Ethyl Bromide Research Articles

Synthesis and Transformations of Novel Acetylene Glycols Derived from N-Substituted Piperidin-4-ones

With the aim to prepare asymmetric acetylenic γ-glycols, the reactions of 1-(2-ethoxyethyl)piperidin-4-one with propargyl alcohol were studied and the reaction conditions were optimized to reach satisfactory yields of the target glycols. Some transformations of the γ-glycols were studied. It was found that the reaction of 1-(2-ethoxyethyl)-4-(3-hydroxyprop-1-yn-1-yl)piperidin-4-ol with ethyl bromide involves exclusively the OH group on the quaternary carbon atom to form a monoethyl ether, and the mercury-catalyzed hydration involves cyclization with the elimination of a water molecule from the keto glycol moiety, leading to a spiroketone. It was shown that the catalytic reduction of 1-(2-ethoxyethyl)-4-[2-(1-hydroxycyclohexyl)ethynyl]piperidin-4-ol at atmospheric pressure produces a mixture of a saturated and an unsaturated products in a 1 : 2 ratio. Quantum-chemical calculations of the stable conformers of the synthesized asymmetric acetylenic γ-glycols were performed by the RHF/STO-3G method with geometry optimization using Gaussian 09 software.

Modification of halloysite clay nanotubes with various alkyl halides, and their characterization, blood compatibility, biocompatibility, and genotoxicity

Halloysite nanotubes (HNTs) clay were modified with alkyl halides, bromoethane (BrE), bromodecane (BrD), and bromooctadecane (BrOD), respectively. The FT-IR spectra of modified HNTs demonstrated an increase in the intensity of aliphatic –CH2 peaks at 2920 and 2850 cm−1 proportional to the number of C atoms in the modifying agent confirming the success of chemical modification with corresponding alkyl halides. Surface charge of NaOH treated HNTs, −65.7 ± 5.1 mV was increased to −37.1 ± 2.4, −40.6 ± 5.3, and −44.7 ± 1.9 mV, respectively upon chemical modification with BrE, BrD, and BrOD. The Surface area of the HNT clays, 43.2 ± 1.3 m2/g was also increased to 59.8 ± 2.7, 56.9 ± 2.1, and 47.9 ± 1.7 m2/g for BrE, BrD, and BrOD modified HNT clays, respectively. Base-activated HNT clays at 1 mg/mL concentration found to be nonhemolytic with 3.5 ± 1.2% hemolysis ratio, whereas HNT-BrOD clays were slightly exceeded hemolytic safety level with 6.6 ± 0.2% hemolysis induction. Base-activated HNT and HNT-BrOD clays were found to show antithrombogenic character with more than 100% blood clotting indexes,107.6 ± 1.8, and 106.5 ± 1.9%, respectively. Cytotoxicity studies of HNTs on L929 fibroblast cells revealed that HNTs in 12.5–200 μg/mL concentration range were shown dose-dependent cell viability, and above 50% cell viability was maintained at 200 μg/mL in all forms of HNT based clays administered.

Pesticide exposure and risk of cardiovascular disease: A systematic review

ABSTRACT The increase in pesticide consumption has a negative health impact. Studies point to an association between exposure to pesticides and cardiovascular disease (CVD), one of the leading causes of world mortality. This review synthesize evidence on the association between occupational exposure and environmental contamination by pesticides with CVDs from 1750 references databases (EBSCO, Medline, Science Direct, Scielo, Lilacs and Ovid) without date or language restriction. Selected 24 articles by PRISMA and Downs & Black methodologies, were included from inclusion criteria: original studies (case-control, cohort or cross-sectional design); clear CVD definition and exposure to pesticides; representative sample of the target population. The results show the occupational exposure to pesticides chlorpyrifos, coumafos, carbofuran, ethylene bromide, mancozeb, ziram, metalaxyl, pendimethalin and trifluralin was associated a risk of 1.8 to 3.2 for acute myocardial infarction. Primaphos, fenitrothion, malathion and deltamethrin pesticides were associated with a blood pressure increase. Environmental contamination by tetrachlorodibenzo-p-dioxin was associated with CVD with risk of 1.09 to 2.78 and organochlorine, 1.19 to 4.54; heavy metals, arsenic, trimethylarsine and dimethylarsinic acid with atherosclerosis and systemic arterial hypertension. These findings point to the association between exposure to pesticides and CVD, signaling the importance of greater rigor in the public policy related to pesticides.

