Substituted Benzene Rings Research Articles

Degradation of enestroburin in the water-sediment system: kinetics, transformation products identification and toxicity assessment to aquatic organisms

ABSTRACT Pesticides inevitably enter the water environment in the process of use. However, the degradation and its transformation products (TPs) of enestroburin in water-sediment systems are not yet known. This study systematically investigated the degradation behaviour of enestroburin through indoor simulation experiments. The study demonstrated that the different organic content of sediments and oxygen conditions had a little effect on the degradation. The study also analysed transformation products by UPLC-QTOF-MS and MetabolitePilot software. A total of 3 TPs of enestroburin were identified, and one product (M-381) was confirmed and quantified. Based on these transformation products, the pathways of enestroburin were supposed, namely hydrolysis of chlorobenzene, hydrolysis of ester group and electrophilic substitution of benzene ring. Finally, ECOSAR software was utilised to predict the potential toxicity of the proposed TPs towards fish, daphnids, and green algae. The toxicity of TPs to aquatic organisms is lower than the parent compound, but they are still toxic. The study results provide data to support the safe use of enestroburin and provide a reference for the degradation and transformation of other strobilurin fungicides.

Strength and stability of π-π interaction between substituted benzene ring structures and graphene: Theoretical and molecular dynamics study

Adsorption between graphene and organic drug molecules attracts enormous attention for its wide application in drug delivery. π-π interaction, as one of the most important adsorption mechanisms, occurs between substituted benzene ring structure in organic drug molecule and graphene. This mechanism effectively prevents the degradation of molecular structure of drug, ensures its functional activity and promotes controlled release of drugs. It is worth noting that the type and quantity of substituents on the benzene ring have a significant impact on the strength and stability of π-π interactions. In this study, we cover features of eight kinds of substituents, and explore strength and stability of π-π interaction between graphene and substituted benzene ring structures from a mechanical perspective. The results demonstrate the advantages of substituents in enhancing adsorption strength. Electron-withdrawing substituents show more stronger enhancement effect than electron-donating substituents. Further research reveals that electrostatic interaction is the main enhancement mechanism for electron-withdrawing substituents. In addition, molecular dynamics simulations provide a comparison of adsorption stability among different substituents. Theoretical and simulation studies provide valuable mechanistic understanding of substituents in enhancing adsorption performance, contributing to the design and optimization of more targeting graphene carriers for drug molecules.

The Influence of Green Manure Planting on the Spectroscopic Characteristics of Dissolved Organic Matter in Freshwater-Leached Saline–Alkali Soil at Different Depths

This study investigated the influence of green manure planting on the spectroscopic properties of dissolved organic matter (DOM) in saline–alkali soil under freshwater leaching conditions at different soil depths. The UV254, UV253/UV203, α300, α355, SUVA254, SUVA260, and SR ultraviolet parameters indicated reductions in the content of large molecular substances, benzene ring substitution degree, colored dissolved organic matter, aromaticity, and hydrophobic components in the soil leachate DOM with an increasing soil depth. Compared with the non-green manure treatment control, green manure planting mitigated the leaching of dissolved organic matter in soil during saline irrigation, with rape green manure demonstrating superior effectiveness. Utilizing three-dimensional fluorescence combined with parallel factor analysis, this study analyzed three fluorescent components of soil leachate DOM: C1 (visible-light fulvic acid), C2 (humic acid), and C3 (tyrosine-like protein). The combined contribution of the two humic substance components (C1 + C2) was approximately 70%, indicating the dominance of humic substances in leachate DOM. The fluorescence parameters of soil leachate DOM included an average of the fluorescence index (FI) values between 1.4 and 1.9, low humification index (HIX) values consistently below 4, and biological index (BIX) values ranging from 0.8 to 1.0, suggesting a mixed source, low humification degree, poor stability, and moderate self-source characteristics. Compared with the non-green manure treatment control, both the green manure treatments exhibited a relatively higher proportion of biogenic sources and humification degree in soil leachate DOM. This suggests that planting green manure can reduce the relative DOM content under freshwater leaching conditions, increase the proportion of biogenic sources in soil leachate DOM, and enhance soil humification. Planting rapeseed green manure can diminish the leaching of DOM from land sources and augment soil humification.

