Presence Of Bromide Research Articles

Experimental and simulation investigations of UV/persulfate treatment in presence of bromide: Effects on degradation kinetics, formation of brominated disinfection byproducts and bromate

Bromide (Br−), which is omnipresent in water bodies, can not only affect the degradation kinetics of target pollutants but may also form undesired byproducts (such as bromate (BrO3-) and brominated disinfection byproducts (Br-DBPs)) through sulfate radical (SO4∙-)-based advanced oxidation processes (AOPs). This study found that Br− significantly suppressed the degradation of diethyl phthalate (DEP) based on the ultraviolet (UV)/persulfate (PS) treatment and was efficiently converted into reactive species (radicals and free bromine) by the SO4∙- or hydroxyl radical (HO) generated in the UV/PS system. These reactive bromine species could, in turn, brominate the phenolic degradation intermediates of DEP as well as natural organic matter (NOM), yielding Br-DBPs, including tribromomethane (TBM), which was observed when Br−, DEP and/or NOM coexisted in this UV/PS system. However, the Br-DBPs were a short-lived form of bromine during the transformation of Br– and were degraded by the excessive oxidants (e.g., SO4∙- and HO). Instead, Br− was eventually transformed into BrO3-, with free bromine acting as the requisite intermediate. The BrO3- formation initially showed a delay before increasing monotonically. In general, raising the PS dosage and the initial Br− concentrations enhanced both the maximum concentration of TBM and the formation of BrO3-, while increasing the amounts of DEP and NOM facilitated the former and inhibited the latter. The maximum concentration of TBM increased while the formation of BrO3- was suppressed with increasing pH from 5.0 to 8.0. In addition, through simulating the steady-state concentration of radicals, it was found that the contribution of bromine atom radical (Br) towards oxidizing free bromine to BrO3- was far greater than those of SO4∙- and HO. The findings demonstrate the potential negative effects of Br− on SO4∙--based AOPs, which need to be considered when this technology is applied in practice.

Effects of Pre-Oxidation on Haloacetonitrile and Trichloronitromethane Formation during Subsequent Chlorination of Nitrogenous Organic Compounds.

The reaction between organic matter and disinfectants leads to the formation of disinfection byproducts (DBPs) in drinking water. With the improvement of detection technology and in-depth research, more than 1000 kinds of DBPs have been detected in drinking water. Nitrogenous DBPs (N-DBPs) are more genotoxic and cytotoxic than the regulated DBPs. The main methods are enhanced coagulation, pretreatment, and depth technologies which based are on conventional technology. Amino acids (AAs) are widely found in surface waters and play an important role by providing precursors from which toxic nitrogenous disinfection by-products (N-DBPs) are generated in chlorinated drinking water. The formation of N-DBPs, including dichloroacetonitrile, trichloroacetonitrile, and trichloronitromethane (TCNM), was investigated by analyzing chlorinated water using ozone (OZ), permanganate (PM), and ferrate (Fe(VI)) pre-oxidation processes. This paper has considered the control of pre-oxidation over N-DBPs formation of AAs, OZ, PM, and Fe(VI) pre-oxidation reduced the haloacetonitrile formation in the downstream chlorination. PM pre-oxidation decreased the TCNM formation during the subsequent chlorination, while Fe(VI) pre-oxidation had no significant influence on the TCNM formation, and OZ pre-oxidation increased the formation. OZ pre-oxidation formed the lowest degree of bromine substitution during subsequent chlorination of aspartic acid in the presence of bromide. Among the three oxidants, PM pre-oxidation was expected to be the best choice for reducing the estimated genotoxicity and cytotoxicity of the sum of the measured haloacetonitriles (HANs) and TCNM without bromide. Fe(VI) pre-oxidation had the best performance in the presence of bromide.

