Progress in Analytical Methods of Halogenated Disinfection By-Products

Ensuring the health and safety of drinking water is crucial for both nations and their citizens.Since the 20th century,the disinfection of drinking water,effectively controlling pathogens in water sources,has become one of the significant advances in public health.However,the disinfectants used in the process,such as chlorine and chlorine dioxide,react with natural organic matter in the water to produce disinfection by-products(DBPs).Most of these DBPs contain chlorine,and if the source water contains bromine or iodine,brominated or iodinated DBPs,collectively referred to as Halogenated disinfection byproducts(X-DBPs),are formed.Numerous studies have found that X-DBPs pose potential risks to human health and the environment,leading to widespread concern.Mass spectrometry has become an important means of discovering new types of X-DBPs.This paper focuses on the study of methods for analyzing X-DBPs in drinking water using mass spectrometry.

Determination of the Toxicities of 16 Halogenated Benzenes to Photobacterium Phosphoreum and 2D- and 3D-QSAR Studies

In this paper we take photobacterium phosphoreum （T3） as the experimental bacteria, and determine the half-inhibitory concentration （-1gEC50） against the photobacterium phosphoreum of 16 halogenated benzenes. Using B3LYP method of DFT in the Gaussian 03 program, we obtain the structural and thermodynamic descriptors of 16 halogenated benzenes by fully-optimized calculation at the 6-311G＊＊ level. Taking the structural and thermodynamic descriptors as theoretical descriptors, the 2D QSAR model （R2 = 0.983） was established, which can be utilized to predict -lgEC50 of halogenated benzene according to the corrected linear solvation energy theory based on the experimental data of-lgECs0. In addition, the relationship between the toxicity and 3D spatial structure of the compound is studied by comparing the molecular similarity index analysis （CoMSIA） of 3D-QSAR method. By cross validation, the correlation coefficient q2 of CoMSIA model is 0.687, and the conventional correlation coefficient R2 = 0.958. The model is stable and reliable with great predictive ability. The 3D-QSAR model shows that the toxicity of halogenated benzene compound is mainly affected by the characteristics of hydrophobie field of the substituted halogens.

A QSRR Study on the Relative Retention Time of Halogenated Methyl-phenyl Ethers

Halogenated methyl-phenyl ethers （anisoles） are ubiquitous organic compounds in the environment. In the present study, geometrical optimization and electrostatic potential calculations have been performed for 42 halogenated anisoles at the HF/6-31 G^＊ level. A number of statistically based parameters have been obtained. By multiple regression method, linear relationships between the gas-chromatographic relative retention time （RRT） and structural descriptors have been established for the training set of 32 halogenated anisoles. The result showed that the parameters derived from electrostatic potentials （ESPs） together with the molecular volume （Vmc） could be well used to express the quantitative structure-RRT relationships of halogenated anisoles. The best two-variable regression model gives a correlation coefficient of 0.980 and a standard deviation of 0.07, and the leave-one-out cross-validated correlation coefficient is 0.975. The goodness of the model has been further validated through exploring the predictive power for the testing set of 10 halogenated anisoles.

Prediction of Infinite Dilution Activity Coefficients of Halogenated Hydrocarbons in Water

Geometrical optimization and electrostatic potential calculations have been performed for a series of halogenated hydrocarbons at the HF/Gen-6d level. A number of electrostatic potentials and the statistically based structural descriptors derived from these electrostatic potentials have been obtained. Multiple linear regression analysis and artificial neural network are employed simultaneously in this paper. The result shows that the parameters derived from electrostatic 2 potentials σtot^2, V s and ∑ Vs^＋, together with the molecular volume （Vine） can be used to express the quantitative structure-infinite dilution activity coefficients （γ^∞） relationship of halogenated hydrocarbons in water. The result also demonstrates that the model obtained by using BFGS quasiNewton neural network method has much better predictive capability than that from multiple linear regression. The goodness of the model has been validated through exploring the predictive power for the external test set. The model obtained via neural network may be applied to predict γ^∞ of other halogenated hydrocarbons not present in the data set.

