Efficient oxidative deprotection of trimethylsilyl,tetrahydropyranyl and methoxymethyl ethers under solvent-free conditions

A mild, efficient and fast method for direct oxidation of trimethylsilyl, tetrahydropyranyl and methoxymethyl ethers to their corresponding carbonyl compounds using trinitratocerium（Ⅳ） bromate （TNCB） supported on NaHSO4.H2O under solvent-free conditions is reported.

Interfacial engineering through lead binding using crown ethers in perovskite solar cells

In the domain of perovskite solar cells(PSCs),the imperative to reconcile impressive photovoltaic performance with lead-related issue and environmental stability has driven innovative solutions.This study pioneers an approach that not only rectifies lead leakage but also places paramount importance on the attainment of rigorous interfacial passivation.Crown ethers,notably benzo-18-crown-6-ether(B18C6),were strategically integrated at the perovskite-hole transport material interface.Crown ethers exhibit a dual role:efficiently sequestering and immobilizing Pb^(2+)ions through host-guest complexation and simultaneously establishing a robust interfacial passivation layer.Selected crown ether candidates,guided by density functional theory(DFT)calculations,demonstrated proficiency in binding Pb2+ions and optimizing interfacial energetics.Photovoltaic devices incorporating these materials achieved exceptional power conversion efficiency(PCE),notably 21.7%for B18C6,underscoring their efficacy in lead binding and interfacial passivation.Analytical techniques,including time-of-flight secondary ion mass spectrometry(ToF-SIMS),ultraviolet photoelectron spectroscopy(UPS),time-resolved photoluminescence(TRPL),and transient absorption spectroscopy(TAS),unequivocally affirmed Pb^(2+)ion capture and suppression of non-radiative recombination.Notably,these PSCs maintained efficiency even after enduring 300 h of exposure to 85%relative humidity.This research underscores the transformative potential of crown ethers,simultaneously addressing lead binding and stringent interfacial passivation for sustainable PSCs poised to commercialize and advance renewable energy applications.

Mechanism of chain propagation for the synthesis of polyoxymethylene dimethyl ethers

Polyoxymethylene dimethyl ethers(PODE)were synthesized from the reaction of paraformaldehyde with dimethoxymethane(DMM)over different acid catalysts at different conditions.Products were found to follow the Schulz-Flory distribution law.The chain propagation proceeds through the insertion of an individual segment of CH2O one by one,while the simultaneous insertion of a few CH2O segments or their assembly is unlikely.Due to the restriction of this law,it is difficult to increase the selectivity to the desired products(e.g.,PODE3 4).

Chemical equilibrium controlled synthesis of polyoxymethylene dimethyl ethers over sulfated titania

The chemical equilibrium and reaction kinetic behavior in the synthesis of polyoxymethylene dimethyl ethers （DMMn） were investigated over sulfated titania in order to reveal the decisive factor controlling the reaction. The results showed that the molar ratio of adjacent DMMn products in equilibrium solution had the same value, which depended absolutely on the reaction temperature. Meanwhile, the reactions had the same DMMn products distributions under varied reaction conditions. The equilibrium constants of the related step-wise reactions for DMMn formation were equal, which were calculated based on the bulk compositions of the reaction solution. And thus, the selectivity to DMMn was mainly controlled by the chemical equilibrium, i.e., thermodynamic control. In brief, the present results provide some guidance for future synthesis of DMMn.

Ecotoxicological effects of mixed pollutants resulted from e-wastes recycling and bioaccumulation of polybrominated diphenyl ethers in Chinese loach(Misgurnus anguillicaudatus)

