Studies on the Synthesis of a Natural Product—Piceatannol and its Analogs

Piceatannol,(E)-3,3′,4,5′-tetrahydroxy stilbene, a natural polyhydroxy stibene, possesses many biological activities, its synthesis has been reported. We designed another route of its synthesis, which can be controlled more easily. The synthetic product was characterized by elemental analysis,IR,MS and ^1H-NMR. Its analogs were synthesized by the similar method.     

Visions of the electrochemical future,past and present: Plus ca change?

Journal of Solid State Electrochemistry -     

Studies on Synthesis of a Cycloheptapeptide and Effects of Different Metal Ions on the Cyclization

ＩｎｔｒｏｄｕｃｔｉｏｎＣｙｃｌｉｃｐｅｐｔｉｄｅｓ ,ｗｈｉｃｈａｒｅｃｏｎｓｔｒａｉｎｅｄｃｏｎｆｏｒｍａ ｔｉｏｎａｌｌｙａｎｄｍｏｒｅｒｅｓｉｓｔａｎｔｔｏｐｒｏｔｅａｓｅｄｉｇｅｓｔｉｏｎｓｔｈａｎｔｈｅｉｒｌｉｎｅａｒｐｒｅｃｕｒｓｏｒｓ ,ｈａｖｅｂｅｅｎｏｆｇｒｅａｔｉｎｔｅｒｅｓｔａｓｓｙｎｔｈｅｔｉｃｔａｒｇｅｔｓｂｏｔｈａｓｐｏｔｅｎｔｉａｌｄｒｕｇｌｅａｄｓａｎｄａｓｍｏｄｅｌｓｆｏｒｃｏｎ ｆｏｒｍａｔｉｏｎａｌａｎａｌｙｓｉｓ .1 4 Ｃｕｒｒｅｎｔｍｅｔｈｏｄｓｆｏｒｓｙｎｔ…     

Studies on the thermodynamics of exchange in clays—III Nickel exchange on Na-, Ca- and Mg-Montmorillonites

Exchange equilibria involving Ni ions on Na-, Ca- and Mg-montmorillonites were studied with the help of the thermodynamic models of earlier workers. The exchange isotherms and free energy changes were indicative of a lower preference of Ni for the base saturated montmorillonites. The exchange was in accordance with the Hofmeister series. Enthalpy changes indicated a stronger binding of Ni on Ca- and Mg-montmorillonites than on Na-clay. Entropy findings were indicative of a dehydrated and disordered arrangement of Ni ions during their adsorption on Na-montmorillonite. The effect of dehydration on the entropy was the reverse in the case of Ca- and Mg-montmorillonites. The diversity of the exchange equilibria involving Ni, Na, Ca and Mg ions on the montmorillonite surface was further confirmed from our observations on the activity coefficients and the values of ΔG_m^x, ΔH_m^x and ΔS_m^x.     

Studies on the Syntheses of the Side Chains of Brassinolide and Dolicholide

(4R,5S)-2,2-Dimethyl-4-(1',2'-dimethylpropyl)-5-(1'-bromoethyl)--1,3-dioxolane(15) with the side chain of brassinolide and (4R, 5S)--2, 2-dimethyl-4-(l'-methylene-2'-methylpropyl)-5-(1'-bromoethyl) 1,3-dioxolane(14) with the side chain of dolicholide were first synthesized through 11 and 10 stepes from D-mannitol respectively. All of the intermediates 7-13 were first synthesized too.     

Studies on the Protonation and Complexations of Dioxotetraamine Macrocycles

ＳｔｕｄｉｅｓｏｎｔｈｅＰｒｏｔｏｎａｔｉｏｎａｎｄＣｏｍｐｌｅｘａｔｉｏｎｓｏｆＤｉｏｘｏｔｅｔｒａａｍｉｎｅＭａｃｒｏｃｙｃｌｅｓＳｔｕｄｉｅｓｏｎｔｈｅＰｒｏｔｏｎａｔｉｏｎａｎｄＣｏｍｐｌｅｘａｔｉｏｎｓｏｆＤｉｏｘｏｔｅｔｒａａｍｉｎｅＭａ...     

