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In order to investigate the primary factors influencing hot‐spot formation in emulsion explosives sensitized by hydrogen‐storage glass microballoons (GMBs), we conducted impact calculations on hydrogen‐storage GMBs. The calculations focused on tracking two main mechanisms: the brittle collapse of GMBs and the adiabatic compression of internal gas. Various parameters were considered, including loading pressures, initial porosities, gas types, and initial gas pressures. Our findings indicate that the contribution of brittle collapse to hot‐spot formation is negligible, while adiabatic compression emerges as the predominant intrinsic mechanism for hot‐spot ignition in GMB‐sensitized emulsion explosives. Moreover, we observed that the ignition time remains similar for low‐pressure nitrogen and high‐pressure hydrogen. The addition of hydrogen does not result in an increased number of hot‐spots; however, it elevates the energy of each individual hot‐spot, thereby enhancing power delivery. Optimal selection of GMB size is crucial for hot‐spot formation and hydrogen storage. GMBs that are excessively large are prone to shell breakage, while overly small GMBs have limited hydrogen storage capacity. GMBs within the size range of 20 μm to 100 μm are deemed more suitable for emulsion explosives. [ABSTRACT FROM AUTHOR]

Based on the size‐ and shape‐selective sorption, 13X molecular sieves were developed as solid‐phase extraction adsorbents to cleanup serum extract for the determination of polybrominated diphenyl ethers. The important parameters affecting the cleanup efficiency were investigated including the amount of sorbents, the type, and volume of solvents. Under the optimized conditions, the capacity for removing impurities was evaluated via gel permeation chromatography and gas chromatography with mass spectrometry. The results demonstrated that up to 99% of lipids in corn oil (13 mg) can be removed after cleanup, and endogenous compounds in serum can also be effectively eliminated. The cleanup efficiency is not only superior to hydrophile‐lipophile balance column, but also close to acid silica gel and multifunction impurity sorbents. Generally, the developed cleanup method exhibited higher recovery for polybrominated diphenyl ethers with more than four bromines, especially for nona‐ and deca‐brominated diphenyl ethers (99.1˗117.8%). The cleanup method can be coupled with gas chromatography and tandem mass spectrometry for polybrominated diphenyl ethers analysis in human serum. The method detection limits were 0.01˗0.27 ng/mL and average recovery was 50.9˗113.3%, except 2,3',4',6‐tetrabrominated, 2,3',4,4',6‐pentabrominated, and 2,3,3',4,4',5',6‐heptabrominated diphenyl ethers. 2,2',4,5'‐Tetrabrominated diphenyl ethers had the highest detection frequency (95%) in human serum, whereas decabrominated diphenyl ethers had the maximum mean concentration (0.50 ng/mL). [ABSTRACT FROM AUTHOR]

Titanium, reserved abundantly in the earth, is a kind of metal with high energy density. In this study, RDX‐based titanium powder composite explosive is advocated by adding titanium powder into the RDX explosive as a dual additive. There are several stages in the energy release of composite explosives, and the initial chemical energy used for the detonation velocity tends to decline with the growth of the content of titanium powder. In the experiments, the maximum energy density Eρ of composite explosives is obtained with 20 % titanium powder through underwater explosion experiments, and it is increased by 15.33 % at 0.8 m and 19.31 % at 1.2 m compared with the RDX explosive, respectively, where more power would be obtained in limited space. At the same time, the thermodynamic parameters and kinetic parameters of TG‐DSC curves of composite explosives are studied, and it is determined that titanium powder is an insensitive agent to endow the composite explosives with good thermal stability. What's more, the results of this study may also support the mechanics of the safety performance of high energy explosives. Thus, titanium powder can be used as a potential energetic additive that plays a dual role in improving detonation characteristics and thermal stability of RDX‐based composite explosive. [ABSTRACT FROM AUTHOR]

