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1.
On the basis of chemical transformations and with the aid of physicochemical results, the structure of glycoside I isolated from the roots of the plantMedicago sativa has been established as hederagin 3-O-[O-α-L-arabinopyranosyl-(1 → 2)-β-D-glucopyranosyl-(1 → 2)-α-L-arabinopyranoside] 28-O-β-D-glucopyranoside. Compound (I), C52H84O22, mp 210–212°C, [α] D 21 +38.4° (c 1.48; methanol). Acid hydrolysis of (I) led to hederogenin (II) — C30H48O4, mp 326–330°C, [α] D 23 +84.2° (c 0.19; pyridine. The Hakomorimethylation of glycoside (I) yielded the permethylate (IV) — C65H11O22 [α] D 23 +41.6° (c 1.79; methanol). The GLC analysis of the products of the methanolysis of compound (IV) showed the presence of 3,4,6-tri-O-methyl-D-glucopyranose, 2,3,4,6-tetra-O-methyl-D-glucopyranose, 3,4-di-O-methyl-L-O-arabinopyranose, and 2,3,4-tri-o-methyl-L-arabinopyranose. The alkaline hydrolysis of glycoside I gave compound (III) with mp 230–233°C, [α] D 21 +35.2° (c 0.21; methanol), which was identified as medicoside C. Details of the PMR spectrum are given for compound (IV) and of the IR spectrum for compound (I).  相似文献   

2.
The new phytoecdysteroid 5α-ecdysterone 22-O-benzoate (I), C34H48O3, mp 262–274°C (methanol-water) [α] D 20 +45.8° (methanol), has been isolated from the epigeal organ ofSilene scarbiofolia Kom. The alkaline hydrolysis of (I) led to 5α-ecdysterone (II) and benzoic acid. The isomerization of ecdysterone (0.6% KHCO3 in CH3OH) has yielded (II). Details of the IR, mass, and NMR spectra of compound (I) are given.  相似文献   

3.
A new steroid glycoside — alliospiroside B (I) — has been isolated from the collective fruit ofAllium cepa L. On the basis of chemical transformations and with the aid of physicochemical measurements it has been established that compound (I) has the structure of (25S)spirost-5-ene-1β,3β-diol 1-O-[O-α-L-rhamnopyranosyl-(1 → 2)-β-D-galactopyranoside. Compound (I) C39H62O3, mp 200–202°C (from ethanol). [α] D 20 ?110.9±2° (c 1.01; pyridine) was obtained by extracting the collective fruit ofA. cepa with ethanol folowed by the column chromatographic separation of the combined glycosides on silica gel. The acid hydrolysis of (I) gave (25S)-ruscogenin (II), C27H42O4, mp 189–191°C, [α] D 23 ?104.1±2° (c 0.98; pyridine). The1H and13C NMR spectra are given for both compounds and the IR spectrum for compound (I).  相似文献   

4.
From a methanolic extract of the epigeal part ofRhinopetalum stenantherum have been isolated β-chaconine (I) and the new glucoalkaloids stenanthine with mp 262–264°C [α]D 46.5°, C45H73NO15 (II), and stenanthidine with mp 269–271°C, [α]D ?47.5°, C39H63NO11 (III). On the basis of the facts that partial hydrolysis of the trioside (II) formed the biosides (I) and (III), and that on the hydrolysis of the latter the monoside γ-chaconine was found, it may be assumed that stenanthine has the structure of solanidine 3-0-{[0-β-D-glucosyl-(1 → 6)]-[0-α-L-rhamnosyl-(1 → 4)]-D-glucoside}, and stenanthidine that of solanidine 3-0-[0-β-D-glucosyl-(1 → 6)-D-glucoside].  相似文献   

5.
A phase diagram of the PbF2–SnF2 system has been studied by differential thermal analysis and X-ray powder diffraction. The system forms Pb1–хSnхF2 (х ≤ 0.33) solid solution and three compounds. Pb2SnF6 decomposes in solid state by a peritectoid reaction at 350°С; Pb3Sn2F10 and PbSnF4 melt by peritectic reactions at 565 and 380°С, respectively. The eutectic coordinates are 180°С, 90 mol % SnF2.  相似文献   

