Acidic ionic liquid [NMP]H2PO4 as dual solvent-catalyst for synthesis of β-alkoxyketones by the oxa-Michael addition reactions

Acidic ionic liquid N-methyl-2-pyrrolidonium dihydrogen phosphate [NMP]H₂PO₄ was prepared and used as efficient catalyst and reaction medium to synthesize β-alkoxyketones by the oxa-Michael addition reactions for the first time. The effect of anions and cations, amount of ionic liquid on the reaction was investigated. Various alcohols and phenols proceeded smoothly and led to corresponding β-alkoxyketones with high yields under mild reaction conditions, O-selectivity addition of aminoethanols was also achieved in this paper. Compared with traditional imidazolium ionic liquids, [NMP]H₂PO₄ gave the better results. The ionic liquid was stable and could be reused at least five times with a slight loss of activity.     

One-pot synthesis of tri- and tetra-substituted imidazoles using sodium dihydrogen phosphate under solvent-free conditions

<正>Sodium dihydrogen phosphate(NaH_2PO_4) efficiently catalyzes the condensation reaction of benzil,aldehydes,amines and ammonium acetate in a four-component reaction under solvent-free conditions.The reaction proceeds rapidly and affords the corresponding tetra-substituted imidazoles in high yields.Also an efficient route was developed for the synthesis of tri-substituted imidazoles from condensation of benzil,aldehydes and ammonium acetate using NaH_2PO_4.     

Rapid Dihydrogen Cleavage by Persistent Nitroxide Radicals under Frustrated Lewis Pair Conditions

Persistent radicals undergo hydrogen atom abstraction reactions with a great variety of substrates, but not with dihydrogen. It has now been found that the TEMPO radical splits dihydrogen under mild conditions in the presence of the strong bulky B(C₆F₅)₃ boron Lewis acid. The reaction is thought to proceed by a typical frustrated Lewis pair mechanism with the TEMPO radical acting as the active Lewis base. The reaction was analyzed by DFT, which indicates that no significant spin density on the hydrogen atoms is accumulated along the H₂ splitting reaction path.     

三聚磷酸二氢铝吸附Cd~(2+)的动力学研究

采用动态吸附法研究三聚磷酸二氢铝吸附镉离子的动力学行为并进行吸附活化状态热力学参数分析。结果表明,当三聚磷酸二氢铝粒径小于150μm、搅拌器转速大于200r/min、Cd2+的初始浓度为500mg/L时,三聚磷酸二氢铝对镉离子的化学吸附符合二级反应动力学方程,吸附速率常数k与温度T之间的关系符合Arrhenius方程式,吸附的活化能为Ea=27.93kJ/mol,吸附的频率因子A=65.33L/mg·min,ln(k/T)与1/T之间的关系符合Eyring公式,其活化焓ΔH=25.44kJ/mol,活化熵ΔS=-218.54J/mol·K。     

NaYF_4:Yb~(3+),Er~(3+)上转换发光纳米晶在三元混合溶剂体系中的配体交换修饰及发光性质

选用2-胺乙基膦酸双官能团小分子作为配体交换剂,采用氯仿/乙醇/水三元混合溶剂体系下的配体交换修饰方法,解决了疏水纳米晶与亲水配体的有效接触反应问题,实现了上转换纳米晶的水溶性以及表面胺基功能化修饰.通过傅里叶变转换红外光谱和热重分析证实了表面配体分子的替换.透射电子显微镜和激光粒度分析结果显示,所得水溶性纳米晶具有粒径均一,水力直径小和分散稳定的特点.样品的发射光谱结果表明,配体交换过程对纳米晶的发光无明显影响,保持了良好的发光性能.通过荧光共聚焦成像技术实现了胺基修饰上转换发光纳米晶对HeLa细胞的光学成像,证实所得纳米晶适合于潜在的生物学应用.     

In situ preparation and surface modification of magnesium hydroxide nanoparticles

Hydrophobic magnesium hydroxide (Mg(OH)₂) nanoparticles were successfully synthesized via a one-step solution precipitation method with octadecyl dihydrogen phosphate (n-C₁₈H₃₇OPO₃H₂, ODP) as a surface modifier. The ODP was used to control the growth of crystal in the c direction (direction perpendicular to the layers) and to modify the surface property of the Mg(OH)₂ particles produced from the precipitation. Measurements of relative contact angle and active ratio indicated that Mg(OH)₂ samples were hydrophobic. The samples were characterized by using field emission scanning electron microscope (SEM), X-ray diffraction (XRD), infrared analysis (IR). The mechanism of influence of ODP on the surface property and morphology of Mg(OH)₂ was discussed. Furthermore, from the results of the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) tests, it was confirmed that small amount of magnesium alkyl phosphate on the surface of Mg(OH)₂ particles enhanced the thermal stability of the low density polyethylene(LDPE)/Mg(OH)₂.     

