Features of clathrate formation of <Emphasis Type="Italic">trans</Emphasis>-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid

Structural data illustrating various ways of association of the molecules of host and guest observed in the clathrates of trans-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid (DED) with chloroform, ethyl propionate, 1,4-dioxane and acetone are presented. The following types of host-guest interactions are considered: “true clathrate” without host-guest hydrogen bonds (DED + chloroform, DED + ethyl propionate), infinite associate (DED + 1,4-dioxane) and discrete associate (DED + acetone).     

X-ray structure of lagochirsine

The molecular structure of the lagochilin diterpenoid lagochirsine was determined by x-ray structure analysis. The crystallographic investigations were conducted on an automated four-circle STOE/STAD14 diffractometer at room temperature. The crystals were trigonal, space group P3₂ (No. 145), C₂₀H₃₂O₅, a = b = 14.289(2) Å, c = 8.2320(16) Å, V = 1455.6(4) ų , Z = 3, D_calc = 1.206 g/cm³, R = 0.065 (R_w = 0.1368).Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 398–400, September–October, 2004.     

波长色散X射线荧光光谱法测定钴精矿中钴、铜和锰含量

采用高纯氧化物经四硼酸锂和偏硼酸锂熔融制备人工标准样品,以氧化镱为内标,制作校准曲线,建立了波长色散型X射线荧光光谱法测定钴精矿中钴、铜、锰元素的分析方法。重点研究了混合熔剂、试样稀释比、氧化剂和内标选择、方法检出限、方法准确度和精密度等,结果表明,各元素校准曲线线性范围宽,相关系数均大于0.999, 钴、铜、锰元素检出限分别达到0.002%、0.001%和0.001%,测试准确度和精密度可靠,方法满足行业检测需求。     

蒙药草乌花及其提取物化学成分的红外光谱法整体结构解析

采用傅立叶变换红外光谱法并借助于二阶导数谱以及二维相关红外光谱(2D-FTIR)研究了蒙药草乌花原药材及不同溶剂提取物(依次采用乙醚,乙醇和水提取)所含化学成分的红外谱图整体变化规律.结果显示:在草乌花原药材中具有明显的多糖类化合物的红外特征吸收峰,证明该药材中含有大量多糖类成分.草乌花药材乙醚和醇提物的红外光谱较相似...     

回归正交试验设计在水飞蓟素提取工艺中的应用

本文针对水飞蓟素提取工艺利用二次回归正交设计 ,进行了五个变量的正交回归设计 ,获得了最佳的试验工艺参数值以及相应的数学模型     

Analyzing dynamic interaction of impulse-loaded strips

The paper considers the dynamic process of contact interaction of infinite impulse-loaded strips arranged with a gap. The behavior of the strips is described by linear elastic dynamics equations. The contact problem is solved by the collocation method. The process of impact of two and three strips is analyzed. The calculation results are compared with data obtained by using the finite-element method.     

反相高效液相色谱法测定棒柄花中反式-4-(1-丙烯基)苯酚-β-D-吡喃葡萄糖苷

用反相高效液相色谱法建立棒柄花中反式-4-(1-丙烯基)苯酚-β-D-吡喃葡萄糖苷的含量测定方法,并测定其含量。色谱柱Reliasil-C18(250 mm×4.6 mm,5μm),流动相乙腈-水(体积比22∶78),流速1.0mL/m in,检测波长257 nm。结果待测组分在0.080 4~0.281 4μg范围内与峰面积线性关系良好,相关系数为0.999 5,平均加标回收率为98%,RSD为1.8%(n=6)。本法简便、快速、重复性好、结果准确可靠。     

Synthesis and Activity of Nanodispersed SnO2–CeO2 Catalyst in the Oxidation Reactions of Carbon Monoxide and Methane

Kinetics and Catalysis - Nanodispersed SnO2–CeO2 catalysts for the oxidation of CO and СН4 were synthesized by coprecipitation in a water–isopropanol solution followed by...     

Crystal structure of three solvates of 1,1′-binaphthyl-2,2′-bicarboxylic acid with 2-picoline

From solutions in 2-picoline (2-methylpyridine), depending on the temperature of crystallization, the universal clathratogen — 1,1′-binaphthyl-2,2′-bicarboxylic acid (BBA) — precipitates as crystals of three types with different composition and structure. Under normal conditions (room temperature), the precipitate is crystals of BBA disolvate with 2-picoline; a temperature reduction of 20°C results in the crystallization of monosolvate dihydrate; and a temperature increase of the same level results in the precipitation of monosolvate. That is, as the temperature of crystallization rises, the number of included guest molecules gradually decreases and the space where they are located becomes more closed. In 1:1:2 BBA/2-picoline/H₂O solvate (space group P2₁/n, a = 11.991(2) Å, b = 9.317(2) Å, c = 22.283(5) Å, β = 99.77(3)○, V = 2453.3(9) ų, Z = 4), the carboxyl groups of the BBA molecule at the C21 atom are deprotonated and the released proton goes to the nitrogen atom of 2-picoline. BBA molecules interact with those of 2-picoline and water via H bonds to form infinite chains in direction [111], which, in their turn, join together into infinite two-dimensional sheets parallel to plane (?101). 2-Picoline molecules are located in the channels. In BBA/2-picoline disolvate (space group C ₂/c, a = 11.7523(11) Å, b = 13.8563(13) Å, c = 17.9615(13) Å, β = 108.044(9)○, V = 2781.1(4) ų, Z = 4), one BBA molecule and two H bond 2-picoline molecules form a 0-dimensional associate of the type G-H-G. The solvent molecules are also located in the channels. In BBA/2-picoline monosolvate (space group P2₁/c, a = 9.299(5) Å, b = 12.727(5) Å, c = 19.011(5) Å, β = 95.248(5)○, V = 2240.5(16) ų, Z = 4), each BBA molecule is H-bonded with a 2-picoline molecule to form a 0-dimensional associate of the type H-G. Guest molecules are located in closed cavities.     

Experimental Solution of the Local Field Problem in Uniaxial Liquid Crystals†

A method of experimental determination of the Lorentz-factor tensor in uniaxial liquid crystals is suggested. The specific features of the local field tensor of the light wave in a nematic liquid crystal with low optical anisotropy have been investigated experimentally. Anisotropy of the local field and Lorentz-factor tensors has been found to decrease with the decreasing optical and molecular-optical anisotropies. These results appear to contradict the existing polarization theories of liquid crystals. The local field problem in cholesteric liquid crystals has been considered. A new approach to the local field problem in uniaxial liquid crystals with arbitrary optical anisotropy is developed and the experimental results are explained.