravimetry-differential thermal analysis showed that as the heating temperature was increased from 350°C to 730°C, weight loss occurred at a nearly constant rate, indicating that Pd bromide decomposed in this temperature range.
基金the Department of Science and Technology,DST,New Delhi,India,for fnancial assistance received through a SERC fast track project(No.SR/FTP/CS-100/2007)
文摘In this study, a new method of synthesis of polyethylene glycol supported potassium tribromide （PEG KBr3） and its application in acylation and bromination reactions are reported. Ammonium persulphate oxidizes I（Br to the corresponding tribromide which is entrapped by polyethylene glycol leading to stable PEG KBr3. The reagent is proved to be highly efficient for the acylation of variety of alcohols and bromination of activated aromatic substrates. The method is a mild, one pot reaction and involves no use of toxic reagents.
文摘The new chromium （VI） oxidizing reagent isoquinolinium bromochromate （IQBC） was prepared and characterized. The IQBC has been found to be stable and an efficient solid reagent which can be easily prepared in good yield. It act as an efficient brominating reagent for hydroxylated aromatic compounds as well as good oxidizing reagent for the conversion of alcohols to carbonyl compounds in good to excellent yield. The synthesized isoquinolinium bromochromate is more ideal reagent, with number of specification including： higher yield, mild conditions and easy preparation. The results obtained with isoquinolinium bromochromate are satisfactory and suggest that the reagent has few advantages over the existing chromium （VI） reagents.
基金We thank the National Natural Science Foundation of China(No.30070888)the Chengdu Diao Pharmaceutical Company for support of this work.
文摘Treatment of lappaconitine 1 with NaIO_4 and Br_2-HOAc at room temperature for 7 h afforded smoothly the bromine-containing derivative 4 in 71% yield.
