钴的羟胺酸类配合物催化对-二甲苯氧化反应研究

合成并表征了 3种羟胺酸类钴配合物 Co(OTPHA) 2 、Co(OTBHA) 2 和 Co(OTOHA) 2 ,并对比评价了它们催化对 -二甲苯均相液相氧化合成对 -甲基苯甲酸的活性和选择性 .考察了以纯氧为氧源 ,常压下反应温度、催化剂浓度、反应时间以及水对反应转化率和选择性的影响 .实验结果表明 ,不同分子结构的配体 ,可以通过其空间效应和电子效应对催化活性产生直接的影响 ,3种催化剂的活性顺序为 :Co(OTPHA) 2 >Co(OTBHA ) 2 >Co(OTOHA ) 2 .当反应温度为 110℃、催化剂浓度 1.0× 10 - 3mol/ L、反应 6 h时 ,催化剂 Co(OTPHA) 2 的对 -二甲苯转化率可达 33.9%、选择性为 86 .2 % .若提高反应温度和加大催化剂浓度 ,则会降低催化剂的活性 .反应中生成的水对氧化反应有抑制作用 ,应及时将反应中生成的水从体系中分出     

羟胺酸钴配合物催化对二甲苯氧化的研究

利用羟胺酸BPHA(N 苯甲酰基 N 苯基羟胺)钴配合物Co(BPHA)2作催化剂,对对二甲苯液相氧化反应进行了研究.详细考察了反应温度、催化剂浓度、配体浓度、反应时间和轴配体对该催化反应的影响.实验结果表明:当反应温度为125℃、氧气压力为0.5MPa、催化剂浓度为1.0×10-3mol/L、配体与催化剂的摩尔比为2∶1时、添加四甘醇或聚乙二醇作配体,反应2h时对二甲苯转化率可达41～43%、选择性为92%.本研究丰富了二甲苯选择性氧化的内容,并具有一定的工业应用前景.     

Soluble Congeners of Prior Insoluble Shape-Persistent Imine Cages

One of the most applied reaction types to synthesize shape-persistent organic cage compounds is the imine condensation reaction and it is assumed that the formed cages are thermodynamically controlled products due to the reversibility of the imine condensation. However, most of the synthesized imine cages reported are formed as precipitate from the reaction mixture and therefore rather may be kinetically controlled products. There are even examples in literature, where resulting cages are not soluble at all in common organic solvents to characterize or study their formation by NMR spectroscopy in solution. Here, a triptycene triamine containing three solubilizing n-hexyloxy chains has been used to synthesize soluble congeners of prior insoluble cages. This allowed us to study the formation as well as the reversibility of cage formation in solution by investigating exchange of building blocks between the cages and deuterated derivatives thereof.     

Synthesis of Benzimidazoles via Iron-Catalyzed Aerobic Oxidation Reaction of Imine Derivatives with o-Phenylenediamine

A simple and efficient protocol for preparing benzimidazoles via Fe(NO₃)₃ · 9H₂O-catalyzed aerobic oxidation reaction of imine derivatives with o-phenylenediamine. This process uses air as an economical and green oxidant, tolerates a wide range of substrates, and affords the targeted benzimidazoles in moderate to excellent yields.     

水解胶原蛋白热氧化及CaSO4形成机理探讨

水解胶原蛋白热氧化及CaSO4形成机理探讨;水解胶原蛋白; L-抗坏血酸; H2O2; 热氧化; CaSO4     

Formation of a disordered layer lattice during the intercalation of water into anhydrous vanadyl phosphate

The course of intercalation of water into ₁-VOPO₄ has been studied by thermomechanical analysis and X-ray diffraction. Neither formation of vanadyl phosphate monohydrate nor staging were observed during the intercalation. The broadening and the shift of the positions of the lines in the diffractograms have been explained by the random stacking of intercalated and nonintercalated layers in the sample.     

Reaction of Nitro-Substituted Donor-Acceptor Cyclopropanes with Pyrazoles in DMSO: Unexpected Formation of Tandem Kornblum-Type Ring-Opening Oxidation/Aza-Michael Addition Products

The ring-opening reaction of nitro-substituted donor-acceptor cyclopropanes with pyrazoles in DMSO was investigated. Unexpectedly, the cyclopropanes underwent Kornblum-type ring-opening oxidation with DMSO to form aroylmethylidene malonates as intermediates in the reactions. The intermediates further underwent aza-Michael addition with pyrazoles in tandem manner to give the corresponding aza-Michael adducts. The highlights of the methodology include the occurrence of ring-opening/oxidation under neutral conditions with DMSO and formation of aza-Michael adducts with pyrazoles under catalyst-free conditions.     