Clicking ferrocene to halogenated boron-doped diamond surfaces

The halogenated boron-doped diamond （BDD） surfaces were reacted with sodium azide through a nucle- ophilic substitution reaction. The resulting azide-terminated BDD surfaces were used to trigger the ＂click＂ reaction. Because of the attractive electrochemical properties of ferrocene-containing molecules, such as fast electron transfer rates, reversible redox activities, and favorable redox potentials, we show that ferrocene derivatives can be grafted onto non-oxidized diamond surfaces by ＂click chemistry＂. These redox-active ferrocene-containing layers on a BDD surface, because of their ability to store and release charges reversibly, have the potential to be used as hybrid molecular/semiconductor memory devices.

Quantitative structure－activity study on the reductive dehalogenation potency of the halogenated aromatics

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Protecting-group-free amination of halogenated nitrobenzaldehyde with palladium catalyst

"One-step"method for the synthesis of secondary aliphatic amine substituted nitrobenzaldehyde was developed.In the presence of Pd catalyst,halogenated nitrobenzaldehyde could be smoothly coupled with secondary aliphatic amine to give the target product in hexamethylphosphamide(HMPT) media without the protection of aldehyde groups.

Ant Colony Optimization as a Powerful Tool for Descriptor Selection in QSPR Study of Infinite Dilution Activity Coefficients of Halogenated Hydrocarbons in Water

A quantitative structure-property relationship （QSPR） study was suggested for the prediction of infinite dilution activity coefficients of halogenated hydrocarbons, γ∞ , in water at 298.15 K. After optimization of 3D geometry of the halogenated hydrocarbons with semi-empirical quantum chemical calculations at the AM1 level, different descriptors （1514 descriptors） were calculated by the HyperChem and Dragon softwares. A major problem of QSPR is the high dimensionality of the descriptor space; therefore, descriptor selection is the most important step. In this paper, an ant colony optimization （ACO） algorithm was proposed to select the best descriptors. Then the selected descriptors were applied for model development using multiple linear regression. The average absolute relative deviation and correlation coefficient for the training set were obtained as 4.36% and 0.951, respectively, while the corresponding values for the test set were 5.96% and 0.929, respectively. The results showed that the applied procedure is suitable for the prediction of γ∞ of halogenated hydrocarbons in water.

QSRR Study on the Relationship between the Chromatographic Capacity Factor and Lipophilicity and Structure Parameters of Halogenated Thiophenols

The capacity factors （k＇） of fourteen types ofhalogenated thiophenols in different phases of methanol-water eluent were determined by reversed phased high-performance liquid chromatography （RP-HPLC） and the relationships between the logarithm of capacity factor lgK＇ and methanol ratio ψ were analyzed. A fair linear relationship is found between lgK＇ and ψ, and the correlation coefficients R2 of the constructed linear equations are all greater than 0.990. Relationship between the chromatographic data lgKw＇ when extrapolated to pure water and n-octanol/water partition coefficient lgKow obtained by the group contribution method has shown a good linear correlation with R2= 0.956. The structure parameters of fourteen halogenated thiophenols were calculated by using DFT, and the correlation equation of lgKw＇ and structure parameters was obtained by using SPSS, lgKw＇ = -0.409 ＋ 0.039a and R2 = 0.981, meaning that lgKw＇ is mainly determined by the polarizability α.

Halogenated thiophene substitutions on quinoxaline unit to achieve morphology optimization in efficient organic solar cells

Halogenated thiophenes are generally used units for constructing organic semiconductor materials for photovoltaic applications.Here,we introduced thiophene,2-bromothiophene,and 2-chlorothiophene units to the central core of quinoxaline-based acceptors and obtained three acceptors,Qx-H,Qx-Br,and Qx-Cl,respectively.Compared with Qx-H,Qx-Br and Qx-Cl showed enhanced absorption,down-shifted energy levels,improved crystallinity,and reduced energy disorder.The improved crystallinity significantly optimized the blend morphology,leading to efficient charge generation and transport and,therefore,less bimolecular recombination.Eventually,PM6:Qx-Br-based devices exhibited an outstanding power conversion efficiency of 17.42%with a high open-circuit voltage(VOC)of 0.915 V.Furthermore,Y6 was introduced into the PM6:Qx-Br binary system to improve the light utilization,and the resulting ternary devices delivered a high PCE of 18.36%.This study demonstrated the great potential of halogenated thiophene substitution in quinoxaline-based acceptors for building high-performance organic solar cell acceptor materials.