6.
Thermosensitive star-shaped poly(2-isopropyl-2-oxazoline) is studied via light scattering in D2O solutions in a ten-fold concentration range at the temperatures from 21 to 60°С. The data are compared to the results of investigations on this polymer in Н2O at close concentration values. A qualitative similarity in behavior of the polymer in the compared solvents is established; the changes that occur after the change from Н2O to D2O are quantitative. After changing to the deuterated solvent, the initial temperature of phase separation decreases by 0.5–1.0°С. The lower the solution concentration, the greater the width of the phase-separation interval.  相似文献   

7.
A new Tb3+-intercalated layered octosilicate (Tb-Oct) was prepared through protonation, exfoliation and intercalation processing. Photoluminescence of the Tb-Oct silicates dependant of phase transition has been investigated in detail. The emissions attributed to 5D4-7FJ (J = 3, 4, 5, 6) transition of Tb3+were observed from the emission spectra of the as-prepared Tb-Oct silicates. After the as-prepared Tb-Oct silicates thermal treatment at 200 °C, all diffraction peaks disappeared, suggesting the collapse of layered structure. With the increase in the annealing temperature from 200 to 1000 °C, no diffraction peaks appeared in all the annealed samples. Photoluminescence spectra show that the green emission ascribed to 5D4-7F5 transition of Tb3+ markedly increased as the sample was annealed at 800 °C. However, this green emission disappeared while the sample was annealed at 400, 600, and 1000 °C, which may relate to actual surroundings of Tb3+ ions. That is, the amorphous phase formed at 800 °C is more favorable for the green emission of Tb3+.  相似文献   

8.
CO adsorption on (0.5–15)%CoO/ZrО2 catalysts has been investigated by temperature-programmed desorption and IR spectroscopy. At 20°С, carbon monoxide forms carbonyl and monodentate carbonate complexes on Co m 2+ O n 2- clusters located on the surface of crystallites of tetragonal ZrO2. With an increasing CoO content of the clusters, the amount of these complexes increases and the temperature of carbonate decomposition, accompanied by CO2 desorption, decreases from 400 to 304°С. On the 5%CoO/ZrО2 sample, the carbonyls formed on the Со2+ and Со+ cations and Со0 atoms decompose at 20, 90, and 200–220°С, respectively, releasing CO. At 20°С, they are oxidized by oxygen to monodentate carbonates, which decompose at 180°С. Adsorbed oxygen decreases the temperature of their decomposition on oxidation sites by ~40°C, and the sample remains in an oxidized state ensuring the possibility of subsequent CO adsorption and oxidation. The rate of the oxidation of 5%CoO/ZrО2 containing adsorbed CO by oxygen is higher than the rate of the oxidation of the same sample reduced by carbon monoxide, because the latter reaction is an activated one. In view of the properties of the complexes, it can be concluded that the carbonates decomposing at 180°С are involved in CO oxidation by oxygen from the gas phase in the presence of hydrogen, a process occurring at 50–200°С. The rate-limiting step of this process the decomposition of the carbonates, which is characterized by an activation energy of 77–94 kJ/mol.  相似文献   

9.
The phase behaviour of the discotic mesogen 2,3,6,7,10,11-hexahexylthiotriphenylene (HHTT) was investigated under hydrostatic pressures up to 500 MPa using high pressure optical and DTA measurements. The known enantiotropic phase transitions of HHTT, i.e. crystal (Cr)-helical phase (H), H-hexagonal columnar phase (Colh) and Colh-isotropic liquid (I) were observed up to 32 MPa. Application of hydrostatic pressures above 32 MPa results in the H and Colh phases becoming monotropic, depending upon the applied pressure. The H phase was observed as a monotropic phase in the pressure region between 32 and about 180 MPa. Thus, the I →Colh →H →Cr transition sequence appeared only on cooling under these pressures, while the Cr →Colh →I transition occurred on heating. Further increases in pressure above a second limiting value leads to the Colh phase becoming monotropic. Thus the I →Colh →Cr transition sequence appeared on cooling, while the Cr →I transition was observed on heating. The T vs. P phase diagram based on the data obtained in the heating mode contains two triple points; one is estimated as 40 MPa, 77.2°C for the Cr-H-Colh triple point and the other is extrapolated as 285 MPa, 118.3°C for the Cr-Colh-I triple point. These triple points define the upper limits for the appearance of the stable H and Colh phases, respectively.  相似文献   