TRIHALOMETHANE AND HALOACETIC ACID FORMATION POTENTIAL OF TROPICAL PEAT WATER: EFFECT OF TIDAL AND SEASONAL VARIATIONS

The existence of humic substances in peat water impacts the presence of the dissolved organic matter (DOM) which is the precursor of trihalomethanes (THMs) and haloacetic acids (HAAs). However, information on DOM characteristics, THMs and HAAs Formation Potential (THMFP and HAAFP) in tropical peat water are still limited. This study aimed to determine the correlations between DOM, THMFP, and HAAFP during dry and rainy seasons in tropical peat water in Indonesia. Samples of peat water are taken from the water canal and tidally affected river on Sumatera’s peatland during the rainy season and dry season to determine the effects of the seasons and tides. DOM measured by dissolved organic carbon (DOC), specific ultraviolet absorbance and the ratio of E465/E665 while THMFP determined from a total of THMFP4 measurements and HAAFP determined from measurement of total HAAFP5. Compared to dry season, values of all organic parameters on rainy season were higher but fewer in river. Canal water has a higher DOC while river water has a higher chloride and bromide content. Increasing of DOC in the rainy season correlates with increasing of THMFP4 and HAAFP5. THMFP4 is dominated by chloroform on canal while brominated THMs predominate in river water which correlates with the presence of bromide. Chlorinated HAAs dominate HAAFP5 in canal water while brominated HAAs increases in the river. Seasons and tides affect the appearance of bromide contaminants in water that affects the form of THMFP and HAAFP.

Halide-induced dissolution of lead(IV) oxide in frozen solution

The dark dissolution behavior of plattnerite (ß-PbO2) was investigated in frozen solutions containing halide ions and compared with those in aqueous solution. The amount of dissolved lead in the frozen solutions varied depending on the solution pH and the kind and concentration of halide ions. The presence of bromide and iodide ions enhanced the dissolution of lead in the aqueous phase, whereas the effect of chloride was insignificant. Compared with the aqueous phase dissolution, ß-PbO2 dissolution in the frozen solution was slightly enhanced in the presence of bromide but suppressed in the presence of iodide. Iodide ions seemed to be relatively more trapped in the bulk ice (ice-crystal lattice) than bromide ions, which might be related to the suppressed dissolution of lead oxide in the presence of iodide. The co-existence of bromide (or iodide) and chloride ions in the frozen solution enhanced the dissolution of lead, which seems to be enabled by an additional reaction pathway involving the formation of mixed halide radicals, whereas such kind of synergistic enhancements were not observed in aqueous solution. The halide-induced lead oxide dissolution in frozen solutions can be related to the behavior of lead ions found in various media of frozen environments.

Ultrasound Aided Expedient Synthesis, Characterization and Antimicrobial Studies of Fluorenyl-Hydrazono-Thiazole Derivatives

Ultrasound assisted facile synthesis of fluorenyl-hydrazonothiazoles (4a-d) in quantitative yields by the condensation of 2-(9H-fluoren-9-ylidene)hydrazinecarbothioamide (2) with substituted phenacyl bromides in presence of dimethyl formamide has been reported. The reaction of carbothioamide 2 with α-haloacids resulted in to fluorenyl-hydrazonothiazolidin-4-ones (3). The structural characterization of the cyclized products have been established by elemental analysis and spectral data (IR, NMR and mass). The antimicrobial studies of the synthesized compounds are also reported.

Removal of bromide from natural waters: Bromide-selective vs. conventional ion exchange resins

The presence of bromide (Br−) in water results in the formation of brominated disinfection byproducts (DBPs) after chlorination, which are much more cytotoxic and genotoxic than their chlorinated analogs. Given that conventional water treatment processes (e.g., coagulation, flocculation, and sedimentation) fail to remove Br− effectively, in this study, we systematically tested and compared the performance of different anion exchange resins, particularly two novel Br-selective resins, for the removal of Br−. The resins performance was evaluated under both typical and challenging background water conditions by varying the concentrations of anions and organic matter. The overall Br− removal results followed the trend of Purolite-Br ≥ MIEX-Br > IRA910 ≥ IRA900 > MIEX-Gold > MIEX-DOC. Further evaluation of Purolite-Br resin showed Br− removal efficiencies of 93.5 ± 4.5% for the initial Br− concentration of 0.25 mg/L in the presence of competing anions (i.e., Cl−, NO3−, NO2−, SO42−, PO43−, and a mixture of all five), alkalinity and organic matter. In addition, experiments under challenging background water conditions confirmed the selectivity of the resins (i.e. Purolite-Br and MIEX-Br) in removing Br−, with SO42− and Cl− exhibiting the greatest influence upon the resin performance followed by NOM concentration, regardless of the NOM characteristic. After Br− removal, both the subsequent formation of brominated DBPs (trihalomethanes, haloacetic acids, and haloacetonitriles), and the total organic halogens (TOX), decreased by ∼90% under the uniform formation conditions. Overall, Br-selective resins represent a promising alternative for the efficient control of Br-DBPs in water treatment plants.

