New prenylated C₆-C₃ compounds from the twigs of Illicium anisatum

Two new prenylated C?-C? compounds, cycloillicinone (1) and 4-allyl-2-methoxy-6-(2-methylbut-3-en-2-yl)phenol (2), were isolated from the twigs of Illicium anisatum, and their structures were determined by 2D-NMR methods. Cycloillicinone (1) is a unique prenylated C?-C? that is appended with an additional geranyl unit. Compound 2 was found to show moderate neurite-outgrowth promoting activity in primary cultured rat cortical neurons at a concentration of 10 μM.     

Polyoxypregnanes from the stems of Marsdenia tenacissima

From the stems ofMarsdenia tenacissima two new polyoxypregnanes were isolated, their structures were elucidated by 1D, 2D-NMR as 11α,12β-di-O-tigloyl-tenacigenin B （1） and tenacigenoside E （2）.     

A new cycloartane triterpenoid from the leaves and stems of Fritillaria hupehensis

A new triterpenoid has been isolated from the leaves and stems of Fritillaria hupehensis Hsiao et K.C.Hsia.Its structure wasestablished as(23Z)-9,19-cycloart-23-ene-3α,25-diol 1 through chemical and spectroscopic studies including 2D NMR.Anotherknown triterpenoid 9,19-cycloart-25-ene-3β,24ξ-diol 2 was also isolated.     

Two Novel Epimeric Eremophilane Sesquiterpenes from the Flower of Cacalia tangutica

Two novel epimeric eremophilane sesquiterpenes, 7β-H-3α-angeloyl-9(10)-ene-11,12-epoxy-8-oxoeremophilane (1) and 7β-H-3α-angeloyl-9(10)-ene-11, 12-epoxy-8-oxoeremophilane (2) were isolated from the methanol extract of the flower of Cacalia tangutica (Franch.) Hand-Mazz. Their structures were characterized by 1D-, 2D-NMR (^1H-^1H COSY, HMQC, HMBC, ^1H-^1H NOESY) and HRESI-MS techniques.     

Thermodynamic scaling of α-relaxation time and viscosity stems from the Johari-Goldstein β-relaxation or the primitive relaxation of the coupling model

By now it is well established that the structural α-relaxation time, τ(α), of non-associated small molecular and polymeric glass-formers obey thermodynamic scaling. In other words, τ(α) is a function Φ of the product variable, ρ(γ)/T, where ρ is the density and T the temperature. The constant γ as well as the function, τ(α) = Φ(ρ(γ)/T), is material dependent. Actually this dependence of τ(α) on ρ(γ)/T originates from the dependence on the same product variable of the Johari-Goldstein β-relaxation time, τ(β), or the primitive relaxation time, τ(0), of the coupling model. To support this assertion, we give evidences from various sources itemized as follows. (1) The invariance of the relation between τ(α) and τ(β) or τ(0) to widely different combinations of pressure and temperature. (2) Experimental dielectric and viscosity data of glass-forming van der Waals liquids and polymer. (3) Molecular dynamics simulations of binary Lennard-Jones (LJ) models, the Lewis-Wahnstr?m model of ortho-terphenyl, 1,4 polybutadiene, a room temperature ionic liquid, 1-ethyl-3-methylimidazolium nitrate, and a molten salt 2Ca(NO(3))(2)·3KNO(3) (CKN). (4) Both diffusivity and structural relaxation time, as well as the breakdown of Stokes-Einstein relation in CKN obey thermodynamic scaling by ρ(γ)/T with the same γ. (5) In polymers, the chain normal mode relaxation time, τ(N), is another function of ρ(γ)/T with the same γ as segmental relaxation time τ(α). (6) While the data of τ(α) from simulations for the full LJ binary mixture obey very well the thermodynamic scaling, it is strongly violated when the LJ interaction potential is truncated beyond typical inter-particle distance, although in both cases the repulsive pair potentials coincide for some distances.     

Two new compounds from the stem of Vernonia cumingiana

Two new compounds vemonioside S and vemoniether S were isolated from the stem of Vernonia cumingiana, and their structures were elucidated on the basis of spectroscopic evidences.     

Supramolecular compounds constructed from Keggin anions and metal–organic complex cations of 3-aminopyrazine-2-carboxylic acid

Three new supramolecular compounds based on Keggin-type polyoxometalate (POM) and transition metal complexes, [M(Hapca)₂(H₂O)₂]₂[SiW₁₂O₄₀]·nH₂O, (M = Ni^II(1), Zn^II(2), n = 12; Co^II (3), n = 15; Hapca = 3-aminopyrazine-2-carboxylic acid), have been synthesized in aqueous solution and characterized by single-crystal X-ray diffraction, elemental analysis, TG analyses, IR and fluorescence spectroscopy. The X-ray structrual analysis reveals that three compounds are isostructural with a P21/c space group. [M(Hapca)₂(H₂O)₂] ₂ ⁴⁺ are linked together via O···N hydrogen-bonding interaction to give birth to 2D layer with rectangle grids. Anions [SiW₁₂O₄₀]^4? are located in the cavities and link the 2D layers into 3D supramolecular architecture via hydrogen bonds. The compounds represent the first examples of self-assembly of 2D metal–Hapca complex supramolecular “host” networks formed by hydrogen bonding interactions and “guest” polyoxoanion species. In addition, solid-state luminescence properties of compounds 2 and 3 have been studied at room temperature.     