Antimicrobial Activity of Hybrid Nanomaterials Based on Star and Linear Polymers of N,N'-Dimethylaminoethyl Methacrylate with In Situ Produced Silver Nanoparticles.

Well-defined linear and multi-arm star polymer structures were used as the templates for in situ synthesis and stabilization of silver nanoparticles (AgNPs). This approach led to hybrid nanomaterials with high stability and antibacterial activity to both Gram-positive and Gram-negative bacterial strains. The ecologically friendly so called “green” synthesis of nanomaterials was performed through AgNPs preparation in the aqueous solutions of star and linear poly(N,N′-dimethylaminoethyl methacrylate)s (PDMAEMAs); the process was followed with time. The size, shape, and zeta potential of the obtained hybrids were determined. To our knowledge, this is the first time that the antibacterial activity of PDMAEMA hybrid nanomaterial against Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa was investigated and assessed by minimum inhibitory concentration (MIC) and minimum biocidal concentration (MBC). Completely quaternized with ethyl bromide, star and linear PDMAEMAs were used in comparative biological tests. The modification of the polymers with in situ-formed AgNPs increased the antibacterial properties against all studied strains of bacteria by several times in comparison to non-modified polymers and quaternized polymers. These results yield novel nanohybrid materials that can be useful for applications in medicine and biology.

Wet corrosion of Al 1050 alloy in ethyl bromide-containing environment

The natural passivity, or induced by anodizing process, does not always result in an effective corrosion barrier for aluminium when exposed to environments containing specific chemicals that can cause material degradation phenomena with localized corrosion morphology. The present work investigates the effects of ethyl bromide (EtBr), a neutral organic molecule, sometimes used as a fumigant in packaging containers, that has been recently indicated as a possible cause of corrosion in aluminium alloy components. The study was conducted on Al 1050 alloy samples in aqueous solutions of sodium sulphate at increasing EtBr concentrations, ranging from 500 to 8600 ppm. Long-term exposure tests (936 h) and electrochemical experiments (potentiodynamic and potentiostatic polarizations, as well as time-dependent corrosion potential monitoring) were carried out, together with SEM and EDS examinations of the morphology and nature of the corrosion products. The results showed that the alloy undergoes different corrosion behaviours depending on the concentration of EtBr, spanning from passivity at the lowest concentrations to pitting at the highest, passing through the initiation and propagation of crevice at intermediate EtBr contents. A crucial role of the exposure time was detected, tentatively attributed to ethyl bromide hydrolysis in aqueous solution that liberates the bromide anion that is aggressive towards the passive state of aluminium alloys.

Poly(ε‐caprolactone) Single Crystals with Different Aspect Ratios Mediated by Counterion Exchange on the Basis of Hofmeister Series

AbstractAlthough polymeric single crystals fabricated from self‐assembly of block copolymers are reported, preparation of single crystals with different aspect ratios still remains a major challenge. In this work, a facile way is demonstrated to prepare poly(ε‐caprolactone) based single crystals with tunable aspect ratios through simple counterion exchange on the basis of the Hofmeister series. Briefly, after ion exchange from Brˉ (an ion‐containing triblock copolymer, poly(ethylene oxide)‐b‐poly(ε‐caprolactone)‐b‐poly(quaternized 2‐(dimethylamino)ethyl methacrylate)/ethyl bromide (PEO‐b‐PCL‐b‐qPDM‐Br)) to more hydrophobic anions, Iˉ, SCNˉ, PF6ˉ and OTfˉ, respectively, morphological transitions from spheres to wormlike micelles and sphere to 2D platelet structure with an increasing aspect ratio are observed. The morphological transition depends on the essential hydrophilicity of the qPDM‐X segment and increasing crystallinity of the PCL core caused by ion exchange. These findings provide a facile approach to the preparation of polymeric single crystals with tunable aspect ratios.