Theoretical Studies on the Relationship Between the Structure and Property of Cellulose and Nitrocellulose——Nitration Activity and Mechanism

Many derivatives of industrially useful cellulose have hydroxyls of the anhydroglucose(AHG) units uncompletely substituted. Since each AHG unit of a cellulose molecule is a trihydric alcohol,consisted of one primary(position 6) and two secondary hydroxyl groups(positions 2 and 3), the distribution of substituents in these trihydric alcohol units could be different for different derivatives. The     

Studies on the Synthesis and the Structure of Ferric Aluminum Magnesium Hydrotalcite—like Compounds

Hydrotalcite-like compounds (HTlc) are composed of trivalent and divalent metal ions, the general formula 1 is: [M2+1-xM3+x(OH)2]x+An-x/n·mH2O M3+ is trivalent metal ions, M2+is divalent metal ions, A is negative ions whose valence is n, and m is the amount of water in the crystal, and x is the molar ratio of trivalent metal ions to all metal ions. A lot of studies have been done on the synthesis and property of HTlc, which is made up of two kinds of the metal ions. It has been found …     

Studies on the biosynthesis of arteannuin——Ⅳ.The biosynthesis of arteanniuin and arteannuin B by the leaf homogenate of Artemisia annua L.

Arteannuic acid and(-)11R,13-d ydroarteannuic acid are the key intermediates in thebiosynthesis of arteannuin by the leaf homogenate of Artemisia annua L.,and arteannuic acid andepoxyarteannuic acid are the intermediates of arteannuin B.and epoxyarteannuic acid can not betransformed into arteannuin by the homogenate.     

Studies on the curing and thermal behaviour of diglycidyl ether of bisphenol-A (DGEBA) in the presence of aromatic diimide–diacids

This paper describes the synthesis and characterization of aromatic diimide–diacids (DIDAS) obtained by reacting pyromellitic dianhydride (PMDA), 4,4′-oxo diphthalic anhydride (ODA), 1,4,5,8-naphthalene tetra carboxylic dianhydride (NTDA) with excess of 4-aminobutyric acid (B) or 6-aminohexanoic acid (H) using N,N-dimethyl formamide (DMF) as solvent. The synthesized compounds were used as curing agents to investigate the effect of structure on the curing and thermal behaviour of diglycidyl ether of bisphenol-A (DGEBA). Structural characterization of DIDAS was done by using FTIR, ¹H-NMR, ¹³C-NMR spectroscopy and elemental analysis. Curing behaviour of DGEBA in the presence of aromatic DIDAS was investigated by differential scanning calorimetry (DSC). The peak exotherm temperature (T _P) was low in the case of DIDAS synthesized from ODA and high in the case of DIDAS synthesized from NTDA. Thermal stability of the isothermally cured DGEBA with DIDAS was investigated using dynamic thermogravimetry in nitrogen atmosphere. The char yield was highest for resin cured with DIDAS containing NTDA.     

The electrochemistry of particles, droplets, and vesicles �C the present situation and future tasks

Presently, a plethora of techniques is available to study the electrochemical properties of solid inorganic and organic micro- and nano-particles immobilized on electrode surfaces, provided that they possess a faradaic electroactivity. Similarily, immobilized droplets of liquids and solutions, which are immiscible with the electrolyte solution, give access to the three-phase electrochemistry of redox centers in the droplets, allowing determinations of free energies of ion transfer between the immiscible liquid phases. Possible and necessary future activities in the field of immobilized particles and droplets will be discussed here. The electrochemistry of suspended micro- and nano-particles possessing faradaic electroactivity is much more complex and needs special attention in future research. Finally, the electrochemistry of liposomes and biological vesicles, which do not possess faradaic activity, but the ability to produce capacitive signals upon attachment to electrodes, will be discussed focusing on possible future developments.     

Studies on the Adsorption and Dissociation of Methane and Carbon Dioxide on Nickel Catalysts

The adsorption and dissociation of methane and carbon dioxide for reforming on nickel catalysts were extensively investigated by TPSR, TPD, XPS and pulse reaction methods. These studies showed that the decomposition of methane results in the formation of at least three kinds of surface carbon species on supported nickel catalysts. Carbidic Cα, carbonaceous Cβ and carbidic clusters C-γ surface carbon species formed by the decomposition of methane demonstrated different surface mobility, thermal stability and reactivity. Carbidic Cα is a very active and important intermediate in carbon dioxide reforming with methane, and the carbidic clusters Cγ species might be the precursor of surface carbon deposition. The partially dehydrogenated Cβ species can react with H2 or CO2 to form CH4 or CO. On the other hand, it was proven that CO2 can be weakly adsorbed on supported nickel catalysts, and only one kind of CO2 adsorption state is formed. The interaction mechanism between the species dissociated from CH4     