Sesquiterpenes from the fruits of Illicium Simonsii maxim

Abstract

A new allo-cedrane sesquiterpene glycoside (1) and nine known compounds (2–10) were isolated from the ethanol extract of the fruit of Illicium simonii Maxim. Their structures were elucidated by spectroscopic methods, including 1D-, 2D-NMR, and HRESIMS. The absolute configuration of compound 1 was confirmed by CD experiments. Among them, compounds 1, 4, 5, and 7 displayed moderate anti-inflammatory activities by use of an in vitro bioassay.     

The Catalytic Dehydrogenation of c2h6 to c2h4 under non-Oxidative Conditions over the 6cr/g-al2o3Catalyst

In the present paper, the catalytic dehydrogenation of C₂H₆ to C₂H₄ under non-oxidative conditions was investigated in a fixed-bed micro-reactor under ambient pressure at 823 - 923 K. The 6Cr/g-Al₂O₃ catalyst was found to be the best catalyst among the g-Al₂O₃, SiO₂, MCM41, MgO and Si-2 supported chromium oxide catalysts. The features of the 6Cr/g-Al₂O₃ catalyst for the reaction could be listed as follows: (1) At 823 - 923 K, the C₂H₄ selectivity of 92.5-78.6% at a C₂H₆ conversion of 9.5-29.8% could be obtained. (2) The catalyst had the good regeneration performance, i.e., could be regenerated by air repeatedly. (3) The main products were C₂H₄, CH₄, H₂ and coke. No carbon oxides were identified.     

Dipole polarizability pseudospectra and C6 dispersion coefficients for H2–H2

Pseudostate decomposition of static dipole polarizabilities for ground state H₂⁺ from a Givens-Householder diagonalization of the excitation operator (

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H" height="17" width="20">₀−E₀) over an N-term basis of appropriate symmetry allows for a rapidly convergent evaluation of C₆ dispersion coefficients for H₂⁺–H₂⁺. 27-term pseudospectra of hypergeneralized James functions with a 30-term GGJ⁺ unperturbed wavefunction with an optimized scale factor δ=0.918 at R=2₀ give C₆ and γ₆ values that are accurate to no less than nine significant figures.     

The role of surface species on the SCR of NO by C3H6 under lean-burn conditions over platinum catalyst

The nature of the surface species on Pt/Al₂O₃ for the SCR of NO by C₃H₆ under excess oxygen has been investigated. An experiment consisting of three steps shows that there are at least three types of surface species occurring on the catalyst surface. However, a reactivity test and an investigation of surface species after adding a second metal (Fe, Sn, Co, Cr or W) to Pt/Al₂O₃ indicate that only (C_lH_mO_n)_HT species play an important role in NO reduction at a low operating temperature. This revised version was published online in June 2006 with corrections to the Cover Date.     

Co/Fe/Al2O3/cordierite催化C3H6选择性还原NO的实验研究

采用溶胶凝胶法和浸渍法制备了负载于蜂窝陶瓷上的Co/Fe/Al₂O₃/cordierite催化剂,在陶瓷管流动反应器上对其催化C₃H₆选择性还原NO的性能进行了测试。结果表明,该催化剂表现出最优脱硝性能,在模拟烟气条件下,当反应温度为550 ℃时可实现97%的脱硝效率。Co的引入可显著增强Fe/Al₂O₃/cordierite催化剂抗SO₂和H₂O的能力。在模拟烟气中同时引入0.02% SO₂和3% H₂O后,1.5Co/Fe/Al₂O₃/cordierite的脱硝性能受影响甚微,当反应温度高于500 ℃时1.5Co/Fe/Al₂O₃/cordierite催化C₃H₆还原NO的效率均可达到90%以上;相比之下,未经Co修饰的催化剂Fe/Al₂O₃/cordierite脱硝性能受到了严重的抑制,在整个反应温度区间（200-700 ℃）内,其催化C₃H₆还原NO的效率最高不足50%。XRD和SEM表征结果表明,经过适量的Co修饰后的1.5Co/Fe/Al₂O₃/cordierite表面变得更疏松,且形成了以钴铁和钴铝双金属氧化物为主要成分的球状晶粒。H₂-TPR结果表明,相比于Fe/Al₂O₃/cordierite,1.5Co/Fe/Al₂O₃/cordierite有更好的低温还原性能。Py-FTIR结果表明,Co的引入可使催化剂表面的Lewis酸明显增加,且生成了Brønsted酸。N₂吸附-脱附表征结果表明,Co可增大催化剂的比表面积。     