Ni-Catalyzed Enantioconvergent Coupling of Epoxides with Alkenylboronic Acids: Construction of Oxindoles Bearing Quaternary Carbons

We have developed a nickel- nickel/bisphosphine-catalyzed stereoconvergent cross-coupling reaction of epoxides with alkenylboronic acids. Racemic spiroepoxyoxindoles were converted to chiral homoal...

N-Alkylation Reaction in the Synthesis of Tetra-Substituted Glycoluryls

A new method is suggested herein for the synthesis of tetrasubstituted glycolurils by treatment of disubstituted glycolurils (di-tert-butylglycolurils, di-isopropylglycoluril) with alkylating agents such as methyl iodide, ethyl bromide and benzyl chloride in acetonitrile in the presence of KOH. Optimum conditions for the preparation of the target product in high yield were studied by the example of the synthesis of dibenzyl-di-tert-butylglycoluril: time 3 h and reaction temperature 75ºС at a 1:4 M/M molar ratio of disubstituted glycoluril to benzyl chloride. Thus, the target product yield was 83%. It was also found that benzyl chloride should be used as the alkylating agent because the product yield under the same equal conditions was higher with benzyl chloride than with benzyl bromide which in turn is more toxic and less available

Novel Synthesis of β-Keto Cycloacetals via Organoboranes

(Z)-1-Bromo-1-alkenylboronate esters were easily synthesized from the hydroboration of terminal alkynes with dibromoborane dimethyl complex under nitrogen atmosphere followed by treatment with propne-1,3-diol. These boronate esters are readily reacted with 1,3-dioxan-2-ylethyl)magnesium bromide in ether and tetrahydrofuran at -78 ºC for 1 h. The resulting "ate" complex upon addition of sodium methoxide in methanol undergo intramolecular nucleophilic substitution reactions to produce the corresponding (E)-alkenylboronate esters containing (1,3-dioxan-2-ylethyl) moiety in 70-82% isolated yields. The resulting intermediates are oxidized with sodium acetate and hydrogen peroxide to provide the corresponding β-keto cycloacetals in good yields (68-84%).

Dissociation characteristics of bromoethane under external electric fields

Bromoethane dissociates and generates the bromine radical under the radiation from the sun, which destroys the atmospheric ozone layer. So, it is necessary to take effective measures to degrade bromoethane. We use the density function theory (DFT) and calculate the dissociation properties and spectral characteristics of bromoethane under the external electric fields (0-0.028 5 a.u.) at the B3LYP/6-31G+(d, p) level. It is showed that the total energy of the molecule decreases as the external field increases from 0 a.u. to 0.028 5 a.u. along the Z-axis. Meanwhile, the energy gap decreases monotonically and the dipole moment increases. It is shown in the potential energy curves that the electric field of 0.030 a.u. is strong enough to break the C-Br bond. The results provide important information for the degradation of bromoethane under external electric fields.

Optimization and Validation of HS-SPME-GCMS Method for Determination of Multifumigant Residues in Grain, Oilseeds, Nuts, and Dry Fruit