Electrophilic Halogen Reagents-mediated Halogenation: Synthesis of Halogenated Dihydro-1,3-oxazine Derivatives

Halogenation of N-cinnamylbenzamides and N-[(2H-chromen-3-yl)methyl]benzamides using electrophilic halogen source was reported.Various halogenated dihydro-1,3-oxazine derivatives(45 examples)were synthesized in high to excellent yields(up to 98%yields),as well as halogenated dihydrochromeno-1,3-oxazine derivatives(56 examples,up to 96%yields).The properties of mild conditions,metal-free and high efficiency of the reaction made it a promising strategy in future applications for the construction of carbon-halogen(fluorine,F;chlorine,Cl;bromine,Br;iodine,I)bond and 1,3-oxazine derivatives.

The promoting role of minor amount of water in solvent-free hydrogenation of halogenated nitrobenzenes

This study shows that minor amount of water plays a very important role in solvent-free hydrogenation of halogenated nitrobenzenes. For dried sponge Pd, the reaction cannot occur in the absence of water. For Pd/C catalyst, minor amount of water reduces the induction time, increases the reaction rate and reaction TOFs. Water might enhance the diffusion, adsorption and dissociation of H2 on Pd catalysts.

Chemistry,Biosynthesis,and Biological Activity of Halogenated Compounds Produced by Marine Microorganisms

Natural products derived from marine microorganisms have been received great attention as a potential source of new compound entities for drug discovery.The unique marine environment brings us a large group of halogen-containing natural products with abundant biological functionality and good drugability.Meanwhile,biosynthetically halogenated reactions are known as a significant strategy used to increase the pharmacological activities and pharmacokinetic properties of compounds.Given that a tremendous increase in the number of new halogenated compounds from marine microorganisms in the last five years,it is necessary to summarize these compounds with their diverse structures and promising bioactivities.In this review,we have summarized the chemistry,biosynthesis(related halogenases),and biological activity of a total of 316 naturally halogenated compounds from marine microorganisms covering the period of 2015 to May 2021.Those reviewed chlorinated and brominated compounds with the ratio of 9:1 were predominantly originated from 36 genera of fungi(62%)and 9 bacterial strains(38%)with cytotoxic,antibacterial,and enzyme inhibitory activities,structural types of which are polyketides(38%),alkaloids(27%),phenols(11%),and others.This review would provide a plenty variety of promising lead halogenated compounds for drug discovery and inspire the development of new pharmaceutical agents.

Room-temperature hydrogenation of halogenated nitrobenzenes over metal-organic-framework-derived ultra-dispersed Ni stabilized by N-doped carbon nanoneedles

Ultra-dispersed Ni nanoparticles(7.5 nm)on nitrogen-doped carbon nanoneedles(Ni@NCNs)were prepared by simple pyrolysis of Ni-based metal–organic-framework for selective hydrogenation of halogenated nitrobenzenes to corresponding anilines.Two different crystallization methods(stirring and static)were compared and the optimal pyrolysis temperature was explored.Ni@NCNs were systematically characterized by wide analytical techniques.In the hydrogenation of p-chloronitrobenzene,Ni@NCNs-600(pyrolyzed at 600°C)exhibited extraordinarily high performance with 77.9 h^(–1)catalytic productivity and>99%p-chloroaniline selectivity at full p-chloronitrobenzene conversion under mild conditions(90°C,1.5 MPa H2),showing obvious superiority compared with reported Ni-based catalysts.Notably,the reaction smoothly proceeded at room temperature with full conversion and>99%selectivity.Moreover,Ni@NCNs-600 afforded good tolerance to various nitroarenes substituted by sensitive groups(halogen,nitrile,keto,carboxylic,etc.),and could be easily recycled by magnetic separation and reused for 5 times without deactivation.The adsorption tests showed that the preferential adsorption of–NO2 on the catalyst can restrain the dehalogenation of p-chloronitrobenzene,thus achieving high p-chloroaniline selectivity.While the high activity can be attributed to high Ni dispersion,special morphology,and rich pore structure of the catalyst.