To understand potential ecotoxicological effects of electrical and electronic equipment waste （e-waste） recycling and polybrominated diphenyl ethers （PBDEs） bioaccumulation in loaches, a semi-field experiment using Chinese loach （Misgurnus anguiUicaudatus） as experimental fish was performed. Larval loaches were kept in net-cage for three months in an e-wastes recycling site and a reference site in Southeastern China. There was significant difference of the survival rate between the loaches from the e-wastes recycling site （27%, 19/70） and from reference site （70%, 49/70）. Histopathological responses were also found in all the livers examined in loaches from the e-wastes recycling site. These results showed that mixed pollutants resulted from e-wastes recycling led to ecotoxicological effects on loaches. The bioaccumulation of polybrominated diphenyl ethers （PBDEs）, the main pollutants in e-waste, in loaches was also studied, the mean concentration of total PBDEs in sediment was 6726.17 ng/g wet weight and in water samples was 4.08 ng/L （dissolved phase）. BDE 209 was the dominant congener in sediment and with relatively high concentration in water. Relatively low concentration of BDE 209 （less than 0.01% of total PBDEs） and high concentration of BDE47 （up to 39.34% of total PBDEs） were detected in loaches.

A Synthesis, Process Optimization, and Mechanism Investigation for the Formation of Polyoxymethylene Dimethyl Ethers

Polyoxymethylene dimethyl ethers(DMM_n) are promising diesel additives. The synthesis of DMM_n from methylal(DMM) and paraformaldehyde over the NKC-9 acidic ion-exchange resin catalyst was investigated. Many unrecyclable by-products such as methyl formate, dimethyl ether and formic acid were produced in the reaction. To increase the selectivity of the desired products DMM_(3-6) and reduce the amount of unrecyclable by-products, the effects of reaction temperature, time, pressure and the molar ratio of the raw materials were evaluated through a series of single factor experiments. Experiments revealed that trace amount of water could suppress the formation of unrecyclable by-products, and the optimum initial water content(less than 2 wt%) was investigated. In addition, the synthetic process needs to go through the polyoxymethylene hemiformals intermediate stage, and then the DMM_n were obtained when polyoxymethylene hemiformals reacted with methanol. Ultimately, a possible mechanism is proposed to describe the formation of DMM_n from polyoxymethylene hemiformals in detail, in which it is revealed that the formation of carbocation intermediates is important in the reaction processes.

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.

Suppressing Li Dendrites via Electrolyte Engineering by Crown Ethers for Lithium Metal Batteries

Electrolyte engineering is considered as an effective strategy to establish stable solid electrolyte interface(SEI),and thus to suppress the growth of lithium dendrites.In a recent study reported in Advanced Functional Materials by Ma group,discovered that strong coordination force could be founded between 15-Crown-5 ether(15-C-5) and Li+,which facilitates the crown ether(15-C-1) to participate in the solvation structure of Li+ in the electrolyte for the same purpose.Such a novel strategy might impact the design of highperformance and safe lithium metal batteries(LMB s).

Occurrence of polybrominated diphenyl ethers in fish and shellfish downstream from electronic-waste recycling plants

We measured 39 polybrominated diphenyl ethers （PBDEs） in the muscle tissue of three species of fish （Sciaenops ocellatus,Sparus macrocephalus,and Lateolabrax japonicus） and four species of shellfish （Tegillarca granosa,Cyclina sinensis,Sinonovacula constricta,and Ostrea cucullata） that were collected downstream of electronic-waste recycling plants in Taizhou,China.A total of 24 PBDE congeners （PBDE 24） in the samples were detected.The PBDE 24 （total PBDE） ranged from 545.4 to 1688.7 ng/kg ww （wet weight）.The mean PBDE 24 concentration was 1382.6 ng/kg ww in fish and 858.1 ng/kg ww in shellfish.The lower brominated congeners were detected at relatively high concentrations in all species.The penta-products,produced from e-waste,were found at relatively low levels.A principal component analysis suggested a significant correlation among di-,tri-,tetra-,and hepta-BDEs for the three species of fish.Similarly,we found a significant correlation between mono-and tri-BDEs in the shellfish.Our results suggested that the processes of PBDE metabolism and elimination were similar in both fish and shellfish.In addition,the primary source of PBDEs appeared to be from the debromination of high brominated PBDEs.