Abstract Background: Fumigants are approved in many countries and used to treat food, feed, and seed. The amount of residue that remains in fumigated materials is measured and reported. Objective: The optimization and validation of a high-sensitivity headspace solid-phase microextraction gas chromatograph mass spectrometer (HS-SPME-GCMS) method for determination of eight fumigant residues—phosphine, methyl bromide, cyanogen, sulfuryl fluoride, ethylene oxide, propylene oxide, ethyl bromide and ethyl formate—in a range of food matrices were developed. The food matrices included grain, oilseed, dried fruit, and nut. Methods: The new method was used to determine residue levels from a fumigant complex in food matrices by monitoring the change of the absorption of spiked standards and desorption of fumigant from fumigated samples. Results: Based on the observation, the process of physical sorption and chemisorption was defined. The equilibrium time of the sample analysis was chosen at 5 hours. The LODs of the fumigants were in the range of 0.03 to 1.99 ng/g. Response to a range of diluted authentic standards gave significant linear regressions (r2 > 0.9983), and the RSDs were ≤8.7% at the 3 ng/g level of aged spiking standard, except for sulfuryl fluoride, for which the LOD was 1.99 ng/g and the RSD value was 39.7% (6.64 ng/g). Conclusions: The performance of the HS-SPME-GCMS method was more sensitive than the use of a gas syringe, except for sulfuryl fluoride. Highlights: An innovative multifumigant residue detection method based on HS-SPME sampling technology with gas chromatograph-mass selective detection (GC-MSD) analysis was established, including phosphine, methyl bromide, cyanogen, sulfuryl fluoride, ethylene oxide, propylene oxide, ethyl bromide, and ethyl formate; The first report of a sorption study of the process of physical sorption and chemisorption of residual fumigant in fruit and food matrices by an HS-SPME-GCMS method; Consider the effect of time on fumigant behavior in dried fruit, grain, and nut; The LODs of the fumigants were in the range of 0.03 to 1.99 ng/g.

Synthesis, Thermal Degradation and Dielectric Properties of Poly[octyl(triphenylethynyl)]silane Resin

Octyl(triphenylethynyl)silane monomer(OTPES) was synthesized with ethyl bromide, octyltrichlorosilane and phenylethylene by Grignard reaction. The molecular structure was confirmed by FTIR and NMR. The poly[octyl(triphenylethynyl)]silane resin(POTPES) was prepared by thermal polymerization and the corresponding thermal degradation behavior wasstudied by thermogravimetric analysis(TG) combining with model and model-free fitted methods. The dielectric property of resin was also studied by vector network analyzer. The results show that the melt point of OTPES was 50 °C and the processing window was over 236 °C. The resin degradation temperature of Td5 occurred over 433 °C and the char yield was over 60% at 800 °C. Based on Kissinger, Flynn-Wall-Ozawa, Coats-Redfern, Achar, Vyazovkin-Wight and Tang methods, the reaction activity(E) was 155.51, 152.97, 150.82, 146.02, 148.38 and 148.77 kJ/mol, respectively. Dielectric properties analysis displayed that the real part(e′) and the imaginary part(e″) of the relative complex permittivity of POTPES was 2.5 and 0.05, respectively, and the dielectric loss tangent was between 0.03 and 0.25. The reflection loss of resin was more than −2.85 dB in all range of 1–5 mm thicknesses and 2–18 GHz frequency, which indicated that POTPES resin was a real wave-transparent resin matrix.

Optimization and Validation of HS-SPME-GCMS Method for Determination of Multifumigant Residues in Grain, Oilseeds, Nuts, and Dry Fruit.

Background: Fumigants are approved in many countries and used to treat food, feed, and seed. The amount of residue that remains in fumigated materials is measured and reported. Objective: The optimization and validation of a high-sensitivity headspace solid-phase microextraction gas chromatograph mass spectrometer (HS-SPME-GCMS) method for determination of eight fumigant residues-phosphine, methyl bromide, cyanogen, sulfuryl fluoride, ethylene oxide, propylene oxide, ethyl bromide and ethyl formate-in a range of food matrices were developed. The food matrices included grain, oilseed, dried fruit, and nut. Methods: The new method was used to determine residue levels from a fumigant complex in food matrices by monitoring the change of the absorption of spiked standards and desorption of fumigant from fumigated samples. Results: Based on the observation, the process of physical sorption and chemisorption was defined. The equilibrium time of the sample analysis was chosen at 5 hours. The LODs of the fumigants were in the range of 0.03 to 1.99 ng/g. Response to a range of diluted authentic standards gave significant linear regressions (r² > 0.9983), and the RSDs were ≤8.7% at the 3 ng/g level of aged spiking standard, except for sulfuryl fluoride, for which the LOD was 1.99 ng/g and the RSD value was 39.7% (6.64 ng/g). Conclusions: The performance of the HS-SPME-GCMS method was more sensitive than the use of a gas syringe, except for sulfuryl fluoride. Highlights: An innovative multifumigant residue detection method based on HS-SPME sampling technology with gas chromatograph-mass selective detection (GC-MSD) analysis was established, including phosphine, methyl bromide, cyanogen, sulfuryl fluoride, ethylene oxide, propylene oxide, ethyl bromide, and ethyl formate; The first report of a sorption study of the process of physical sorption and chemisorption of residual fumigant in fruit and food matrices by an HS-SPME-GCMS method; Consider the effect of time on fumigant behavior in dried fruit, grain, and nut; The LODs of the fumigants were in the range of 0.03 to 1.99 ng/g.