A review of halogenated natural products in Arctic,Subarctic and Nordic ecosystems

Halogenated natural products(HNPs)are organic compounds containing bromine,chlorine,iodine,and rarely fluorine.HNPs comprise many classes of compounds,ranging in complexity from halocarbons to higher molecular weight compounds,which often contain oxygen and/or nitrogen atoms in addition to halogens.Many HNPs are biosynthesized by marine bacteria,macroalgae,phytoplankton,tunicates,corals,worms,sponges and other invertebrates.This paper reviews HNPs in Arctic,Subarctic and Nordic ecosystems and is based on sections of Chapter 2.16 in the Arctic Monitoring and Assessment Program(AMAP)assessment Chemicals of Emerging Arctic Concern(AMAP,2017)which deal with the higher molecular weight HNPs.Material is updated and expanded to include more Nordic examples.Much of the chapter is devoted to“bromophenolic”HNPs,viz bromophenols(BPs)and transformation products bromoanisoles(BAs),hydroxylated and methoxylated bromodiphenyl ethers(OH-BDEs,MeO-BDEs)and polybrominated dibenzo-p-dioxins(PBDDs),since these HNPs are most frequently reported.Others discussed are 2,20-dimethoxy-3,30,5,50-tetrabromobiphenyl(2,20-dimethoxy-BB80),polyhalogenated 10-methyl-1,20-bipyrroles(PMBPs),polyhalogenated 1,10-dimethyl-2,20-bipyrroles(PDBPs),polyhalogenated N-methylpyrroles(PMPs),polyhalogenated N-methylindoles(PMIs),bromoheptyl-and bromooctyl pyrroles,(1R,2S,4R,5R,10E)-2-bromo-1-bromomethyl-1,4-dichloro-5-(20-chloroethenyl)-5-methylcyclohexane(mixed halogenated compound MHC-1),polybrominated hexahydroxanthene derivatives(PBHDs)and polyhalogenated carbazoles(PHCs).Aspects of HNPs covered are physicochemical properties,sources and production,transformation processes,concentrations and trends in the physical environment and biota(marine and freshwater).Toxic properties of some HNPs and a discussion of how climate change might affect HNPs production and distribution are also included.The review concludes with a summary of research needs to better understand the role of HNPs as“chemicals of emerging Arctic concern”.

Aliphatic Halogenated Hydrocarbons: Report and Analysis of Liver Injury in 60 Patients

Background and Aims:Intoxications by aliphatic halogenated hydrocarbons(AHH),used as effective solvents,are rare and may cause life-threatening liver injury.Patients with acute intoxications by AHH received an innovative treatment.Methods:Analyzed were data of 60 patients intoxicated by AHH,such as dichloromethane(n=3),chloroform(n=2),carbon tetrachloride(n=12),1,2-dichloroethane(n=18),1,1,2-trichloroethane(n=2),trichloroethylene(n=2),tetrachloroethylene(n=13)or mixed AHH chemicals(n=8),who received a new treatment consisting of CO2-induced hyperventilation to accelerate toxin removal via the lungs.Results:Added to the inspiration air at a flow rate of 2-3 Liter min-1,CO2 increased the respiratory volume up to 25-30 Liter min-1,ensuring forced AHH exhalation.This CO2-induced hyperventilation therapy was commonly well tolerated by the 60 patients and lasted for 106.0±10.5 hours.In most cases,initially increased liver test results of aminotransferases normalized quickly under the therapy,and liver histology obtained at completion of the therapy revealed,in the majority of patients,normal findings or fatty changes,and rarely severe single cell necrosis but no confluent liver cell necrosis.Despite therapy,clinical outcome was unfavorable for 4/60 patients(6.7%)of the study cohort,due to single or combined risk factors.These included late initiation of the CO2-induced hyperventilation therapy,intentional intoxication,uptake of high amounts of AHH,concomitant ingestion of overdosed drugs,consumption of high amounts of alcohol,and history of alcohol abuse.Conclusions:For intoxications by AHH,effective therapy approaches including forced hyperventilation to increase toxin removal via the lungs are available and require prompt initiation.

