Synthesis of biofuel via levulinic acid esterification over porous solid acid consisting of tungstophosphoric acid and reduced graphene oxide

Research on Chemical Intermediates - Reduced graphene oxide (rGO) was synthesized by chemical reduction of graphene oxide with hydrazine hydrate and used as supports to prepare a series of...     

苯酰亚胺结构对PET阻燃抗熔滴及抑烟的贡献

通过本体聚合方法合成了一系列侧链含苯酰亚胺结构的聚对苯二甲酸乙二酯(PET)共聚酯.研究发现,苯酰亚胺单元的引入不仅提高了共聚酯的玻璃化转变温度(T_g)和高温成炭性,并且大大降低了共聚酯高温下的热分解速率.随着苯酰亚胺含量的增加,共聚酯表现出更高的氧指数(LOI)值和更好的阻燃抗熔滴效果.锥形量热测试结果表明,苯酰亚胺结构的引入可以有效地降低共聚酯的峰值热释放速率(p-HRR)、峰值烟释放速率(p-RSR)和总烟释放量(TSR).通过对纯PET和共聚酯燃烧测试后残炭的结构和形貌分析,发现苯酰亚胺结构有助于共聚酯形成石墨化程度更高的致密炭层,这些炭层起到隔热隔氧和抑制有机可燃烟气挥发的作用,在不引入传统阻燃剂的情况下,赋予共聚酯很好的本征阻燃性及抑烟性.     

Determination of Polycyclic Aromatic Hydrocarbons in Mosses by Ultrasonic-Assisted Extraction and Gas Chromatography–Tandem Mass Spectrometry

A facile method for the determination of polycyclic aromatic hydrocarbons in mosses is reported using ultrasonic-assisted extraction and gas chromatography–tandem mass spectrometry. The efficiency of ultrasonic-assisted extraction and the reagents was optimized. Tandem mass spectrometry with selective reaction monitoring was used to enhance the selectivity to reduce matrix interferences and simplify the purification protocol. The detection limits were from 0.1 to 2.0?ng/mL. The linear calibration range was two orders of magnitude and the coefficients of linear correlation exceeded 0.9992 for all analytes. The relative standard deviations within 1 day and 3 days were less than 9.0%. Recoveries from 56.8 to 109.0% were obtained in fortified mosses. The rapid, low solvent gas chromatography–tandem mass spectrometry method was used to determine polycyclic aromatic hydrocarbons in mosses.     

Synthesis of functionalized 3-arylpyridazines via Pd-catalyzed decarboxylative cross-coupling of pyridazine-3-carboxylic acids

An efficient and general protocol for the decarboxylative cross-coupling of pyridazine-3-carboxylic acids with aryl-bromides has been described. This method provides a new avenue for the synthesis of 3-arylpyridazines via decarboxylative cross-coupling strategy by employing the dual-catalyst system of Pd(PPh₃)₄/Cu₂O in the presence of Li₂CO₃ at 160 °C in DMA.     

Synthesis of SMND-309, a derivate of salvianolic acid B

(E)-2-(6-((E)-2-carboxyvinyl)-2,3-dihydroxyphenyl)-3-(3,4-dihydroxyphenyl) acrylic acid, designated SMND-309, was synthesized starting from 2-hydroxy-3-methoxybenzaldehyde in 12 steps and with an overall yield of 44%. The synthetic key features were the conversion of aryl aldehyde into aryl acetic acid for one-carbon extended, the Perkin condensation, and the Heck coupling for construction of α,β-unsaturated ester.     

Convenient one-pot synthesis of thiobarbituro-quinoline derivatives via catalyst-free multicomponent reactions in water

A one-pot, three-component condensation reaction of 8-quinolinol, 2-thiobarbituric acid and isatins or aldehydes in water to give novel barbituroquinoline derivatives for the first time, is described. The reaction is free of catalysts and toxic solvents, operating under mild conditions and allows for ease of product isolation, making it more environmentally friendly and suitable for large-scale operations.     

