3β-Methoxyolean-18-ene (miliacin) from the marine fungus Chaetomium olivaceum

A pentacyclic tritepenoid, 3-methoxyolean-18-ene (miliacin), was isolated for the first time from the marine fungus Chaetomium olivaceum. Its structure was determined on the basis of 2D NMR spectroscopy and X-ray diffraction data.     

甲基丙烯酸—磷脂酰乙醇甲基丙烯酰胺共聚物LB膜的研究

制备了不同摩尔比的甲基丙烯酸-磷脂酰乙醇甲基丙烯酰胺共聚物,研究了这种共聚物在水面的表面压力(π)-分子面积(A)曲线、共聚物制成的MOS LB膜的电容(C)-电压(V)特性及此LB膜的相变温度。     

Surface mixed adsorption films of 2,4,6- trimethylphenol–2,4,6-trichlorophenol at aqueous solution/air interface

 The results of experimental studies of the adsorption at the solution/air interface from an aqueous mixture: 2,4,6-trimethylphenol–2,4,6-trichlorophenol are presented. The surface properties of the above-mentioned mixture were studied by surface potential and surface tension measurements. These measurements were carried out as a function of the concentration of 2,4,6-trimethylphenol aqueous solution at a constant concentration of 2,4,6-trichlorophenol. Using the results obtained and based on the Gibbs equation, Helmholtz formula and Motomura’s method the relative surface excesses of adsorbed substances, effective dipole moments, surface molar fractions of solutes and miscibility of adsorbed films were determined. Received: 7 November 1997 Accepted: 26 February 1998     

添加非金属元素Si对固体超强酸SO_4~(2-)/TiO_2的改性研究

采用共沉淀法引入Ｓｉ对ＳＯ２－４／ＴｉＯ２进行改性，制得了ＳＯ２－４／Ｔｉ－Ｓｉ－Ｏ系列固体超强酸，试样经ＩＲ、ＳＥＭ、ＸＲＤ表征和低温正戊烷异构化活性测试，发现超强酸中心是硫酸根离子与金属原子Ｔｉ结合形成的双配位螯合结构，在超强酸性的样品中ＴｉＯ２均呈锐钛矿晶型。引入Ｓｉ仅迟滞ＴｉＯ２晶化过程，控制Ｓｉ在ＳＯ２－４／Ｔｉ－Ｓｉ－Ｏ体系中的含量可以有效调节固体超强酸的酸性，并提高正戊烷异构化反应的选择性。     

CexTi1-xO2复合氧化物的结构及负载CuO对NO还原性能研究

采用共沉淀法制备了不同摩尔比(x=0,0.1,0.2～0.9,1.0)的CexTi1-xO2复合氧化物,考察了CuO/CexTi1-xO2对NO+CO反应的活性,并用BET,TPR和XRD等技术对各试样进行了表征。结果表明,试样的结构和还原特性随焙烧温度变化而变化。XRD检测表明,x值从0.1增加到0.5时,650℃焙烧的试样已形成了CeTi2O6物相,且主要以无定形状态存在;试样经800℃焙烧后晶化完全;x>0.6时,一些TiO2已经进入了CeO2晶格,形成了Ce Ti固溶体。催化剂活性评价表明CuO/CexTi1-xO2(650℃)对NO+CO反应具有较好的活性,其活性随x值变化而变化。TPR及XRD结果表明CuO与CeTi2O6之间存在很强的相互作用,CeTi2O6物相的形成使CuO的还原峰温由380℃提前到200℃,而CuO的存在又促进CeTi2O6的还原峰温从600℃提前至200～300℃。     

Reaction kinetics of the selective liquid phase hydrogenation of styrene oxide to β-phenethyl alcohol

Liquid phase hydrogenation of styrene oxide using 1% Pd/C and NaOH as a promoter was found to give selectively β-phenethyl alcohol (PEA) under very mild conditions (313–333 K; 0.68–5.5 MPa). The kinetics of this system was investigated by collecting initial rate data in a batch slurry reactor. Rate of hydrogenation was found to decrease beyond a certain concentration of both hydrogen (>3 MPa) and styrene oxide (>0.5 kmol/m³). A Langmuir–Hinshelwood type rate equation has been proposed based on the initial rate data in the kinetic regime. The model predictions agree very well with the experimentally observed concentration–time data indicating the applicability of the proposed rate model.     