Underestimated risk from ozonation of wastewater containing bromide: Both organic byproducts and bromate contributed to the toxicity increase

Ozonation is widely used in wastewater treatment but the associated byproduct formation is a concern. When ozonation is used in the presence of bromide, bromate is generally considered as a major byproduct, and few studies have examined the toxicity of organic byproducts. This study was designed to investigate the cytotoxicity, genotoxicity and DNA/RNA oxidative damage to Chinese hamster ovary (CHO) cells of organic extracts from ozonated wastewater in the absence or presence of bromide. Ozonation effectively detoxified secondary effluents containing no bromide. However, ozonation significantly increased the cytotoxicity and genotoxicity of the effluents spiked with a bromide concentration as low as 100 μg/L, compared with the bromide-free effluent. When the bromide concentration in the effluent was increased to 2000 μg/L, ozonation resulted in 1.4–1.5 times the cytotoxicity and 1.5–5.0 times the genotoxicity of the non-ozonated secondary effluent. Besides, the oxidative stress (including reactive oxygen species and reactive nitrogen species) and DNA/RNA oxidative damage also became more severe and a high level of 8-hydroxy-(deoxy)guanosine was detected in the CHO cell nucleus in the presence of bromide. Cytotoxicity and genotoxicity were found to increase with the formation of total organic bromine (TOBr). When the CHO cells were exposed to both the organic byproducts and bromate formed from wastewater containing 500 and 2000 μg/L bromide, bromate significantly increased oxidative stress and DNA/RNA oxidative damage at relatively high concentration factors, suggesting both organic byproduct and bromate can contribute to toxicity increase. During ozonation of the effluent containing bromide, particular attention should be paid to the organic byproducts such as TOBr.

Formation of CX3R-type disinfection by-products during the chlorination of protein: The effect of enzymolysis

It is commonly acknowledged that proteins, comprising a large portion of dissolved organic nitrogen pool, are important precursors of disinfection by-products (DBPs). Moreover, proteins can also undergo degradation (e.g. enzymolysis) in aquatic environment or during biological treatment processes. In this study, a well-characterized protein, bovine serum albumin (BSA) was used as model compound to investigate the effect of enzymolysis on the formation of four classes of CX3R-type DBPs (i.e. trihalomethanes, haloacetaldehydes, haloacetonitriles, and haloacetamides) during chlorination. After enzymolysis, the three-dimension structure of BSA was destroyed, increasing the accessibility of inside amino acids to chlorine, thus enzyme-hydrolysed BSA exhibited higher chlorine demand and higher formation of total organic halogen (TOX) than un-hydrolysed BSA. Generally, enzyme-hydrolysed BSA produced more CX3R-type DBPs, which is due to the facilitation of fragmentation of BSA by enzymolysis. In the presence of bromide, enzymolysis promoted the formation of TOX to a greater extent than in the absence of bromide. The effect of enzymolysis on pre-oxidation efficiency in the control of CX3R-type DBPs was also investigated. It was found that the reduction in CX3R-type DBP formation from chlorinated enzyme-hydrolysed BSA was more significant than that from chlorinated un-hydrolysed BSA, but the former still exhibited higher calculated cytotoxicity than the latter, indicating the removal of CX3R-type DBP precursors was indirectly offset by the effect of enzymolysis. This study provides insights into the effect of the structural transformation of protein during water treatment processes on CX3R-type DBP formation.