Scandium-Mediated Formation of a Bis(tetrahydropentalene)

The reactivity of Li[Sc(COT′′)₂] ( 1 ; COT′′=1,4-bis(trimethylsilyl)cyclooctatetraenyl) towards CoCl₂ is considerably different from that of related lanthanide triple-decker sandwich complexes. In addition to the expected triple-decker complex Sc₂(COT′′)₃ ( 2 ), the complex Sc₂{μ-BTHP}(COT′′)₂ ( 3 ) is formed, which comprises the novel BTHP²⁻ ligand (BTHP²⁻=bis(3,5-bis(trimethylsilyl)-1,3a,6,6a-tetrahydropentalene-1-yl)diide or bis(2,7-bis(trimethylsilyl)bicyclo[3.3.0]octa-2,7-dien-4-yl)diide, C₁₆H₁₀(SiMe₃)₄²⁻). The formation of 3 is likely facilitated by the fact that scandium prefers η⁸,η³ coordination rather than highly symmetric η⁸,η⁸ coordination, and the η³-coordinated COT′′ ligand in 1 is activated owing to a loss of aromaticity. Acid hydrolysis of 3 leads to air-stable H₂BTHP ( 4 ).     

Oxidation behaviour of precipitation hardened steel TG,X-Ray,XRD and SEM study

In the present work the oxidation behavior of ageing treated steel was examined up to 1000°C in different environments (O₂ and CO₂) and with different heating rates. The examination was conducted by means of thermogravimetric analysis, scanning electron microscopy and X-ray diffraction. In this study it was deduced that in the case of O₂ an oxide scale is formed on top of the steel. The oxidation is uniform and the growth of the scale is more intent at low heating rate. It consist of different Fe, Mn, Mo and Cr oxides which are adjusted in the form of layers. This phenomenon was explained by the different diffusion coefficients of each metal in the already formed scale. Regarding the oxidation in CO₂, the scale formation takes place at a lower temperature than in the case of O₂. Hence the examined substrate is more vulnerable in CO₂.     

Formation and Structural Characterization of Metal Complexes derived from Thiosalicylic Acid

The formation and structural aspects of some metal complexes of thiosalicylic acid (TSA) were studied. The μ‐bridging tetra‐coordinated Ru complex, [Ru(C₆H₄(CO₂)(μ‐S)(H₂O)]₂ ( 1 ) was formed by hydrothermal reaction of TSA with RuCl₃. The complexes [M(dtdb)(phen)(H₂O)]_n ( 2 – 4 ) (M = Zn^II, Co^II, Ni^II, dtdb = 2,2′‐dithiodibenzoate anion, phen = 1,10‐phenanthroline) were obtained by the slow diffusion technique and the in situ S–S bond formation was confirmed by elemental, spectral and X‐ray analysis. Reaction of TSA with CuCl₂ and 2,2′‐bipyridine (bipy) under the slow diffusion technique yielded the dimer [Cu(tdb)(bipy)] ( 5 ) (tdb = thiodibenzoic acid), where the in situ generation of 2,2′‐thiodibenzoic acid was observed.     

Structure of Co-crystals Formation from lmidazolium and Aromatic Ligands

In this study, two new co-crystals based on rigid imidazolium ligand(2,2'-((1,1'-biphenyl)-4,4'-diyl)bis(2H-imidazo[1,5-a]pyridine-4-ium) hexafluorophosphate(L)) and 4,4'-bipyridine(Bpy) and benzene(Ben), formulated as L(Bpy)0.5(co-crystal 1) and L(Ben)(co-crystal 2), were obtained. Crystal data for 1: P1 space group with a = 10.921(4), b = 16.998(6), c = 17.666(6), α = 95.720(7), β = 104.272(7), γ = 93.340(6)°, V = 3150.5(19) 3 and Z = 2; and crystal data for 2: monoclinic C2/m space group with a = 25.90(2), b = 9.631(9), c = 6.371(6), β = 95.26(2)°, V = 1583(2) 3 and Z = 2. Co-crystal 1 was dependent on hydrogen bonds and π...π stacking, while only hydrogen bonds are present in 2. Two new co-crystals were characterized by IR, NMR spectra, thermogravimetric and ultraviolet absorption analyses.     

长链脂肪酸LB膜的X射线衍射研究

利用Langmuir-Blodgett技术制备了硬脂酸、花生酸及其混合酸的多层LB膜。用低角X射线衍射研究了它们的周期结构,硬脂酸和花生酸的LB膜在2θ=0.8°～23°的范围内分别出现13个和12个布拉格衍射峰,由此计算了它们的等同周期。用模型计算了它们衍射峰的强度,得到了与实验一致的衍射强度奇偶起伏的结果。在混合酸的LB膜中,可以观察到等同周期随混合比变化的规律。     

Mononuclear to Polynuclear UIV Structural Units: Effects of Reaction Conditions on U-Furoate Phase Formation