Studies of the atomization mechanism in a graphite furnace—I. The contents of the gaseous impurities in the furnace and their variations

Using theoretical calculations of the partial pressures of gaseous impurities in the atmosphere in a GFA as a basis, the authors arrived at conclusions which are at variance with those of L'vov and frech and their co-workers. Accordingly, the partial pressure of free oxygen (p_o) in a GFA originates predominantly from the thermal decomposition of the oxides of the analyte and impurities in the matrix during atomization when the temperature is higher than 1000°C; then, p_o depends on the nature of the sample. The total amount of oxygen in a GFA depends on the initial amount of it in the argon gas and the amount released from the sample when the temperature is lower than 1000°C.The variation of the partial pressure of CO is for the first time characterized as follows: the content of CO, which is mainly dependent on the sample and the total amounts of gaseous impurities in the argon purge gas, does not vary markedly with the temperature and other factors during the whole process of atomization. The gaseous impurities exist mainly in the form of CO.     

Quantum Chemistry Studies on the Difference of Structures and Electronic Properties of Polyacene,Polypyridinopyridine and Paracyanogen

IntroductionThestudiesonconductivepo1ymershavebeenofmuchinterestsbothinex-perimentalworkandtheorysincetheresultsonconductivityofdopedpolyacety-lenewerereported.Itwasreportedthatthehighestconductivityofdopedpoly-acetylenereachedupto1O5s/cmandjustfellintherangeofmetalconduction[1].Somepeoplehaveputforwardone-dimension(1D)graphitematerialfamilytobeconsistedofcondensedaromaticrings.Therearetwbkindsofimportantmolecularskeletonsforms,oneisanextended.versionfrompolyacene.Thepolyacenecanbeobtaintedb…     

A new type of polarographic catalytic wave of organic compound——Studies on the polarographic catalytic wave of medroprogesterone acetate in the presence of KIO_3

The polarographic behavior and catalytic wave mechanism of medroprogesterone acetate (MPA) were studied in both aqueous and DMF media. In 0.2 mol/L acetic acid-sodium acetate (pH 5.0) buffer solution, the C=C bond of MPA first undergoes le, lH~ reduction to form protonated free radical HMPA(?), the further reduction of HMPA(?) in le, 1H~ process is simultaneous with the dimerization reaction between HMPA(?) and neutral molecular MPA. In DMF media containing 0.1 mol/L tetrabutylammonium tetrafluoborate (TBA·BF_4), the C=C bond of MPA shows two le, 1H~ reduction waves, which are ascribed to the reduction of MPA and free radical MPA, respectively. Here, no dimerization reaction occurs. These processes produce the reduction wave of MPA. In the presence of oxidant KIO_3, a polarographic catalytic wave of MPA is observable due to a chemical reaction between HMPA(?) or MPA(?) and KIO_3 as well as its intermediate species to regenerate MPA. The catalytic wave, which is caused by the reduction of organic com     

Studies on the Model Synthesis of the Brassinolide and Dolicholide Side Chains

A stereoselective synthesis of brassinolide and dolicholide, which involves construction of the side chain enantiomers by a highly stereoselective aldol reaction of aldehyde 5 with the anion of a-silyloxy ketone 6 is described.     

Studies on the Performance and Structure of Supported Catalysts for the Partial

The catalytic properties of several supported metal catalysts on different carriers were studied in the partial oxidation of methane (POM) to syngas. In our experiment, supported noble metal catalysts exhibited better performance than the other supported transition metal catalysts. The catalyst performances were significantly influenced by the d-electron configuration of the active metal components and the dispersion of active metal components on the support. A catalyst with a moderate number of unpaired electrons in the d-orbital of the active metal support without obvious acidity or redox activity (e.g. MgO) was suitable for POM performance. The Rh/SiO2 catalyst was the best in the POM reaction, among those investigated. Reaction conditions apparently also affected the POM performance of the catalyst. The conversion of methane and the selectivity for CO increased with the reaction temperature, and a high CH4/O2 ratio was not beneficial for POM performance.     

Studies on the synthesis of chiral nonracemic 3,4-disubstituted azepanes,a formal synthesis of (+)- and (−)-balanol

Sugar lactones were converted to 3,4-disubstituted azepanes and caprolactam derivatives by selective deoxygenation, functionalization and reductive cyclization. The cyclization proved troublesome with 6-azidolactols but led to good results with the corresponding lactones. A formal synthesis of (+)- and (−)-balanol is reported.