Synthesis and antioxidant activity of some new thioglycoluril derivatives

ABSTRACTA series of S-alkylated products was prepared by alkylation of thioglycoluril with various alkylation agents, i.e. ethyl bromide, ethylene dibromide and chloroacetic acid. The synthesis performed in DMF at 60°C using sodium hydroxide as a base to give the corresponding products with significant advantages such as high conversions, short reaction time, mild reaction conditions, and low cost, simple workup with moderate to excellent yields. The structures of the synthesized compounds have been deduced from their spectral (IR, 1H-NMR and 13C-NMR) data. Significant antioxidant activity was observed for some members of the series.

S-Alkylated 1,2,4-Triazoles Derivatives Synthesis, spectral analysis and cytotoxicity evaluation

This paper presents synthesis, characterization and cytotoxicity assessment of six S-alkylated 1,2,4-triazoles derivatives that were obtained by treatment of some 1,2,4-triazole-3-thiones containing in the molecule phenylsulfonylphenyl and propyl or 4-bromophenylsulfonylphenyl and 4-methoxyphenyl fragments with different alkylation agents (ethyl bromide, ethyl chloroacetate or phenacyl bromide) in basic media. The synthesized compounds were physico-chemically characterized and the IR, 1H-NMR, 13C-NMR spectra were consistent with the assigned structures. The cytotoxicity of S-alkylated derivatives was evaluated on Daphnia magna crustacean.

Interplay of Solvation and Size Effects Induced by the Counterions in Ionic Block Copolymers on the Basis of Hofmeister Series

AbstractTwo ionic block copolymers with different lengths of hydrophilic segments, polystyrene‐b‐poly(quaternized 4‐vinylpyridine)/ethyl bromide, are prepared by sequential reactions. They are originally self‐assembled into so‐called “large compound micelles” in aqueous solution. After ion exchange of Iˉ, SCN,ˉ and PF6ˉ for Brˉ, morphological transitions are controlled by a competition of solvation and size effects of the newly introduced counterions. The solvation effect is dominated in a relatively short corona‐forming block. Thus, sphere‐to‐wormlike particles, sphere‐to‐vesicle, and sphere‐to‐precipitate transitions are observed. In contrast, due to a long corona‐forming block, size effects become more profound after adding SCNˉ, thereby no morphological transition occurs. A morphological transition is characterized after partial exchange of Iˉ for Brˉ for both diblocks. A sphere‐to‐wormlike particles transition is observed only after most Brˉ is replaced by Iˉ. This work extends the understanding of morphological regulation through simple ion exchange and encourages rational design of nano‐assemblies.

Effect of magnesium cluster size on Grignard reagent formation mechanism. A quantum-chemical study

The density functional theory (B3PW91/6-311[Formula: see text]G(2d,2p)) was used to obtain optimized geometry, energy and electronic properties of Mg[Formula: see text]EtBr adsorption complexes, Et[Formula: see text]Mg[Formula: see text]Br intermediates and transition states for ethyl bromide reaction with the magnesium atom and Mgn ([Formula: see text]–20) clusters modeling the distorted surface of the metallic magnesium. We suggest a consecutive multi-stage scheme of EtBr[Formula: see text]Mgn process in vacuum that includes adsorption of reagents on external cluster atoms, chemical interaction with Grignard reagent formation and desorption of products to the volume. Two fundamentally different reaction channels were investigated — the radical and molecular ones. Influence of Mgn cluster size on the preference of each of channels was established. It is shown that the reaction route is primarily determined with the position of the reactive group of atoms participating in formation of the transition state or radical intermediates and the activation energy of EtMgBr formation correlates with the energy of atom detachment from a cluster. For both pathways, reaction activation energies and thermodynamic parameters of the elementary steps were calculated.