Friedel-crafts acylation of 2-methoxynaphthalene over h-beta catalysts: effect of Si/Al ratio

The acylation of 2-methoxynaphthalene with acetic anhydride was carried out over zeolite beta catalysts having various Si/Al ratios. It was found that the reaction performance is strongly dependent on the Si/Al ratio of the catalyst. The catalytic reaction features were elucidated in terms of the acidic properties of the catalysts. This revised version was published online in June 2006 with corrections to the Cover Date.     

Molecule-Responsive Fluorescent Sensors of α-Helix Peptides Bearing α-Cyclodextrin, Pyrene and Nitrobenzene Units in Their Side Chains

-Helix peptides bearing one unit of -cyclodextrin (-CD), one unit of pyrene and one unit of nitrobenzene (NB) in their side chains have been designed and synthesized as novel molecule-responsive devices.In both the CD-peptides, -PR17 and -PL17, the NB unit is separated from the CD unit by two turns of the helix. Two reference peptides (PL17, and -P17,) have also been synthesized. The circular dichroism studies in the peptide absorption region (200–250 nm)of -PR17 and -PL17 suggestthat the CD-peptides form stable-helixstructures (83–77%), which was destabilized by accommodating guest molecules (e.g., n-pentanol) into the CD cavity. It suggests that formation of intramolecular host–guest(CD–NB) complex stabilized thehelical structure and exogenous guest molecule excluded the appending NB moiety from inside to outside of the CD cavity, thereby causing destabilization of the helical structure and increasing the random coil content. The ICD spectra of the peptides in the pyrene and nitrobenzene absorption region (250–40 nm) suggest that NB forms inclusion complex with CD. The fluorescence studies revealed that the fluorescence of the pyrene unit is quenched by the NB unit in -PR17 and -PL17. The fluorescence intensity increases with increasing guest concentration for the CD-peptides.This guest-responsiveenhancement in the fluorescence intensity can be explained in terms of increased distance between the pyrene and NB moieties, which is caused by exclusion of the NB moiety from the CD cavity by guest accommodation. Using the guest-responsive fluorescence quenching properties of the CD-peptides, we have obtained binding constants for various short chain alkanols. -PL17 has higher binding affinity to the guest molecules than its isomer, -PR17, indicating that the location of functional groups on the peptide scaffold is important in molecule detection.     

Trace level analysis of volatile and semi-volatile organic compounds in water using a membrane/jet separator interfaced to an ion trap mass spectrometer

An ion trap mass spectrometer, equipped with a membrane/jet separator interface, is used for the direct detection of volatile and semi-volatile organic compounds in aqueous solutions. Aqueous sample is passed through a capillary membrane, the outside surface of which is continuously purged by helium. The permeate is pneumatically transported to the mass spectrometer via a jet separator which acts as an additional enrichment device. The performance and response characteristics of non-porous silicone and microporous polytetrafluoroethylene (PTFE) membranes are studied. The microporous membrane allows sufficient water to pass for it to be used as a reagent gas for chemical ionization. Both types of membranes provide detection limits in the parts per trillion (pptr) to parts per billion (ppb) range with a linear dynamic range of 3 orders of magnitude for some volatile organic compounds. Results show that there is no detectable matrix effect on response in the selected cases examined. The use of microporous membranes to analyze more polar compounds, such as 5-hydroxymethyl furfuraldehyde and lactic acid, is also demonstrated. The effects of other experimental parameters, such as membrane temperature and length, on sensitivity are also investigated.     

Hydrogen transport through Pd-Ni alloy electrodeposited on Pd substrate

Hydrogen transport through a Pd-Ni alloy electrodeposited on a Pd substrate (Pd-Ni/Pd bilayer symmetric electrode) has been investigated using cyclic voltammetry and a.c. impedance spectroscopy combined with the electrochemical hydrogen permeation method. The permeation build-up current transients and the measured impedance spectra were analyzed using the time-lag method for the bilayer electrode and a complex non-linear least squares data-fitting method based upon the derived Faradaic admittance for the hydrogen absorption into and diffusion through the bilayer electrode under the permeable boundary condition, respectively. The value of the hydrogen diffusivity in the Pd-Ni layer was lower than that in the Pd layer. Furthermore, the values of the charge transfer resistance and equilibrium absorption constant for the Pd-Ni/Pd bilayer electrode were higher than those for the Pd single layer electrode. From the experimental results, the role of the thin Ni(OH)₂ film formed on the Pd-Ni layer surface in the hydrogen transport through the Pd-Ni/Pd bilayer electrode is discussed in terms of its passivating effect and extremely large hydrogen solubility. Received: 22 January 1997 / Accepted: 15 April 1997