Determination of brominated diphenyl ethers in atmospheric particulate matter using selective pressurized liquid extraction and gas chromatography–mass spectrometry with a negative chemical ionization

This study describes the development and validation of a sensitive and reliable method for determination of polybrominated diphenyl ethers（PBDEs）in atmospheric particulate matter using selective pressurized liquid extraction（SPLE）and gas chromatography–mass spectrometry with a negative chemical ionization（GC-NCI-MS）.Extraction and clean-up were performed using PLE with 2 g florisil and 3 g silica placed in the extraction cells.Under optimal conditions,14 PBDEs were extracted at 70℃ using hexane/dichloromethane（50：50,v/v）as solvent.Validation of SPLE returned excellent recoveries for most analytes,with relative standard deviations mostly below20%.Method detection limits ranged from 0.13 to15.38 ng·mL^-1 for the GC-MS analyses.The method was successfully applied to atmospheric particulate matter of Beijing,where analytes were detected in the range of182.79 to 468.99 pg·m^-3.

Analysis of Air Voids Evolution in Cement Pastes Admixed with Non-ionic Cellulose Ethers

Four cellulose ethers（CEs） were compared for their effects on the pore structure of cement paste using mercury intrusion porosimetry. The experimental results show that the total pore volume and porosity of cement pastes containing the four cellulose ethers are significantly higher than that of the pure cement pastes and the total pore volume and porosity of cement pastes containing HEC（hydroxyethyl cellulose ether） or low viscosity cellulose ethers are low in four CEs. By changing the surface tension and viscosity of liquid phase and the strengthening of liquid film between air voids in cement pastes, CEs affect the formation, diameter evolution and upward movement of air voids and the pore structure of hardening cement paste. For the four CEs, the pore volume of cement pastes containing HEC or low viscosity cellulose ethers is higher with the diameter of 30-70 nm while lower with the diameter larger than 70 nm. CEs affect the pore structure of cement paste mainly through their effects on the evolvement of the small air voids into bigger ones when the pore diameter is below 70 nm and their effects on the entrainment and stabilization of air voids when the pore diameter is above 70 nm.

Prediction of Aqueous Solubility for 209 Polychlorinated Diphenyl Ethers from Molecular Structural Parameters by DFT Method

Optimized calculations of 209 polychlorinated diphenyl ethers （PCDEs） and diphenyl ethers were carried out at the B3LYP/6-31G^＊ level with the Gaussian 98 program. Based on the theoretical linear solvation energy relationship （TLSER） model, the obtained structural parameters were taken as theoretical descriptors to establish the novel QSPR model for predicting aqueous solubility （-lgSw） of PCDEs. The model obtained in this work contains two variables： mean molecular polarizability （a） and the most positive partial charge on a hydrogen atom （qH^＋）, of which RE = 0.9606 and SD = 0.32. And the results of cross-validation test also show that the model exhibits optimum stability and better predictive power. Moreover, the predictive power of the new model is better than that of MCIs method.

Predicting the Relative Retention Time (RRT) of Polybrominated Diphenyl Ethers (PBDEs)

Using the molecular electronegativity distance vector descriptors derived directly from the molecular topological structures, the relative retention time （RRT） of polybrominated diphenyl ethers （PBDEs） were predicted. A four-variable regression model （M30） with the correlation coefficient of 0.9816 and the root mean square errors of 0.061 was developed using a training set including 30 PBDEs. The correlation coefficient of 0.9841 and the root mean square errors of 0.054 between the values of RRT predicted by M30 and the RRT observed for 16 external PBDEs show a good predictive potential of M30. The descriptors included in the M30 represent four interactions between four pairs of atom types, i.e., atom -C= and -C=, -C= and 〉C=, 〉C= and 〉C=, -C= and -Br.

A Convenient and Efficient Procedure for Oxime Ethers

Acetophenone oxime and benzaldehyde oxime were converted to oxime ethers in the presence of alkyl halide or methyl sulfate and KOH in aqueous DMSO in 5 to 70 min. The yields of oxime ethers were 70 - 96%.

