Methyl transfer reactions are of great significance in the field of synthetic chemistry and life sciences.So far, most of the reported methyl migration reactions have occurred between different types of molecules.Therefore, it is of certain value to search for new methyl transfer reactions.In this study, fenthion, a most common insecticide in the environment, was selected as the studied object, and electrospray ionization mass spectrometry (ESI-MS) was used as the analytical tool to conduct highly sensitive analysis of the reaction system, so as to explore the possibility of methyl transfer reaction in fenthion molecules under the condition of trifluoroacetic acid and nanometer titanium dioxide.Other than m/z 279 (protonated fenthion), some new product ions (m/z 293 and m/z 265) could be observed in the fingerprint MS of fenthion reaction solution.Tandem MS experiments showed that the intensity of product ion m/z 231 (elimination of CH 3 SH) in the dissociation of m/z 279 from fenthion reaction solution were different from that from protonated fenthion standard.This indicated that the methyl in the fenthion could transfer from oxygen atom to unsaturated sulfur atom via 1,3-methyl transfer, forming isomer a2, which led to the high intensity of product ion m/z 231 in the dissociation of m/z 279 from fenthion reaction solution.Under the assistance of acid, the methyl cation continued to transfer from sulfur atom in a2 to the unsaturated sulfur atom in another fenthion molecule, forming a3 (m/z 293) and a4 via intermolecular methyl transfer reaction, which was verified by tandem MS experiments of ions at m/z 293 and m/z 265.In addition, density functional theory (DFT) calculations were carried out to confirm the mechanism of intramolecular and intermolecular methyl transfer reactions of fenthion.In order to observe the phenomenon of methyl transfer more intuitively, the effects of different acids, metal oxides, reaction time and reaction temperature on the signal intensities of ions at m/z 265 and m/z 293 of intermolecular methyl transfer reactions of fenthion were investigated.It could be concluded that under the conditions of trifluoroacetic acid and nanometer titanium dioxide, and 60 ℃ ultrasound reaction for 6 h, the proportion of intermolecular methyl transfer reactions of fenthion was the highest.In
Abstract A carboxylative coupling reaction of various primary amine and 3‐phenyl‐2‐propynyl or 2‐nonynyl chloride in the presence of 8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) using carbon dioxide as carboxylative reagent was presented. This transition‐metal free reaction system shows broad substrate scope and gives a series of propargylcarbamates in moderate to good yield. The obtained N ‐alkyl substituted carbamate product can undergo base‐catalyzed intramolecular cyclization reaction to afford functionalized 4‐methylene‐2‐oxazolidinone in good yield.
Microcrystalline graphite (MG) was used as raw material and oxidated by Hummers method. And further the graphene oxide (GO) was obtained by ultrasonic stripping. The TP modified graphene (TPG) was prepared by the surface grafting of pure natural green tea extract tea polyphenols (TP) on the surface of GO. Finally, the TPG/epoxy resin composite was prepared by solution blending and heat-curing moulding method.The characterization of structure and properties of TPG was analyzed by X ray diffraction pattern (XRD), infrared spectroscopy (FT-IR), thermo gravimetric analysis (TGA) and X ray photoelectron spectroscopy (XPS). A universal material testing machine was used to test the mechanical properties of epoxy resin composites with different addition of TPG. Field emission scanning electron microscopy (SEM) was used to observe the tensile-sectional morphology of the composites. The thermal stability of the composites was investigated by thermogravimetry and thermal dilatometer. The experimental results showed that the TP molecule was successfully grafted on the oxygen-containing functional groups of the GO surface through the phenolic hydroxyl group.When the addition of TPG was 1.0 wt%, the decomposition temperature of the epoxy resin was increased by 22.2 °C,and the surface resistivity decreased from 1.35×10 14 Ω·m to 1.7×10 9 Ω·m. When the added amount of TPG was 0.5 wt%, the tensile strength of composites was increased by 13.5% reaching 59.85 MPa.
Chiral iminopyridine oxazoline (IPO) ligands were designed, synthesized and utilized for the first cobalt-catalyzed highly regio- and enantioselective anti-Markovnikov hydroboration of 1,1-disubstituted aryl alkenes. These novel IPO ligands will likely be of high value for asymmetric transformations with first-row transition metals.
The new type of copper matrix self-lubricating composites were prepared by powder metallurgy route. The influences of milling way and content of molybdenum disulfide on composites’ microstructure and tribological properties were researched. It is found that, M o S 2 can’t participate in the process of mechanical alloying together with graphite and copper powder. When the mass fraction of M o S 2 increases from 0% to 10%, the coefficient of friction of composites M o S 2 -G-C u reduces correspondingly, however the three-dimensional network structure of copper matrix was damaged seriously in sample 10% M o S 2 -G-C u .After the wear text there will come out solid self-lubricating film on the surface of sample 5% M o S 2 -G-C u and 10% M o S 2 -G-C u .
Abstract A novel difunctionalization of unactivated alkenes has been reported via visible light‐promoted three‐component carboazidation using TMSN 3 and acrylonitrile as partners without any stoichiometric oxidants. This protocol is operationally simple for straightforward access to azido derivatives with good functional group tolerance from readily available starting materials. A facile azido radical‐catalyzed [3 + 2] cycloaddition reaction of vinylcyclopropane with acrylonitrile was also observed to deliver a multi‐substituted cyclopentane.
Fissure fillings are critical to the hydro-mechanical properties of jointed rock masses in rock engineering. In this study, triaxial seepage tests were performed on standard cylindrical fissure-filled sandstone. The characteristics of stress–strain relationships, absorption and consumption of energy, variations in deformation resistance, and permeability evolution during the experimental process, along with the crack development observed in post-failure computed tomography scan images of the sandstone specimens were analyzed. The results demonstrate that the fillings improve the energy capacity and reduce the damage accumulation of sandstone specimens, with sand-filled specimens performing better than mud-filled specimens, especially at lower bridge angles. The fillings can reduce the depth of crack extension and lessen the influence of prefabricated fissures on sandstone failure, with this effect diminishing as the rock bridge angle increases. Permeability decreases in the pre-peak failure stage as the fillings improve the deformation resistance of the sandstone specimens. In the post-peak failure stage, the fillings and rock debris generated by the sandstone failure move within the developed fractures, causing significant fluctuations in permeability. These findings deepen the understanding of the hydro-mechanical properties of jointed rocks and provide a scientific basis for stability analysis in rock engineering.
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