Microtopographical studies of prism faces of potassium dihydrogen phosphate crystals

Surface structures on prism faces of potassium dihydrogen phosphate crystals grown from aqueous solutions and also by gel method are described and illustrated. Density of growth centres increases as the supersaturation of the mother liquor is increased. Gel grown crystals predominantly show rectangular growth hillocks on their prism faces. In the needle shaped crystals further nucleation extends predominantly along theC axis than at right angles to it. Influence of misoriented guest microcrystals on the growth of the prism faces is described.     

Synthesis and crystal structure of the pyridinium acid nitrate [(PyH)2(NO3)][H2(NO3)3] containing a dihydrogen trinitrate anion

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Synthesis of polyamides from diols and diamines with liberation of H2

The amidation reaction based on catalytic coupling of alcohols with amines previously reported by us, using the pincer complexes 1 and 2 as catalysts, was applied to the generation of polyamides from nonactivated diols and diamines. A range of polymers was prepared, with M_n up to 26.9 kDa. Unlike the traditional syntheses of polyamides based on carboxylic acid derivatives, which require the use of toxic reagents and generate stoichiometric amounts of waste, this process generates only molecular hydrogen as byproduct. Both aromatic and aliphatic diols and diamines were used. Gel permeation chromatography measurements of the dimethylformamide‐soluble polymers and thermal studies of the polyamides were performed. Matrix assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) spectra are also reported. Thermogravimetric analyses studies indicate that the aromatic polyamides (with the exception of the pyridine‐based polyamide) are more thermally stable than the aliphatic ones. This general, environmentally benign method for the synthesis of polyamides is homogeneously catalyzed under neutral conditions by dearomatized ruthenium‐pincer complexes 1 and 2 and proceeds in 1,4‐dioxane under an inert atmosphere. Conditions for polyamidation in the absence of solvent are also reported, using the pincer complex 2 as catalyst. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Theoretical description of dihydrogen/hydride and trihydride molybdocene complexes: An insight from static and molecular dynamics simulations

In this study ab initio Car–Parrinello molecular dynamics simulations, extended transition state (ETS)‐natural orbitals for chemical valence (NOCV) and QTAIM bonding analyses, were performed to characterize the ansa‐bridged molybdocene complexes [(C₅H₄)₂XMe₂MoH₃]⁺ for X = C, Si, Ge, Sn, Pb, and nonbridged Cp₂MoH system. The results have shown that the [(C₅H₄)₂CMe₂MoH(H₂)]⁺ complex exhibits nonclassical dihydrogen/hydride (H₂/H) conformation (97.6% of time of simulation), contrary to trihydride (H₃) structure noted for nonbridged Cp₂MoH (86.9%) and ansa‐bridged [(C₅H₄)₂SnMe₂MoH₃]⁺ (84.8%), [(C₅H₄)₂PbMe₂MoH₃]⁺ (84.9%) systems. Further, [(C₅H₄)₂SiMe₂MoH₃]⁺ and [(C₅H₄)₂GeMe₂MoH₃]⁺ complexes, appeared to exist in both conformations (H₂/H—55.4%, H₃—44.6% for Si‐based system and H₂/H—36.2%, H₃—63.8 % for germanium congener). It has been proven that the “steric availability” of the metal center, measured by the changes in the Cp? Mo? Cp angle (α), determines the existence of a given conformation—namely, the smaller value of the angle (molybdenum is sterically more accessible) the larger preference for the formation of dihydrogen/hydride structure. ETS‐NOCV method allowed to conclude that increase in the Cp? Mo? Cp angle (from α ca. 120° to α ca. 150°) leads to the enhancement of donation from H₂ and back‐donation from Mo to the σ*(H? H), what consequently leads to breaking of the H? H bond and formation of the trihydride structure. Systematical increase in the charge depletion from the σ‐bonding orbital of H₂ can be related to the reduction of the energy gap between the major orbitals involved in this contribution, namely highest occupied molecular orbital (HOMO) of H₂ with lowest unoccupied molecular orbital (LUMO) of [MoHL]⁺; ΔE = 0.0868 a.u. [for L =(C₅H₄)₂C], ΔE = 0.0827a.u. [for L = (C₅H₄)₂Si] ΔE = 0.0638 a.u. [for L = Cp₂]. Further, the relatively low energetic barrier to hydrogen exchange (ΔE^# = 3.3 kcal/mol) for carbon‐bridged complex, [(C₅H₄)₂CMe₂MoH_c(H_aH_b)]⁺ → [(C₅H₄)₂ CMe₂MoH_a(H_bH_c)]⁺, is related to strengthening of the Mo–H bonds when going from the substrate to the transition state (TS). Notably higher barrier to hydrogen rotation (ΔE^# = 10.1 kcal/mol) in [(C₅H₄)₂CMe₂MoH(H₂)]⁺ is due to lowering in the electrostatic stabilization as well as weakening of the donation (H₂ → Mo charge transfer) and practically lack‐of back‐donation (Mo → H₂) in the rotated TS. © 2012 Wiley Periodicals, Inc.