Uranium(IV) complexation by 2-furoic acid (2-FA) was examined to better understand the effects of ligand identity and reaction conditions on species formation and stability. Five compounds were isolated: [UCl₂(2-FA)₂(H₂O)₂]_n ( 1 ), [U₄Cl₁₀O₂(THF)₆(2-FA)₂] ⋅ 2 THF ( 2 ), [U₆O₄(OH)₄(H₂O)₃(2-FA)₁₂] ⋅ 7 THF ⋅ H₂O ( 3 ), [U₆O₄(OH)₄(H₂O)₂(2-FA)₁₂] ⋅ 8.76 H₂O ( 4 ), and [U₃₈Cl₄₂O₅₄(OH)₂(H₂O)₂₀] ⋅ m H₂O ⋅ n THF ( 5 ). The structures were determined by single-crystal X-ray diffraction and further characterized by Raman, IR, and optical absorption spectroscopy. The thermal stability and magnetic behavior of the compounds were also examined. Variations in the synthetic conditions led to notable differences in the structural units observed in the solid state. At low H₂O/THF ratios, a tetranuclear oxo-bridged [U₄O₂] core was isolated. Aging of this solution resulted in the formation a U₃₈ oxo cluster capped by chloro and water ligands. However, at increasing water concentrations only hexanuclear units were observed. In all cases, at temperatures of 100–120 °C, UO₂ nanoparticles formed.     

Unexpected formation of a dimeric cation-anionic complex of hypercoordinated tin in the reaction of bis[(2-oxopyrrolidino)methyl]tin dichloride with AgBF4

A new cation-anionic complex of hypercoordinated tin, {[L₂Sn(OH)]⁺ BF₄ ^?}₂ (L is a bidentate (2-oxopyrrolidino)methyl C,O-chelating ligand), was obtained by the reaction of L₂SnCl₂ with AgBF₄ and structurally characterized by X-ray diffraction analysis. In crystalline form, the BF₄ ^? anions are bound to the dications through O?H...F hydrogen bonds (the H?F distance is 1.78 Å). The octahedral coordination of the Sn atoms is strongly distorted because of a weak additional interaction with solvate molecules of dioxane (the Sn?O distance is 3.16 Å).     

Acid-Promoted Oxygen-Atom Transfer from a Novel Dihydroisoquinoline-Derived Oxaziridine Substituted at Position 1

N-Alkyl-oxaziridines react in the presence of a nucleophile as an oxygenating agent; in the absence of a nucleophile, an isomerization reaction is observed. This study describes the synthesis of two new dihydroisoquinoline oxaziridines and their reactivity in an acid-promoted reaction in the presence and absence of sulfides.     

Unexpected Factors Affecting the Kinetics of Guest Molecule Release from Investigation of Binary Chemical Systems Trapped in a Single Void of Mesoporous Silica Particles

In this work, we present results for loading of well-defined binary systems (cocrystal, solid solution) and untreated materials (physical mixtures) into the voids of MCM-41 mesoporous silica particles employing three different filling methods. The applied techniques belong to the group of “wet methods” (diffusion supported loading – DiSupLo ) and “solvent-free methods” (mechanical ball-mill loading – MeLo , thermal solvent free – TSF ). As probes for testing the guest1-guest2 interactions inside the MCM-41 pores we employed the benzoic acid ( BA ), perfluorobenzoic acid ( PFBA ), and 4-fluorobenzoic acid ( 4-FBA ). The guests intermolecular contacts and phase changes were monitored employing magic angle spinning (MAS) NMR Spectroscopy techniques and powder X-ray diffraction (PXRD). Since mesoporous silica materials are commonly used in drug delivery system research, special attention has been paid to factors affecting guest release kinetics. It has been proven that not only the content and composition of binary systems, but also the loading technique have a strong impact on the rate of guests release. Innovative methods of visualizing differences in release kinetics are presented.     

Dilactone Formation by Chromic Anhydride Oxidation of the Germacranolide Stizolicin

The sidechain of the germacranolide stizolicin was oxidized by CrO₃ in Py to form a lactone. The structure of the product was established as 4,5α-epoxy-7α,5,6,8β(H)-germacr-1(10),11(13)-dien-8α (3′-oxo-2′,5′-dihydrofuran-3′-carboxylyl)-12,6-olide using spectral data.__________Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 117–118, March–April, 2005.     

Unexpected dimeric products from the amidomethylation of pentasubstituted benzenes

An isomeric series of unexpected diarylmethane products with flexible substituents, isolated from amidomethylation reactions of p-dimethoxybenzene derivatives, was analyzed by X-ray crystallography to reveal novel solid-state structures, two of which have identical elemental cell parameters.     

Acid‐Mediated Formation of Radicals or Baeyer–Villiger Oxidation from Criegee Adducts

The acid‐mediated reaction of ketones with hydroperoxides generates radicals, a process with reaction conditions similar to those of the Baeyer–Villiger oxidation but with an outcome resembling the formation of hydroxyl radicals via ozonolysis in the atmosphere. The Baeyer–Villiger oxidation forms esters from ketones, with the preferred use of peracids. In contrast, alkyl hydroperoxides and hydrogen peroxide react with ketones by condensation to form alkenyl peroxides, which rapidly undergo homolytic O? O bond cleavage to form radicals. Both reactions are believed to proceed via Criegee adducts, but the electronic nature of the peroxide residue determines the subsequent reaction pathways. DFT calculations and experimental results support the idea that, unlike previously assumed, the Baeyer–Villiger reaction is not intrinsically difficult with alkyl hydroperoxides and hydrogen peroxide but rather that the alternative radical formation is increasingly favored.