Efficient removal of Basic Violet 16 by a multistage oxygen enhanced liquid glow discharge plasma system: Mechanism and roles of reactive species quantified by machine learning

A multistage oxygen enhanced Liquid Glow Discharge Plasma reactor (LGDP/multistage oxygen, LGDP/M-O2) was designed to improve the removal efficiency of organic dyes in wastewater. As a result of the multistage oxygen system, the degradation rate constant of Basic Violet 16 (BV16) was enhanced by approximately 18 times, the decolorization rate of BV16 was 97.39 % in 4 min, and the removal rate of TOC was 33.32 % in 10 min. Detailed study of how the system works to help break down pollutants. The reactive species series of experiments showed that multistage oxygen injection strongly promoted reactive species production and utilization. Meanwhile, a machine learning model to quantify the contribution of reactants was proposed. Machine learning indicated the dominating contribution of reactive oxygen species (63.89 %) and reactive chlorine species (21.92 %) in the degradation of BV16. In addition, the transformation intermediates during the degradation of BV16 were monitored. Accordingly, three possible degradation pathways of BV16 in the LGDP/M-O2 system were proposed, i.e., benzene ring substitution of hydroxyl groups, hydroxyl addition of C=C double bond, and halogenation of benzene rings. This study demonstrates the importance of the LGDP/M-O2 system for organic dye removal from wastewater.

Interesting Nuclear Magnetic Resonance studies of some N, N-bis(2-methoxyethyl) substituted Benzamides

DEET (N, N Diethyl m-toluamide) and DEPA (Diethyl phenyl acetamide) are synthetic compounds and proven potent insecticide and repellent respectively. In the search of effective mosquito repellent, different derivatives of DEPA or substituted benzamides were synthesized and their NMR analysis was carried out at low temperature. Sterically Crowded Bis (2-methoxyethyl) substituted Benzamides possess low rotational barrier and are floppy at room temperature. Alkyl arms attached to nitrogen become magnetically nonequivalent even at low temperature. Di ortho Substitution in benzamides enhanced hindered internal rotation and resulted splitting in methylene proton signals. The effect of substitution in benzene ring, on the splitting of methylene proton NMR is very well explained and the complete NMR data of substituted benzamides is described in this study for reference purpose.

The Effect of Temperature on Molecular Structure of Medium-Rank Coal via Fourier Transform Infrared Spectroscopy.

Fourier transform infrared spectroscopy (FTIR) was used to study the molecular structure of four medium- and low-temperature heat-treated medium-rank coals. The FTIR spectral parameters, which consist of CH2/CH3, aromaticity (fa), aromatic carbon rate (fC), aromatic hydrogen rate (fH), oxygen-containing (C-O) rate (IR), organic matter maturity (M), and the degree of aromatic condensation (Dc), indicate different characteristics, including changes in the aromatic hydrocarbon structure, fatty hydrocarbon structure, hydroxyl structure, and oxygen-containing functional groups of medium-rank coal. The results show that with the increase in heat treatment temperature, the sulfur content in coal gradually decreases, but the C/H ratio gradually increases. Meanwhile, the content of kaolinite and pyrite in coal gradually decreases, whereas the content of dolomite and hematite gradually increases. With the increase in heat treatment temperature, the relative content of ether oxygen hydroxyl groups in the hydroxyl structure significantly decreases, but the relative content of self-associated hydroxyl groups increases. The relative content of alkyl ether (C-O) in oxygen-containing functional groups gradually increases, whereas the relative content of aromatic nucleus C=C vibration presents a trend of first increasing and then decreasing. In addition, -CH2- is the majority in the structure of fatty hydrocarbons, and the absorption peak intensity of asymmetric -CH3 stretching vibration increases with the increase in heat-treated temperature. The structure of aromatic hydrocarbons mainly consists of four substituted benzene rings (except for R-303.15 K), in which the relative content of the trisubstituted benzene ring decreases with the increase in heat treatment temperature. With the increase in the heat-treated temperature of medium-rank coal, Dc, fH, fC, and fa show a trend of first increasing and then decreasing, M and IR reveal a trend of first decreasing and then increasing, and CH2/CH3 present a gradually decreasing trend. In conclusion, during the increase in the heat treatment temperature of medium-rank coal, the length of the fatty side chains in the fatty hydrocarbon structure becomes shorter, the number of branch chains continuously increases, and the maturity and condensation degree of organic matter first increases and then decreases. On this basis, further research on the effect of coal gasification suggests combining various technologies such as 13C NMR, XRD, and TG-MS to obtain semi-quantitative structural information of molecules in coal from different perspectives.