NO reduction with C3H8 on Co/Al2O3 catalyst. effect of O2 concentration

The selective catalytic reduction (SCR) of NO by propane in excess oxygen-containing gas mixture was studied on Co/Al₂O₃ catalyst. The oxygen concentration is very important for the reaction. The NO conversion to N₂ without oxygen is 3% at 800 K and when the O₂ concentration is raised up to 8% the NO conversion reaches its maximum value of 60% at 800 K. Characterization results by TPR and UV-Vis spectroscopy show that in the catalyst, species strongly interacting with tetrahedral and octahedral Co²⁺ ions in the support are present. This revised version was published online in June 2006 with corrections to the Cover Date.     

Singlet and triplet potential energy surfaces of C3H2

The detailed singlet and triplet potential energy surfaces of C₃H₂ involving nine isomers and 13 transition structures are studied at the G3 level of theory. The rearrangement mechanisms and the electronic properties of various isomers in a broad energy range have been studied in both singlet and triplet states. Cyclopropenylidene and propargylene are found to be the most stable isomers in the singlet and triplet states, respectively. The singlet isomers are found to be more kinetically stable species as a result of high conversion barriers through which they pass. The calculations indicate that cyclopropyne in its triplet state is the least kinetically stable isomer. It is realized that the G3 method comprises both computational cost and accuracy and thus can be applied to investigation of potential energy surface of small molecules.     

Structures and energetics of C3H6S isomers: a Gaussian-3 ab initio study

Twenty-two isomers/conformers of C₃H₆S^+√ radical cations have been identified and their heats of formation (ΔH_f) at 0 and 298 K have been calculated using the Gaussian-3 (G3) method. Seven of these isomers are known and their ΔH_f data are available in the literature for comparison. The least energy isomer is found to be the thioacetone radical cation (4⁺) with C_2v symmetry. In contrast, the least energy C₃H₆O^+√ isomer is the 1-propen-2-ol radical cation. The G3 ΔH_f298 of 4⁺ is calculated to be 859.4 kJ mol⁻¹, ca. 38 kJ mol⁻¹ higher than the literature value, ≤821 kJ mol⁻¹. For allyl mercaptan radical cation (7⁺), the G3 ΔH_f298 is calculated to be 927.8 kJ mol⁻¹, also not in good agreement with the experimental estimate, 956 kJ mol⁻¹. Upon examining the experimental data and carrying out further calculations, it is shown that the G3 ΔH_f298 values for 4⁺ and 7⁺ should be more reliable than the compiled values. For the five remaining cations with available experimental thermal data, the agreement between the experimental and G3 results ranges from fair to excellent.

Cation CH₃CHSCH₂^+√ (10⁺) has the least energy among the eleven distonic radical cations identified. Their ΔH_f298 values range from 918 to 1151 kJ mol⁻¹. Nevertheless, only one of them, CH₂=SCH₂CH₂^+√ (12⁺), has been observed. Its G3 ΔH_f298 value is 980.9 kJ mol⁻¹, in fair agreement with the experimental result, 990 kJ mol⁻¹.

A couple of reactions involving C₃H₆S^+√ isomers CH₂=SCH₂CH₂^+√ (12⁺) and trimethylene sulfide radical cation (13⁺) have also been studied with the G3 method and the results are consistent with experimental findings.     

时间分辨红外发射光谱研究C2H3+NO反应体系

The elementary reaction of C2H3＋ NO has been reported for the first time in this paper.C2H3 radical was produced by laser photolysis of vinyl bromide at 248 nm. Vibrationally excited reaction products H2CO,NCO and HCN were observed. Two exothermic reaction channels leading to HCN＋ H2CO and CH3＋ NCO are identified.     

H6PMo9V3O40/SiO2催化剂催化酚类化合物选择性硝化

为创建洁净高效的酚类化合物硝化工艺,以杂多酸H6PMo9V3O40(PMAV3)为活性组分,硅胶为载体,浸渍法制备了负载型催化剂PMAV3/SiO2,采用红外光谱、X射线衍射谱、N2吸附-脱附法及TG-DSC分析等测试技术对该催化剂的结构及热稳定性进行了表征;考察了该催化剂对多种酚类化合物硝化反应的催化性能。结果显示,该催化剂对多种酚类化合物的硝化反应具有很强的催化活性和区域选择性,产率为83.7%~94.5%,其中苯酚、邻甲酚、邻氯苯酚和邻氟苯酚以邻位硝化产物居多,水杨酸的对位硝化产物占绝对优势;负载催化剂的织构性质与载体相近,但随负载量增加,比表面积逐渐降低;PMAV3/SiO2的热稳定性好于本体PMAV3。催化剂回收容易,重复使用5次,活性基本不变。