Effect of Contact Time of Gaseous Phase in Multi-Stage Contact Columns in Intermediate Ozonation Process on Reduction of Bromate Concentration

This article describes research on the application of ozone technology for the purification of surface water in the presence of bromides. The pilot system used multistage contact columns for water-ozonation processes with stabilized contact time. The research has shown that the basis for limiting the formation of bromates is the optimum amount of residual ozone after the ozonation process and the constant time of ozone contact with the water. This solution allows us to reduce the formation of harmful compounds and apply ozone technology with water containing carcinogenic precursors.

The Contrast between the Pitting Corrosion of 316 SS in NaCl and NaBr Solutions: Part II. Morphology, Chemistry, and Stabilization of the Pits

This paper intends to evaluate the pit chemistry characteristics of 316 austenitic stainless steel in NaCl and NaBr solutions while discussing the pitting transition from metastability to stability. Results reveal that increasing the relative concentration of bromide increases the critical and saturation concentrations of cations, which are, respectively, requisites for pit survival and salt precipitation. Besides, bromide causes the ohmic solution resistance of the pit solution to increase. Consequently, it intensifies the pit transition from metastability to stability and retards the occurrence of the stable pitting. The morphology of the pits and the influence of the pit lacy cover on the pit stabilization in NaCl and NaBr solution are also discussed. It was also observed that contrary to metastable pits, salt-covered stable ones have higher growth kinetics in the presence of bromide.

Application of UVOX Redox® for swimming pool water treatment: Microbial inactivation, disinfection byproduct formation and micropollutant removal

Alternative disinfection technologies may overcome some of the limitations of conventional treatment applied in swimming pools: chlorine-resistant pathogens (e.g. Cryptosporidium oocysts and Giardia cysts) and the formation of chlorinated disinfection byproducts. In this paper, results of full scale validation of an alternative disinfection technology UVOX Redox® (hereinafter referred to as UVOX) that combines ozonation and UV irradiation are presented. The performance was assessed in terms of microbial inactivation, disinfection byproduct formation and micropollutant removal. UVOX was able to achieve 1.4–2.7 log inactivation of Bacillus subtilis spores at water flows between 20 and 76 m³/h. Lower formation of trichloromethane and dichloroacetic acid was observed with UVOX followed by chlorination when compared to chlorination alone. However, due to the use of ozone and the presence of bromide in the pool water, the formation of trihalomethanes and haloacetic acids shifted to more brominated byproducts. Chlorine alone was able to remove the target micropollutants: acetaminophen, atenolol, caffeine, carbamazepine, estrone, estradiol, and venlafaxine (>97% removal) after 24 h, with the exception of ibuprofen (60% removal). The application of UVOX in chlorinated water enhanced the removal of ibuprofen. The application of UVOX could lower the usage of chlorine to the level that provides an adequate residual disinfection effect.

Synthesis, biological evaluation, molecular docking and in silico ADME studies of phenacyl esters of N-Phthaloyl amino acids as pancreatic lipase inhibitors

In continuation of our previous study, a series of phenacyl esters of N-phthaloyl amino acids were synthesized and screened for their in vitro pancreatic lipase inhibitory activity. N-phthloylation of amino acids and subsequent esterification with different phenacyl bromides in presence of N,N-Dimethylformamide (DMF) afforded the corresponding phenacyl esters in quantitative yields. The synthesized compounds were found to have potent in vitro pancreatic lipase inhibitory activity in 0.9–2.5 μM range. The most active compound 2‐(4‐bromophenyl)‐2‐oxoethyl 3‐(1,3‐dioxo‐2,3‐ dihydro‐1H‐isoindol‐2‐yl) propanoate (4g) displayed very good pancreatic lipase inhibitory activity with the IC50 value 0.9 μM. To understand the enzyme inhibition and to ensure the lead likeness, in silico docking and ADME studies were carried on title compounds. The in vitro pancreatic lipase inhibitory activities and in silico studies suggested that this N-phthaloyl phenacyl ester analogues could be a potential lead and may be taken to the next level of antiobesity drug development.

Size Stability Study of Catalytically Active Sub-2 nm Diameter Gold Nanoparticles Synthesized with Weak Stabilizers.