In-situ pyrolysis kinetic analysis and fixed-bed pyrolysis behavior of ex-service wind turbine blades

After the peak of rapid wind power development, a large amount of wind turbine blades reach/exceed their service life due to aging or damage. These ex-service wind turbine blades (EWTB) will increase the issue of its high-efficient utilization in the future decades. Among several treatment methods, pyrolysis has been considered as a promising solution to separate inorganic fiberglass and make organic epoxy resin (OER) high-value-added converted. However, the pyrolysis mechanism, chemical composition, and fiberglass separation of EWTB have not been deeply studied. In this paper, the synthetic model compound of epoxy resin was firstly used to investigate the thermal weight loss and pyrolysis kinetics, the thermal weight loss temperature range of which was 300 ∼ 480 °C. The apparent activation energy was minimum when the conversion rate was 0.6, and the pyrolysis mechanism was determined by the Coats-Redfern method as a diffusion control. On this basis, a lab-scale fixed-bed was conducted to study fast-heating pyrolysis characteristics of EWTB. It could be analyzed that the chemicals in the pyrolytic liquid were a series of phenolics with methyl and vinyl substituted benzene rings (e.g., bisphenol A, p-isopropenyl phenol, and phenol). Bisphenol A presented a relatively high selectivity of 51.02%, which could be recycled as the main raw material for the synthesis of epoxy resins. Furthermore, clean fiberglass could be separated by combusting the residual carbon in pyrolytic solids. These results might be useful for achieving the separation and resource utilization of organic and inorganic components of EWTB.

Preparation of Amide-Containing Insecticidal Derivatives from the Renewable Natural Product β-Pinene

The preparation of bioactive derivatives from the renewable natural product pinene is a hot research topic in the deep processing and utilization of pinene. In this study, β-pinene was used to develop novel molecules as a promising new precursor of insecticide. A series of amide-containing derivatives of β-pinene were synthesized and characterized. The insecticidal activities of these derivatives against Mythimna separate and Semiaphis heraclei were tested. The structure characterization results showed that the characterization data of amide-containing derivatives were in full agreement with their proposed structures. The insecticidal activities evaluation results indicated that amide-containing derivatives exhibited weak insecticidal activity against Mythimna separate, but exhibited moderate to good insecticidal activity against Semiaphis heraclei. After testing for 72 h, the corrected mortality against Semiaphis heraclei of compounds 5c, 5e, 5f, 5 h, 5j, and 5 m was 100% at 1000 mg/L. The structure-activity relationship analysis results showed that the introduction of an amide group into the structure of derivatives improved their insecticidal activity against Semiaphis heraclei. Meanwhile, the amide-containing derivatives containing the F and NO2 substituted benzene ring might improve their insecticidal activity against Semiaphis heraclei. This study will be helpful for the high value-added utilization of the natural renewable resource β-pinene and the development of novel insecticides.

Me-Better Drug Design Based on Nevirapine and Mechanism of Molecular Interactions with Y188C Mutant HIV-1 Reverse Transcriptase.

In this paper, the Y188C mutant HIV-1 reverse transcriptase (Y188CM-RT) target protein was constructed by homology modeling, and new ligands based on nevirapine (NVP) skeleton were designed by means of fragment growth. The binding activity of new ligands to Y188CM-RT was evaluated by structural analysis, ADMET prediction, molecular docking, energy calculation and molecular dynamics. Results show that 10 new ligands had good absorbability, and their binding energies to Y188CM-RT were significantly higher than those of wild-type HIV-1 reverse transcriptase(wt). The binding mode explained that fragment growth contributed to larger ligands, leading to improved suitability at the docking pocket. In the way of fragment growth, the larger side chain with extensive contact at terminal is obviously better than substituted benzene ring. The enhancement of docking activity is mainly due to the new fragments such as alkyl chains and rings with amino groups at NVP terminal, resulting in a large increase in hydrophobic bonding and the new addition of hydrogen bonding or salt bonding. This study is expected to provide reference for the research on non-nucleoside reverse transcriptase inhibitors resistance and AIDS treatment.