Super-Hydrophobic,Stable, and Swelling Nanoporous Solid Strong Acid

Super-hydrophobic solid strong acid with superior thermal stability and unique swelling properties has been synthesized by sulfonation of nanoporous polydivinylbenzene (PDVB) with super-acid of trifluoromethanesulfonic acid (TFMSA). The resultant PDVB–HOSO₂CF₃ has a well developed system of nanopores, superhydrophobic surface character and strong acid sites, and could be used as a highly efficient solid acid for catalyzing production of biodiesel and fine chemicals via transesterification, esterification and acylation. In terms of activity PDVB–HOSO₂CF₃ is superior to various solid acids such as SBA-15-SO₃CF₃, Nafion, Amberlyst 15, SBA-15-Ar-SO₃H and H form USY. The preparation of PDVB–HOSO₂CF₃ offers the way to develop new kind of porous solid acid with strong acid strength and regulated wettability.     

Single layer graphitic carbon nitride-modified graphene composite as a fiber coating for solid-phase microextraction of polycyclic aromatic hydrocarbons

The authors describe a three-dimensional single layer graphitic carbon nitride-modified graphene composite (g-C₃N₄@G) deposited on a stainless steel wire by a sol-gel technique. The coated fiber was applied to direct immersion solid-phase microextraction of trace levels of polycyclic aromatic hydrocarbons (PAHs) from cosmetics samples prior to their determination by gas chromatography with mass spectrometry (GC-MS). Due to π stacking interaction and hydrophobic interaction between the g-C₃N₄@G coating and the analytes (naphthalene, acenaphthene, fluorene, phenanthrene, fluoranthene and pyrene), the fiber displays an excellent adsorption capability for the analytes. Under optimized conditions, the method has a wide linear range, low LODs (from 1.0 to 2.0 ng L⁻¹), good repeatability and high recoveries. It was successfully applied to the determination of PAHs in cosmetics. The g-C₃N₄@G fiber also exhibited good durability.

Schematic of a three-dimensional single layer graphitic carbon nitride-modified graphene composite (g-C₃N₄@G) that was coated onto a stainless steel wire for the direct-immersion solid phase microextraction of trace levels of polycyclic aromatic hydrocarbons prior to gas chromatography-mass spectrometric detection.

     

Determination of Protonation Constants of O-Phospho-<Emphasis Type="SmallCaps">l</Emphasis>-serine in Aqueous Solution: Potentiometry,Microcalorimetry, NMR Spectroscopy and Quantum Chemical Calculations

O-Phospho-l-serine is one of the naturally occurring phosphorylated amino acids, having important pharmacological activity and bioactivity. The protonation constants of O-phospho-l-serine were determined by means of potentiometric titrations at 25 °C and ionic strength of 0.5 mol·L^?1 (NaCl). The heat effects of the protonation reaction of the O-phospho-l-serine were measured by direct calorimetry. NMR spectroscopy has demonstrated that the first protonation site occurs at the nitrogen atom in the amino group, followed by one of the oxygen atoms in the phosphono group, and finally the carboxyl oxygen atom. This trend is in good agreement with the enthalpy of protonation and quantum chemical calculations. These data will help to predict the speciation of O-phospho-l-serine in physiological systems.     

Synthesis of a Novel Double Salt: Ammonium 3,4‐Diamino‐1,2,4‐triazolium Styphnate

Nitrogen‐rich double salt ammonium 3,4‐diamino‐1,2,4‐triazoliumstyphnate (NH₄ · DATr · TNR) ( 2 ) with good thermal stability was successfully synthesized by reacting 3,4‐diamino‐1,2,4‐triazolium chloride aqueous solution with styphnic acid methanol solution under the reaction medium of aqueous ammonia. The title double salt was characterized by elemental analysis (EA), Fourier transformation infrared spectrum (FT‐IR), and X‐ray single‐crystal diffraction. It crystallizes in the monoclinic crystal system with space group P2₁/n. Its density is 1.780 g · cm^–3. Compound 2 is thermal stable below 200 °C by the differential scanning calorimetry (DSC) test. The non‐isothermal kinetics parameters were calculated by the Kissinger's method and Ozawa‐Doyle's method, respectively. In addition, compound 2 showed low friction and impact sensitivities.