Human exposure to bisphenols has rarely been reported. The most important challenges in this regard are the sensitivity and accuracy of the analytical methods employed. Dansyl chloride derivatization prior to high‐performance liquid chromatography–tandem mass spectrometry has been prevalently employed to improve sensitivity. However, the dose effect of the derivatization reagent on the reaction products is not well understood, especially for reactants with two or more active groups. This study investigated the mass ratio of dansyl chloride to bisphenols and found the mass ratio played a vital role in changing the composition of derivatives; further, the optimal ratio for obtaining di‐substituted derivatives was confirmed. Under optimal conditions, solid‐phase extraction followed by dansyl chloride derivatization coupled with high‐performance liquid chromatography–tandem mass spectrometry was used to detect eight bisphenols in human serum samples. The method detection limits of the eight bisphenols were 0.025‒0.28 ng/mL, and the recoveries were 72.9‒121.7% by spiking bisphenols (2, 5, and 20 ng/mL) into bovine serum. The detection frequencies of bisphenol A and bisphenol F in 73 serum samples obtained from children from Guangzhou were 41.1% and 71.2%, respectively, while the detection frequencies of other bisphenols were below 20%. The concentrations of bisphenol A and bisphenol F were < 0.28‒8.0 ng/mL and < 0.028‒7.6 ng/mL, respectively. [ABSTRACT FROM AUTHOR]

A new type of emulsion explosive sensitized by hydrogen‐storage has been invented previously. To better understand the role of hydrogen in emulsion explosives, the detonation experiments with different gas storage were conducted. Several gases, such as helium, oxygen, and nitrogen, were taken into account. Brisance tests, detonation velocity tests, and underwater detonation experiments showed that the high‐pressure hydrogen can improve the power and energy of emulsion explosive. The adiabatic compression of different gases was calculated. The pressure and temperature of the gas in GMs were obtained. Hydrogen has better compression performance than the other gases. Combining experiments and theoretical calculations can obtain that, hydrogen plays an important role in hot spots formation rate and emulsion explosive energy, and nitrogen and oxygen have little contribution to the energy of emulsion explosive, while helium is difficult to store in GMs and has a negative influence on the performance of emulsion explosive. [ABSTRACT FROM AUTHOR]

Due to regulation of the use of bisphenol A, several analogs serving as bisphenol A replacements have drawn substantial attention for their adverse health effects. To investigate their occurrence in humans and identify possible pollution sources, it is necessary to develop a sensitive method for total bisphenols detection. Thus, a method based on enzymolysis and liquid‐liquid extraction followed by molecularly imprinted polymer solid‐phase extraction and pre‐column derivatization with high‐performance liquid chromatography and tandem mass spectrometry was proposed. The developed method exhibited superior selectivity and sensitivity. The matrix effect can be eliminated to a great extent. The method detection limits for eight bisphenols were 0.05∼0.19 ng/mL. Satisfactory recoveries (71∼119%) were obtained by spiking bovine serum at three levels (0.8, 8 and, 20 ng/mL). The method was successfully applied to determine total bisphenols in the serum samples of children. Bisphenol A, bisphenol F, bisphenol S, bisphenol B and bisphenol F were detected with concentrations from below the method detection limit to 1.65, 0.45, 0.79, 2.04 and 0.17 ng/mL, respectively. These results indicate that bisphenol A remains the major pollutant among the studied bisphenols in children, whereas threats from bisphenol A analogs should also be monitored. [ABSTRACT FROM AUTHOR]

The dummy molecularly imprinted polymers were prepared by Pickering emulsion polymerization. 4,4′-(1-Phenylethylidene) bisphenol was selected as the dummy template to avoid the leakage of the target bisphenols. The microsphere particles were characterized by scanning electron microscopy and nitrogen adsorption-desorption measurements, demonstrating that the regular-shaped and medium-sized particles (40-70 μm) were obtained with a specific surface area of 355.759 m2/g and a total pore volume of 0.561 cm3/g. The molecular imprinting properties of the particles were evaluated by static adsorption and chromatographic evaluation experiments. The association constant and maximum adsorption amount of bisphenol A were 0.115 mmol/L and 3.327 μmol/g using Scatchard analysis. The microsphere particles were then used as a solid-phase extraction sorbent for selective extraction of seven bisphenols. The method of dummy molecularly imprinted solid-phase extraction coupled with high-performance liquid chromatography and diode array detection was successfully established for the extraction and determination of seven bisphenols from environmental sediment samples with method detection limits of 0.6-1.1 ng/g. Good recoveries (75.5-105.2%) for sediment samples at two spiking levels (500 and 250 ng/g) and reproducibility (RSDs < 7.7%, n = 3) were obtained. [ABSTRACT FROM AUTHOR]