Synthesis of Coprinol and Several Alcyopterosin Sesquiterpenes by Regioselective [2 + 2 + 2] Alkyne Cyclotrimerization.

Alkyne [2 + 2 + 2] cyclotrimerization is a strategically attractive but tactically challenging approach to the synthesis of highly substituted benzene rings. Here, a bimolecular regioselective cyclotrimerization is applied to the total synthesis of the natural product coprinol and several related alcyopterosins from the illudalane family of sesquiterpenes. The synthesis of coprinol from dimedone was completed in six steps and a 57% overall yield. Alternative functional group manipulations lead to alcyopterosins A, B, and O and two additional congeners, all within six steps.

Oxo-Carotenoids as Efficient Superoxide Radical Scavengers.

Oxo-carotenoids containing conjugated carbonyl groups in their chains were designed to be more efficient superoxide radical scavengers than natural carotenoids, β-carotene and canthaxanthin. A practical chain-extension method for polyene dials (e.g., crocetin dial) was also proposed based on Horner–Wadsworth–Emmons olefination. Double aldol condensation between polyene dials and acetophenones with ring substituents produced oxo-carotenoids with substituted benzene rings. The antioxidant activity of oxo-carotenoids was measured using DPPH (radical) and ABTS (cationic radical) scavenging assays and compared with the analysis with the superoxide (anionic radical) probe. An effective conjugation length by carbon–carbon double bonds is important to provide superior antioxidant activity for oxo-carotenoids, regardless of the type of radical probe used in the assay. Increasing electron density is favorable to strong antioxidant activity in DPPH, and the phenol group is favored in ABTS, whereas electron deficient oxo-carotenoids are very potent in the superoxide radical assay. All oxo-carotenoids exhibited 105~151% better superoxide radical scavenging activity compared to beta-carotene (100%), whereas 38~155% in DPPH and 16~96% in ABTS radical scavenging activities were observed.

Coq3p relevant residues for protein activity and stability.

Coenzyme Q (CoQ) is an essential molecule that consists of a highly substituted benzene ring attached to a polyprenyl tail anchored in the inner mitochondrial membrane. CoQ transfers electrons from NADH dehydrogenase and succinate dehydrogenase complexes toward ubiquinol-cytochrome c reductase, and that allows aerobic growth of cells. In Saccharomyces cerevisiae, the synthesis of CoQ depends on fourteen proteins Coq1p-Co11p, Yah1p, Arh1p, and Hfd1p. Some of these proteins are components of CoQ synthome. Using ab initio molecular modeling and site-directed mutagenesis, we identified the functional residues of the O-methyltransferase Coq3p, which depends on S-adenosylmethionine for catalysis and is necessary for two O-methylation steps required for CoQ maturation. Conserved residues as well as those that coevolved in the protein structure were found to have important roles in respiratory growth, CoQ biosynthesis, and also in the stability of CoQ synthome proteins. Finally, a multiple sequence alignment showed that S. cerevisiae Coq3p has a 45 amino acid residues insertion that is poorly conserved or absent in oleaginous yeast, cells that can store up to 20% of their dry weight as lipids. These results point to the Coq3p structural determinants of its biological and catalytic function and could contribute to the development of lipid-producing yeast for biotechnology.

Reactivity and Mechanistic Issues in the Photocyclization of Dihalostyryl‐Naphthalenes towards Halo‐[4]helicenes: A Transposition on a Mallory Theme

AbstractOne of the most straightforward strategies nowadays for the synthesis of carbo‐ and hetero‐helicenes is the oxidative photocyclization of stilbene derivatives under Mallory conditions. In this study, the reactivity of a series of 3,4‐dihalostyryl‐naphthalenes (Hal=Br, F and Cl) has been investigated using Mallory conditions towards the corresponding halogenated [4]helicene compounds. The difluoro precursor afforded the two isomeric 2,3‐ and 1,2‐difluoro‐[4]helicenes, resulting from the ring closure on the two possible positions of the substituted benzene ring, the dichloro compound led to the formation of a mixture of the two isomeric 2,3 and 1,2‐dichloro‐[4]helicenes together with the 2‐mono‐chloro derivative, while the dibromo precursor provided, unexpectedly, only 2,3‐dibromo‐[4]helicene and the 2‐mono‐bromo derivative. DFT calculations performed on the entire series of precursors, final helicenes and intermediate dihydrohelicenes, including the non‐halogenated congeners, reveal the highly energetically favorable formation of a second dihydrohelicene intermediate following a [1,9]‐hydrogen sigmatropic transposition. Whereas the existence of this transposed dihydrohelicene intermediate, more stable than the initially formed dihydrohelicene by 15–30 kcal/mol, was until now “hidden” in the non‐substituted series, it allows herein to explain its re‐aromatization through formal elimination of HX in order to provide the 2‐mono‐halogenated‐[4]helicene derivatives.