Environmental levels and toxicological potencies of a novel mixed halogenated carbazole

The present work involves an extensive analytical and toxicological description of a recently identified mixed halogenated carbazole found in sediment samples,1,8-dibromo-3,6-dichloro-9H-carbazole(BCCZ).Concentrations and the relative effect potency(REP)were calculated for the target BCCZ in a set of stream sediments collected in 2008 in Ontario,Canada.The levels calculated for BCCZ as compared to those previously assessed for legacy persistent organic pollutants(POPs)in the same samples revealed a significant contribution of BCCZ to the total organic chemical contamination(<1%e95%;average 37%).The corresponding dioxin toxic equivalencies(TEQs)of BCCZ in the sediment extracts were estimated from experimental REP data.The experimental data presented supports the classification of this emerging halogenated chemical as a contaminant of emerging environmental concern.Although potential emission sources could not be identified,this study highlights the importance of on-going research for complete characterization of halogenated carbazoles and related compounds.

Detection and Identification of a Novel Quinone Ketoxy Radical Produced by Metal-independent Decomposition of Hydroperoxides by Halogenated Quinones

We have shown recently that halogenated quinones could enhance the decomposition of hydroperoxides and formation of alkoxyl/hydroxyl radicals independent of transition

New preparation method for halogenated ethanes and methanes via base-catalyzed halogen dance

Although literature abounds with examples of formation of perhaloalkanes by photo-lytic or Lewis-acid induced halogen exchange reactions involving radical or carbocationintermediates,the procedures are seldom applicable to the preparation of perhaloalkanes ingood yields under mild conditions.Recently,we have reported the spontaneous reactionsof some perhalofluoroalkanes with various types of nucleophiles.All these reactions areinitiated by the halophilic attack of nucleophiles on C—Br or C—Cl bonds,followed byanionic chain steps involving carbanion as well as olefin intermediates.Notably,the latter areformed after the β-elimination of a good leaving group from the former.On the other hand,it is well known that halogenated carbanions can effectively make halophilic attacks on theC—X bonds of other halogenated substrates,e.g.,in the“halogen dance”of Bunnett.There-

Evaluation of N-acetylcysteine and glutathione as quenching agents for the analysis of halogenated disinfection by-products

Disinfection by-products(DBPs), formed from the reactions of disinfectants with natural organic matter and halides in drinking water, were considered to be cytotoxic and genotoxic, and might trigger various cancers. The relatively low concentration of DBPs in finished water(low μg/L or even ng/L levels) and the interference from water matrix inhibited in situ determination of DBPs. Moreover, the further formation and degradation of DBPs by disinfectants during the holding time(several hours to several days) from sample collection to analysis could adversely affect the determination of DBPs. To obtain accurate, precise and reliable data of DBP occurrence and formation, robust and reliable sample preservation is indispensable. However, the commonly used quenching agents(e.g., sodium sulfite, sodium thiosulfate, and ascorbic acid) for sample preservation can decompose reactive DBPs by reductive dehalogenation. This study evaluated the performance of N-acetylcysteine(NAC) and glutathione(GSH) as quenching agents for the analysis of halogenated DBPs by investigating the stoichiometry of the disinfectant-quenching agent reaction, the formation of DBPs during chlor(am)ination of NAC or GSH, and the effects of NAC or GSH on the stability of 18 individual DBPs and total organic halogen(TOX). Based on the results of this study, NAC and GSH were considered to be ideal quenching agents for the analysis of most DBPs and TOX, except halonitromethanes.