A Validated GC-MS Method for the Determination of Genotoxic Impurities in Divalproex Sodium Drug Substance.

A specific GC-MS method has been developed, optimized and validated for the determination of five genotoxic impurities namely Methyl bromide (Me.-Br), Ethyl bromide (Et.-Br), Isopropyl bromide (Ipr.-Br), n-Propyl bromide (n-Pr.-Br) and n-Butyl bromide (n-But.-Br) in Divalproex sodium (DPS) drug substance. Chromatographic separation of five genotoxic impurities was achieved on DB-1 column (30 m × 0.32 mm, 3.0 μm), consists of 100% dimethyl polysiloxane as stationary phase and passing helium carrier gas. The mass fragments (m/z) were selected for the quantification of Me.-Br (m/z 94), Et.-Br (m/z 108), Ipr.-Br (m/z 122), n-Pr.-Br (m/z 122) and n-But.-Br (m/z 136). Bromide ion (m/z 79) was the qualifier ion for the analytes [(Me.-Br), (Et.-Br), (Ipr.-Br), (n-Pr.-Br) and (n-But.-Br)]. The performance of the method was assessed by evaluating the specificity, linearity, sensitivity, precision and accuracy experiments. The established limit of detection and limit of quantification values for the genotoxic impurities were in the range of 0.005-0.019 μg mL-1. The correlation coefficient values of the linearity experiment were in the range of 0.9947-0.9983. The average recoveries for the accuracy were in the range of 97.6-111.3%. The results proved that the method is suitable for the determination of Me.-Br, Et.-Br, Ipr.-Br, n-Pr.-Br and n-But.-Br contents in divalproex sodium.

How a Solvent Molecule Affects Competing Elimination and Substitution Dynamics. Insight into Mechanism Evolution with Increased Solvation.

Competiting SN2 substitution and E2 elimination reactions are of central importance in preparative organic synthesis. Here, we unravel how individual solvent molecules may affect underlying SN2/E2 atomistic dynamics, which remains largely unclear with respective to their effects on reactivity. Results are presented for a prototype microsolvated case of fluoride anion reacting with ethyl bromide. Reaction dynamics simulations reproduce experimental findings at near thermal energies and show that the E2 mechanism dominates over SN2 for solvent-free reaction. This is energetically quite unexpected and results from dynamical effects. Adding one solvating methanol molecule introduces strikingly distinct dynamical behaviors that largely promote the SN2 reaction, a feature which attributes to a differential solute-solvent interaction at the central barrier that more strongly stabilizes the transition state for substitution. Upon further solvation, this enhanced stabilization of the SN2 mechanism becomes more pronounced, concomitant with drastic suppression of the E2 route. This work highlights the interplay between energetics and dynamics in determining mechanistic selectivity and provides insight into the impact of solvent molecules on a general transition from elimination to substitution for chemical reactions proceeding from gas- to solution-phase environments.

Research Experience for the Organic Chemistry Laboratory: A Student-Centered Optimization of a Microwave-Enhanced Williamson Ether Synthesis and GC Analysis

An inquiry-based experiment for the organic chemistry laboratory was developed to provide students with a cognitively rich research experience. Student teams were charged with optimizing the reaction conditions for the Williamson ether synthesis of 2-fluorophenetole from 2-fluorophenol, ethyl bromide, and potassium carbonate in either absolute ethanol or acetonitrile. Microwave acceleration of this SN2 reaction followed by rapid GC–MS analysis allowed students to review results, revise experimental conditions, and repeat the modified reaction and its analysis within a 3 h laboratory period. Variables that could be manipulated were reagent equivalencies, solvents and their volume, microwave reaction time, temperature, and wattage. Post-laboratory, all team data were available to the entire class for additional evaluation and each student was required to suggest new conditions for improvement in his/her laboratory report.