Ipso.

On a substituted benzene ring the position that bears the substituent is designated as the ipso position. This Perspective presents the history behind that designation.

Biodegradation of Brown 706 Dye by Bacterial Strain Pseudomonas aeruginosa

Dyes are the most challenging pollutants for the aquatic environment that are not only toxic, but also interfering photosynthesis as light penetration into deep water is changed. A number of methods are used for the water reclamation, however, among them biological methods are preferably used due to their compatibility with nature. In the present research, 15 different bacterial strains were used to decolorize Brown 706 dye. Among the bacterial strains, Pseudomonas aeruginosa showed maximum decolorization activity; hence in the subsequent experiments Pseudomonas aeruginosa was used. First the decolorization activities were carried out under different physicochemical conditions to obtain the optimum decolorization benefits of the selected microorganism. The optimum conditions established were 37°C, pH of 7 and operation cycle time 72 h. In the subsequent experiment all optimum conditions were combined in a single experiment where 73.91% of decolorization efficiency was achieved. For the evaluation of metabolites formed after decolorization/degradation the aliquots containing bacteria were homogenized, filtered and then subjected to extraction. The extracted metabolites were then subjected to the silica gel column isolation. UV–Vis, FTIR, and NMR techniques were used to elucidate structures of the metabolites. Out of the collected metabolites only P-xylene was identified, which has been formed by cleavage of azo linkage by azo reductase enzyme of bacteria following the deamination and methylation of nitro substituted benzene ring.

Construction of N-Heterocycles Fused with a Highly Substituted Benzene Ring by a Benzyne-Mediated Cyclization/Functionalization Cascade Reaction and Its Application to the Total Synthesis of Marine Natural Products.

This account summarizes the development of a benzyne-mediated cyclization/functionalization protocol for the versatile construction of highly substituted benzene derivatives fused with an N-heterocyclic ring such as indolines, indoles, and related nitrogen-containing heterocycles. The protocol comprises sequential reactions initiated by generating a benzyne species and subsequent cyclization via addition of magnesium amide to the benzyne, followed by trapping of the resultant magnesium compound in situ with various electrophiles. The substituent scope was expanded by conducting a transmetalation on a copper species to introduce alkyl, aryl, and alkenyl substituents. The utility of the sequential reaction was demonstrated in the synthesis of a carbazole natural product (heptaphylline), pyrrolo[4,3,2-de]quinoline alkaloids (batzellines), and pyrrolo[2,3-c]carbazole alkaloids (dictyodendrines).

Synthesis and crystal structure of 1-hy-droxy-8-methyl-9H-carbazole-2-carbaldehyde.

Two crystallographically independent mol-ecules are present in the asymmetric unit of the title compound, C14H11NO2, with virtually identical geometries. The carbazole units are planar. The hy-droxy group at position 1, carbaldehyde group at position 2, and methyl group at position 8 (with the exception of two H atoms) are coplanar with the attached benzene rings. The dihedral angle between the two benzene rings is 2.20 (9)° in mol-ecule A and 2.01 (9)° in mol-ecule B. The pyrrole ring makes dihedral angles of 0.82 (10) and 1.40 (10)° [0.84 (10) and 1.18 (10)° in mol-ecule B] with the (-CH3)-substituted and (-OH and -CHO) substituted benzene rings, respectively. The mol-ecular structure is stabilized by the intra-molecular O-H⋯O hydrogen bonds, while the crystal structure features N-H⋯O and C-H⋯O hydrogen bonds. A range of π-π contacts further stabilizes the crystal structure.