Controllable synthesis of polyoxymethylene dimethyl ethers by ionic liquids encapsulated in mesoporous SBA-16

The promising combustion and emission properties of polyoxymethylene dimethyl ethers(PODEn)are of significant interest.However,the synthesis of PODEn products with desired chain lengths is still a problem facing synthetic PODEn.Herein,a series of unique IL@SBA16Cx solid catalysts are prepared by encapsulation of ionic liquids(ILs)within the nanocage of SBA16 through a silylation method.The structure of the encapsulated catalyst was characterized by UVvis spectra,Fourier transform infrared(FTIR),N2 adsorptiondesorption isotherms,Powder Xray diffraction(XRD),Transmission electron microscopy(TEM)and Elemental analysis.The encapsulated catalysts show similar catalytic activity to the homogeneous counterparts and display higher selectivity to the targeted PODE35 products than their homogeneous counterparts in the synthesis of PODEn from methanol(MeOH)and trioxymethylene(TOM).The encapsulated catalysts exhibit a superior PODE35 selectivity and could be the promising catalysts for PODEn synthetic reaction.

Solubilities of CO2 in some glycol ethers under high pressure by experimental determination and correlation

The binary vapor–liquid equilibrium data of CO_2 in diethylene glycol(monomethyl,monoethyl,monobutyl,dimethyl,diethyl,dibutyl)ether were determined from 288.15 to 318.15 K at pressure up to 6 MPa based on the constant-volume method.It was found by contrast that the ether group in solvents can promote the CO_2 absorption,but the hydroxyl group will inhibit the CO_2 absorption.Furthermore,the solubilities of CO_2 showed an upward trend with the increasing molecular lengths of absorbents.The experimental data were also correlated with a modified Patel–Teja equation of state(PT EOS)combined with the traditional van der Waals one-fluid mixing rules and the results showed a satisfactory agreement between the model and the experimental data.

Concentrations of Polybrominated Diphenyl Ethers in Maternal Blood,Placental Size,and Risk for Fetal Growth Restriction:A Nested Case-control Study

Objective To explore the effects of prenatal exposure to polybrominated diphenyl ethers(PBDEs)on placental size and birth outcomes.Methods Based on the perspective Wenzhou Birth Cohort,this nested case-control study included 101 fetal growth restriction(FGR)and 101 healthy newborns.Maternal serum samples were collected during the third trimester and measured for PBDEs by gas chromatography tandem mass spectrometry.The basic information of mother-newborn pairs was collected from questionnaires,whereas the placental size and birth outcomes of newborns were obtained from hospital records.Results A total of 19 brominated diphenyle ether(BDE)congeners were detected in maternal serum samples.Higher concentrations of BDE-207,-208,-209,and∑19PBDEs were detected in FGR cases than in controls.Increased BDE-207,-208,-209,and∑19PBDEs levels in maternal serum were related to decreased placental length,breadth,surface area,birth weight,birth length,gestational age,and Quetelet index of newborns.After adjusting for confounders,BDE-207 and∑19PBDE concentrations in maternal serum were significantly associated with an increased risk of FGR.Conclusion A negative association was found between PBDE levels in maternal serum and placental size and birth outcomes.Prenatal PBDE exposure may be associated with elevated risk of the incidence of FGR birth.

New monoterpene phenyl ethers from Illicium micranthum

Seven new monoterpene phenyl ethers,namely micranthumnins A-G(1-7),were isolated from the stem bark of Illicium micranthum(Illiciaceae).Their structures were elucidated by comprehensive spectroscopic analyses including MS,IR,1D and 2D NMR.All compounds were evaluated for their anti-AChE activities.

PMA-SiO_2 catalyzed synthesis of β-keto enol ethers

An efficient conversion of β-diketones into corresponding β-keto enol ethers with catalytic amount of PMA-SiO2 has been achieved.

Influence of Cellulose Ethers on Hydration Products of Portland Cement

Cellulose ethers are widely used to mortar formulations,and it is significant to understand the interaction between cellulose ethers and cement pastes.FT-IR spectra,thermal analysis and SEM are used to investigate hydration products in the cement pastes modified by HEMC and HPMC in this article.The results show that the hydration products in modified cement pastes were finally identical with those in the unmodified cement paste,but the major hydration products,such as CH（calcium hydroxide）,ettringite and C-S-H,appeared later in the modified cement pastes than in the unmodified cement paste.The cellulose ethers decrease the outer products and increase inner products of C-S-H gels.Compared to unmodified cement pastes,no new products are found in the modified cement pastes in the present experiment.The HEMC and HPMC investigation shows almost the same influence on the hydration products of Portland cement.