A Brønsted acid ( p-TsOH⋅H2O) promoted alkylation/cyclization cascade reaction of pyrroles with N, N-dimethylaminomethyleneglutaconic acid dinitrile was efficiently realized to afford functionalized cyclopenta[ b]pyrroles with excellent diastereoselectivity. Deamination of the corresponding ammonium salts of the cyclopenta[ b]pyrroles with methyl iodide led to dihydrocyclopenta[ c]pyrroles. The cascade reaction pathway was confirmed by isolation and transformation of the reaction intermediate, i.e., the 2-alkylated pyrrole. [ABSTRACT FROM AUTHOR]

This work reports the preparation of molecularly imprinted polymer particles for the selective extraction and determination of four benzophenones from aqueous media. The polymer was prepared by using 4-vinylpridine as functional monomer, ethylene glycol dimethacrylate as cross-linker, acetonitrile as porogenic solvent and 2,2',4,4'-tetrehydroxybenzophenone as template. Good specific adsorption capacity ( Qmax = 27.90 μmol/g) for 2,2',4,4'-tetrehydroxybenzophenone was obtained in the sorption experiment and good class selectivity for 2,2',4,4'-tetrehydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dehydroxy-4,4'-dimethoxybenzophenone was demonstrated by the chromatographic evaluation experiment. Factors affecting the extraction efficiency of the molecularly imprinted solid-phase extraction procedure were investigated systematically. An accurate and sensitive analytical method based on the molecularly imprinted solid-phase extraction coupled with high-performance liquid chromatography and diode array detection has been successfully developed for the simultaneous determination of four benzophenones from tap water and river water with method detection limits of 0.25-0.72 ng/mL. The recoveries of benzophenones for water samples at two spiking levels (500 and 5000 ng/mL for each benzophenone) were in the range of 86.9-103.3% with relative standard deviations ( n = 3) below 9.2%. [ABSTRACT FROM AUTHOR]

Efficient palladium-catalyzed cross-coupling reactions of the internal olefins α-cyanoketene dithioacetals with a variety of olefins were achieved in dioxane/HOAc/DMSO (9:3:1 v/ v/ v) under air atmosphere or by means of AgOAc as the terminal oxidant. Electron-deficient terminal olefins reacted to form the linear diene derivatives with air as the oxidant. Styrenes underwent the cross-coupling to give both the linear and branched dienes when using AgOAc as the oxidant. Unactivated cyclic and linear internal olefin substrates both reacted in the presence of a catalytic amount of benzoquinone in air to produce skipped dienes. The typical products were structurally confirmed by X-ray crystallography. [ABSTRACT FROM AUTHOR]

Brønsted acid-mediated annulation of internal olefins α-oxo ketene dithioacetals to pyrroles was efficiently achieved to afford cyclopenta[ b]pyrroles. A pair of Brønsted acids with acid strengths, that is, trifluoroacetic acid, and para-toluenesulfonic acid hydrate, were applied to promote the annulation reactions. The resultant products were readily oxidized to sulfones by meta-chloroperoxybenzoic acid. Subsequent treatment with 1,8-diazabicyclo[5.4.0]undec-7-ene gave desulfurized terminal olefins or [2+2] cycloaddition products from the desulfurized olefin intermediates. The present protocol provides facile access to structurally diverse cyclopenta[ b]pyrrole derivatives under mild conditions. [ABSTRACT FROM AUTHOR]

The Brønsted acid-mediated alkylation and alkenylation of indoles were efficiently achieved by means of 3-(dimethylamino)acrylonitrile. Regulating the acidity of the reaction medium with para-toluenesulfonic acid monohydrate ( p-TsOH⋅H2O) and/or acetic acid (HOAc) led to versatile formation of 3-alkylated and 3-alkenylated indole derivatives under mild conditions. The 3-alkylated indole products could be nearly quantitatively transformed to the corresponding separable ( E)- and ( Z)-3-alkenylated indoles. [ABSTRACT FROM AUTHOR]