Design, synthesis, structure activity relationship and molecular docking studies of thiophene-2-carboxamide Schiff base derivatives of benzohydrazide as novel acetylcholinesterase and butyrylcholinesterase inhibitors

The novel hydrazone derivatives of thiophene-2-carboxamide based benzohydrazide were designed, synthesized, characterized and explored for their potential as cholinesterase inhibitors and as antioxidants by in vitro analysis. Methylanthralate (1) was derivitized to Methyl 2-(thiophene-2-carboxamido)benzoate (3) by reacting it with 2-thiophencarbonyl chloride. The compound 3 was further treated with hydrazine hydrate to get N-(2-(hydrazinecarbonyl)phenyl)thiophene-2-carboxamide (4). 4 was further reacted with various aldehydes to obtain the desired Schiff base derivatives (5–20) in good yield (>85%). All compounds (1–20) were characterized by using FTIR, NMR spectroscopies and Mass spectrometric analysis. The biological evaluation results clearly showed that most of the synthesized compounds (5–20) are effective dual inhibitors with varying% inhibition values against butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) enzymes. Remarkably, compound 13 was established as the most active inhibitor of both BChE (% inhibition = 90.16%) and AChE (% inhibition = 83.21%) amongst the series, relative to the standard Donepezil (% inhibition = 92.34% for BChE and 95.24% for AChE). Moreover, the derivatives 6 and 20 also exhibited good inhibition against AChE with% inhibition of 79.41 and 78.79, respectively and against BChE with%age inhibition of 88.98 and 82.93, respectively. While, compounds 10 and 20 were found to possess good antioxidant potential with% inhibition of 89.23% and 94.49%, respectively. Structure-activity relationship showed that para substitution of benzene ring with more electronegative groups enhanced the activities of compounds against the enzymes. Binding interactions of the ligands with the active site of the enzymes were explored by carrying out molecular docking studies.

Enrichment of polychlorinated biphenyls in river water by using magnetic adsorbents with high selectivity to nonplanar aromatic compounds and their analysis with gas chromatography–mass spectrometry

AbstractPreviously our group reported a magnetic adsorbent, magGO@bottlebrush, which has high selectivity to nonplanar aromatic compounds with two or more phenyl rings. In this work, the magGO@bottlebrush was used for pre‐concentration of seven frequently concerned polychlorinated biphenyls (PCB28, PCB52, PCB101, PCB118, PCB138, PCB153, and PCB180) from river water samples, considering PCBs are hydrophobic compounds with two substituted benzene rings and have nonplanar structure, and gas chromatography–mass spectrometry (GC–MS) was used for the quantification. Several parameters affecting the extraction efficiency of the seven PCBs were investigated, under the best concerned extraction conditions, the developed method had excellent linearity (R2 > 0.9951) within the range of 1–100 pg/ml, it also possessed low limits of detection (0.33–0.90 pg/ml, S/N = 3) for the PCBs. Then, the enrichment and detection methods were applied to determine PCBs in two local rivers. PCB101, PCB118, and PCB138 were detected in one river, and their concentrations were 1.31, 0.69, and 10.01 pg/ml, respectively. The spiked recoveries of the river water samples were 63.33–119.29%, and the relative SD values were less than 17.33%. These results show that the proposed method has great potential application for the analysis of PCBs in river water samples.

Halogen-Halogen Nonbonded Interactions.

Halogen–halogen nonbonded interactions were studied for methyl halides and phenyl halides using both B3LYP and MP2 along with 6-311+G* and aug-cc-pVTZ. With the methyl halides, the linear approach was found to lead to little stabilization, whereas the “90°” approach gave 1–2 kcal/mol. This modest stabilization was due to long-range electron correlation effects. The lowest-energy arrangement had the molecules side-by-side, with the major stabilization being derived from halogen–hydrogen interactions. The results for methyl bromide were quite similar. Chlorobenzene dimer with the 90° orientation gave a small stabilization energy, but the best arrangement had the two benzene rings oriented over each other. The meta orientation of the chlorines had a lower energy than ortho or para. The dimerization energy was larger than that for two benzene rings sitting directly above each other, suggesting that whereas Cl···Cl interaction is not very important, the effect of the halogen on the electron distribution does have an effect. This suggests that much of the crystallographic results for these compounds may not be due to halogen–halogen interactions but rather the interaction between the substituted benzene rings along with crystal forces.