Here we report on the very low size stability of electrocatalytically active 1.5 to 2.0 nm diameter tetrakis(hydroxymethyl)phosphonium chloride-stabilized Au nanoparticles (THPC Au2nm NPs) chemically attached to glass/indium tin oxide electrodes. The potential for oxidative dissolution of THPC Au2nm NPs in the presence of bromide is about 250 mV negative of 4 nm diameter citrate-stabilized Au NPs (Cit Au4nm NPs) and 450 mV negative of bulk Au, which provides us with an easy method to assess the size stability using anodic stripping voltammetry. The THPC Au2nm NPs show a strong CO2 reduction wave at about -0.40 V (vs RHE), which is nonexistent for the Cit Au4nm NPs or bulk Au. The THPC Au2nm NPs are also comparatively more electroactive for the hydrogen evolution reaction. In acid electrolyte, however, the potential for surface Au2O3 formation on THPC Au2nm NPs is significantly negative relative to bulk Au, and a single cycle through the surface oxide and reduction waves leads to an increase in the NP size to about 4 nm. Similarly, the THPC Au2nm NPs undergo Ostwald ripening in the presence of bromide within 5 min at potentials well before oxidation, which increases their size to 4-10 nm in diameter by 35 min. Exposure to ozone for only 1-2 min also causes the THPC Au2nm NPs to increase in size to about 4 nm. In comparison, Cit Au4nm NPs are stable under all of these conditions, requiring much longer times to change in size. These differences in reactivity and size stability are due to the different Au NP size. Sub-2 nm diameter NPs with weak stabilizers are potentially very useful for electrocatalysis, but their low oxidation potential and poor size stability are major issues of concern.

Electrochemical multisensor system for monitoring hydrogen peroxide, hydrogen and oxygen in direct synthesis microreactors

We present an electrochemical microsensor system for the monitoring of hydrogen peroxide, dissolved hydrogen and dissolved oxygen inside a direct synthesis microreactor. The setup allows the online, in situ measurement of high reactant concentrations by amperometric detection of all three reactants in aqueous solution using chronoamperometric protocols. Hydrogen peroxide is a key chemical for industrial oxidation applications, and its catalyzed direct synthesis is an attractive process route. For the first time, we integrated an electrochemical cell into a high pressure stainless steel microreactor environment (pressures up to 100 bar, pH of 3–4 and presence of bromide) by fabricating sensor plugs with 300 μm platinum microelectrodes encapsulated into a robust epoxy housing. The first microfabricated silver/silver bromide pseudo-reference electrode, integrated by electrodeposition, allowed to obtain a stable measurement potential directly from the electrolyte containing bromide. The investigation of platinum electrochemistry in the presence of bromide by cyclic voltammetry led to the development of chronoamperometric protocols for the stable, precise and reproducible measurement in this environment. Hydrogen peroxide was detected under reaction conditions showing linear behaviour up to 20 mM with high sensitivity of 55 μA cm−2 mM−1 and excellent stability by application of a diffusion limiting hydrogel layer to the electrode surface. This linear range surpasses most micro- and nanostructured platinum approaches. Oxygen and hydrogen were both measured at elevated pressures up to 70 bar and high dissolved concentrations up to 52 mM and 40 mM with measured sensitivities of 26 μA cm−2 mM−1 and 356 μA cm−2 mM−1, respectively. We have successfully shown the application of electrochemical sensors for online, in situ monitoring of analyte concentrations under conditions found in direct synthesis microreactors.