The palladium-catalyzed oxidative Heck-type allylation of β,β-disubstituted enones, i.e., α-oxoketene dithioacetals, was efficiently realized with allyl carbonates, providing a concise route to highly functionalized dienes. The present synthetic methodology utilizes the substrate activation strategy to activate the CH bond of β,β-disubstituted enones by introduction of a 1,2-dithiolane functionality to make the enone substrate highly polarized and thus increase its reactivity, demonstrating rare examples for transition metal-catalyzed allylic substitution of ß,ß-disubstituted enones through a Heck-type allylation process. [ABSTRACT FROM AUTHOR]

The functionalization of internal olefins has been a challenging task in organic synthesis. Efficient CuII-catalyzed trifluoromethylation of internal olefins, that is, α-oxoketene dithioacetals, has been achieved by using Cu(OH)2 as a catalyst and TMSCF3 as a trifluoromethylating reagent. The push-pull effect from the polarized olefin substrates facilitates the internal olefinic CH trifluoromethylation. Cyclic and acyclic dithioalkyl α-oxoketene acetals were used as the substrates and various substituents were tolerated. The internal olefinic CH bond cleavage was not involved in the rate-determining step, and a mechanism that involves radicals is proposed based on a TEMPO-quenching experiment of the trifluoromethylation reaction. Further derivatization of the resultant CF3 olefins led to multifunctionalized tetrasubstituted CF3 olefins and trifluoromethylated N-heterocycles. [ABSTRACT FROM AUTHOR]

A novel nanocomposite based on ordered graphitized mesoporous carbon (GMC) and amino acid ionic liquids (AAIL) is obtained through controlled surface modification of GMC with hydrophilic AAILs (1-ethyl-3-methylimidazolium alanine, EMIM[Ala]), which is used as a platform for a tyrosinase biosensor to detect phenol. The GMC-AAIL nanocomposite possesses a better biocompatibility and improved aqueous-phase dispersion than hydrophobic GMC alone, owing to the introduction of hydrophilic and biocompatible AAILs. Comparative studies revealed that the catalytic activity of tyrosinase for phenol in phosphate buffer solution (PBS) containing EMIM[Ala] was about ten times higher than that in pure PBS. By entrapping tyrosinase molecules into the mesopores of GMC, making use of the synergy effect of GMC and AAIL (the 'interspace confinement effect', the anti-fouling ability, and the biocompatible microenvironment), the GMC-AAIL-based biosensors display superior analytical performance to GMC-based ones in terms of signal-to-noise ratio, stability, repeatability, and working life. After 21-day storage, the electrode retained more than 90% of its initial response, indicating that surface modification of GMC with hydrophilic and biocompatible AAILs could significantly prolong the life of tyrosinase in vitro. The GMC10-EMIM[Ala]-based biosensor demonstrates a linear response for phenol concentrations from 0.1 to 10 µmol L−1 with a low detection limit of 20 nmol L−1 and sensitivity of 1385 mA cm−2 M−1. The GMC-AAIL nanocomposite proves to be a promising platform for enzyme-based biosensors and biocatalysis. [ABSTRACT FROM AUTHOR]

A molecularly imprinted polymer (MIP) was prepared using monobutyl phthalate as template. The synthesis was optimized by using different porogens and functional monomers. The MIP was used as a selective sorbent in molecularly imprinted solid-phase extraction (MIP-SPE) for pre-concentration and determination of monobutyl phthalate (mBP) from the bottled water. The difference in recognition selectivity of the polymer columns was observed in HPLC system, and the effect of the mobile phase on the performance of MIP columns was also investigated. Control of the MIP-SPE process is seen as important in helping to facilitate the selective extraction of mBP from water samples. Thereafter, the choice of washing solvent, eluting solvent amount, pH of loading sample, flow rate of loading solution and the loading sample volume was presented. The optimized procedure was described as follows: 25 mL spiked aqueous solution was percolated through the MIP-SPE cartridge at the flow rate of 1.5 mL/min. After rinsing with acetonitrile/methanol mixture (1:1, v/v), the bound analyte was desorbed with 3 mL methanol. The developed MIP-SPE method was demonstrated to be applicable for the analysis of mBP in the bottled water. [ABSTRACT FROM AUTHOR]