Degradation kinetics and disinfection by-product formation of chlorimuron-ethyl during aqueous chlorination

Abstract The degradation kinetics of chlorimuron-ethyl during chlorination was analyzed, and the effects of the influencing factors of pH, bromide and ammonium concentrations and reaction temperature on degradation kinetics were evaluated. Regarding degradation kinetics, the chlorination of chlorimuron-ethyl followed second-order kinetics, first-order kinetics when the chlorine concentration was changed, and first-order kinetics when the chlorimuron-ethyl concentration was changed. The apparent second-order rate constant was calculated, which significantly decreased increasing pH. The rate constant of the reaction between chlorimuron-ethyl− and HOCl was calculated as 3.25 (±1.14) × 103 M−1 min−1, and under the acid-catalyzed condition, the rate constant significantly increased to 6.41 (±1.62) × 107 M−1 min−1. The degradation rate of chlorimuron-ethyl decreased with increasing bromide (at pH 5.5–7.0) and ammonium concentrations (≤6 μM). Chlorimuron-ethyl chlorination is an endothermic reaction, with an activation energy estimated as 22.46 kJ mol−1 using the Arrhenius equation. During chlorimuron-ethyl chlorination, chloroform was the major volatile degradation product during chlorimuron-ethyl chlorination, and its concentration increased with the increasing reaction time and pH level. The distribution of disinfection by-products (DBPs) formed at different solution pH levels was quite distinct. In the presence of bromide, the concentration and species of brominated DBPs increased with the increasing bromide concentration. Notably, carcinogenicity and mutagenicity of brominated DBPs were higher than their chlorinate analogs.

Controlling bromate formation in the Co(II)/peroxymonosulfate process by ammonia, chlorine-ammonia and ammonia-chlorine pretreatment strategies

The Co(II)/peroxymonosulfate (Co(II)/PMS) process, producing sulfate radicals (SO4•-), effectively removes organic pollutants in water, while producing a significant amount of bromate (BrO3−) in the presence of bromide (Br−). This paper investigates the ammonia (NH3) addition, chlorine-ammonia (Cl2-NH3) and ammonia-chlorine (NH3-Cl2) pretreatment strategies in controlling BrO3− formation in 20 min in the Co(II)/PMS process at pH 4.0. The addition of NH3 retarded the BrO3− formation, but only at a reduction level of about 9.5% for NH3 concentration of 50 μM, and was mainly attributed to the protonation of NH3 at pH 4 (99.99% as NH4+, did not react with HOBr). Both the Cl2-NH3 and NH3-Cl2 pretreatment strategies at HOCl and NH3 dosages of 15 and 50 μM, respectively, reduced 95% or more of the overall BrO3− formation and retarded the BrO3− formation, with the NH3-Cl2 pretreatment strategy outperforming Cl2-NH3. The reduction of the BrO3− formation was mainly attributed to the formation of monochloramine (NH2Cl) in both pretreatment strategies. NH2Cl effectively outcompetes SO4•- to react with HOBr and forms NHBrCl, with the apparent reaction rate constant between NH2Cl and HOBr more than 100 times faster than that between SO4•- and HOBr. However, the oxidation/degradation of NHBrCl in the Co(II)/PMS process reforms HOBr, and, although less in quantity, is oxidized to BrO3− at higher Co(II) and Br− concentrations. Thus, the NH3-Cl2 and Cl2-NH3 pretreatment strategies inhibit the BrO3− formation more significantly at lower Co(II) and Br− concentrations. In all cases, the generation of SO4•- in 20 min was not affected by the implementation of the three BrO3− pretreatment strategies.

Oxidation of steroid estrogens by peroxymonosulfate (PMS) and effect of bromide and chloride ions: Kinetics, products, and modeling

Recently, in situ chemical oxidation (ISCO) using peroxymonosulfate (PMS) for environmental decontamination has received increasing interest. In this study, oxidation kinetics and products of four steroid estrogens (i.e., estrone, 17β-estradiol, estriol, and 17α-ethinylestradiol) by PMS under various conditions were investigated. PMS could fairly degrade steroid estrogens over the pH range of 7–10, and the degradation rate increased with the increase of solution pH. This pH-dependence was well described by parallel reactions between individual acid-base species of steroid estrogens (E and E−) and PMS (HSO5− and SO52−), where specific second-order rate constants for E− with HSO5− and SO52− were in the range of 2.11–5.58 M−1s−1 and 0.77–1.25 M−1s−1, respectively. Identification of oxidation products by liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometer showed that PMS readily oxidized the phenolic group of steroid estrogens, leading to the generation of hydroxylated and ring-opening products. The presence of bromide and chloride ions (Br− and Cl−) at environmentally relevant levels could greatly accelerate the degradation of steroid estrogens by PMS with the formation of halogenated aromatic products. This effect was quantitatively estimated by a kinetic model, where the formation of free bromine and chorine and their rapid electrophilic substitution with steroid estrogens were taken into consideration. Eco-toxicity of transformation products of 17α-ethinylestradiol by PMS treatment in the absence and presence of bromide and chloride was estimated by quantitative structure–activity relationship analysis using ECOSAR. These findings advance the understanding of ISCO using PMS.

Palladium(II)-N-heterocyclic carbene-catalyzed direct C2- or C5-arylation of thiazoles with aryl bromides

Herein we report, a series of new benzimidazolium chlorides as N-heterocyclic carbene (NHC) ligand and their corresponding palladium(II)-NHC complexes with the general formula [PdCl2(NHC)2] were synthesized. All new compounds were characterized by 1H NMR, 13C NMR, IR spectroscopy and elemental analysis techniques. The catalytic activity of palladium(II)-NHC complexes was investigated in the direct C2- or C5-arylation of thiazoles with aryl bromides in presence of palladium(II)-NHC at 150 °C for 1 h. These complexes exhibited the good catalytic performance for the direct arylation of thiazoles. The arylation of thiazoles regioselectively produced C2- or C5-arylated thiazoles in moderate to high yields.

Formation of halogenated disinfection byproducts during the degradation of chlorophenols by peroxymonosulfate oxidation in the presence of bromide

Advanced oxidation processes based on sulfate radical (SO4−) have obtained great attention in water treatment and in-situ ground water/soil remediation. In this study, the degradation of chlorophenols (CPs) in Co2+ activated peroxymonosulfate (PMS) oxidation process was explored. It was found that 2-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol could be effectively removed in Co2+/PMS oxidation process. Presence of Br− greatly accelerated the transformation of the CPs, which can be explained by the formation of reactive bromine species including both bromine radical species and free bromine from the oxidation of Br− by SO4−. Br− could also be oxidized by PMS directly to form free bromine. Thus, degradation of the CPs was also observed in PMS oxidation process without any activators in the presence of Br−. Reactions between CPs and reactive bromine species resulted in the formation of brominated intermediates and disinfection byproducts (DBPs). Brominated phenolic intermediates such as Br2Cl-CP, BrCl2-CP, and Br2Cl2-CP were found in both Br−/PMS and Br−/Co2+/PMS systems. However, oxidized intermediates such as Br2Cl2-quinones were only identified in Br−/Co2+/PMS system. SO4− and radical bromine species are believed to be responsible for the formation of oxidized products. Bromoform and dibromoacetic acid were the main DBPs in both Br−/Co2+/PMS and Br−/PMS processes. Dichlorinated DBPs species, such as CHBrCl2 and dichloroacetic acid, were only found in Br−/Co2+/PMS system. Formation of dichlorinated DBPs suggests both dechlorination and chlorination reactions occurred, during which SO4− played a key role. The findings of this study indicate that presence of Br− can significantly facilitate the removal of organic contaminants but lead to brominated DBPs in PMS oxidation process, which should be taken into consideration when PMS is applied in environmental matrices containing Br−.

Dimethylglyoxime as an efficient ligand for copper-catalyzed hydroxylation of aryl halides

The CuI/dimethylglyoxime (CuI/DMG) catalyzed direct hydroxylation of aryl iodides with CsOH takes place at $$120{\,^{\circ }}\hbox {C}$$ in a mixed solvent system (DMSO– $$\hbox {H}_{2}\hbox {O}$$ ,1:1), afforded the corresponding phenols in good to excellent yield. Aryl bromides are found to be less reactive than aryl iodides under these reaction conditions. SYNOPSIS. (CuI/DMG) catalyzed synthesis of phenol from aryl iodide and aryl bromide in presence of mixed solvents ( $$\hbox {H}_{2}\hbox {O}$$ : DMSO) is reported in this paper. This protocol is general, economical, easy and convenient for transformation of aryl iodides and bromides to substituted phenols under mild reaction conditions.