10.
《Solid State Sciences》2012,14(7):971-981
α, β and γ-Ga2O3 have been successfully obtained in an easily scalable synthesis using aqueous solution of gallium nitrate and sodium carbonate as starting materials without any surfactant and additive. α and β-Ga2O3 were obtained by calcination at 350 and 700 °С, respectively, of α-GaOOH, prepared by controlled precipitation at constant pH 6 and T = 55 °С, with 24 h of aging. Aging was necessary to fully convert the initially preciptated gel into a well-crystalline and phase-pure material. γ-Ga2O3 was obtained after calcination at 500 °С of gallia gel, synthesized at constant pH 4 and T = 25 °С, without aging. These three polymorphs have a for gallia relatively high surface area: 55 m2/g (α-Ga2O3), 23 m2/g (β-Ga2O3) and 116 m2/g (γ-Ga2O3). The combination of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), nitrogen physisorption and thermogravimetry (TG) was employed to characterize the samples and their formation.  相似文献   

11.
Phase equilibria in the system K,Cа∥SO4,CO3,HCO3–H2O have been studied at 25°С. This system at 25°С involves 7 invariant points, 21 monovariant curves, and 22 divariant fields. The data gained served to plot the first phase diagram (phase complex) of the studied system at 25°С.  相似文献   

12.
The magnetic circular dichroism (MCD) for the three low-energy absorption bands of the Eu(C2H5SO4)3·9H2O crystal has been measured at room temperature. It may be well understood from the MCD as well as from other experimental results that two of these bands, 7F15D0 and 7F05D1, are of magnetic dipole origin. However, the MCD of another band at about 18650 cm?1, 7F15D1, cannot be interpreted as being only one electric dipole in origin, which has been pointed out by several investigations. The present MCD analysis indicates that although this broad band consists of one electric- and two magnetic-dipole transitions, each of which has a sizeable absorption strength, the MCD spectrum originates exclusively from the two magnetic dipole transitions  相似文献   

13.
The phase diagram of an ethylene glycol (EG)–hexamethylphosphorotriamide (HMPT) system is studied over two wide temperature intervals (+25°С…?90°С…+40°С) and (?150°С…+40°С) by means of differential scanning calorimetry using INTERTECH DSC Q100 and METTLER TA4000 DSC instruments (Switzerland) in the DSC30 mode with variable cooling/heating rates. Substantial overcooling of the liquid phase, a glass transition, and different types of interaction are observed in the system. No thermal effects are observed in intermediate range of concentrations during the slow cooling/heating processes, and the system remains liquid until the glass transition. The presence of such a metastable phase is attributed to a sharp rise in the viscosity of the system due to different kinds of interaction between the components. HMPT: 2EG and HMPT: EG compounds with crystallization temperatures of +5 and ?0.5°С, respectively, are observed upon rapid cooling and slow heating. Changes in enthalpy are calculated for all of the observed thermal effects. The distinction from the phase diagram of H2O–HMFT (literary data) is explained by the difference in the interactions between system components and by the structural differences between EG and H2O.  相似文献   

14.
The heteronuclear complex [Fe4Li2(O)2(Piv)10(H2O)2] (1, Piv is the pivalic acid anion) was obtained by refluxing FeIII pivalates with LiI pivalates in toluene and isolated as the 1?PhCH3 solvate with a toluene molecule. According to X-ray diffraction data, complex 1 contains the {Fe4Li2O2} core. The Mössbauer spectroscopy data indicate that the core comprises para magnetic FeIII ions in the high-spin state located in the symmetric octahedral environment of oxygen atoms. Thermolysis of 1 studied by simultaneous thermal analysis demonstrated thermal stability of the complex up to 225 °С. The main end product of thermolysis at 600 °С is the mixed oxide LiFe5O8.  相似文献   

15.
Octafluorobiphenylene was made by heating 1,2-diiodotetrafluorobenzene in a sealed, evacuated tube with either copper, lead or bismuth. The crystal used for the diffraction studies was grown from hexane. Crystal data: C12F8, Mr = 296.116, monoclinic, A2/a, a = 21.140(2), b = 6.430(6), c = 36.340(3) ÅA, β = 123.76(3)°, U = 4106.73 ÅA3, Z = 16, Dm = 1.884 g cm−3, Dx = 1.907 g cm−3, λ(Cuka) = 1.5418 ÅA, μ = 1.810 mm−1, F(000) = 2304, measurement temperature = 293K, R = 0.059 for 2230 reflections with I > 3σ(I).  相似文献   

16.
The reaction of CuCl2 · 2H2O with pyridine-2,4,6-tricarboxylic acid (H3Pyta) in ethanol and water under hydrothermal synthesis conditions leads to the formation of a trinuclear copper polymer {[Cu3(Pyta3–)2(H2O)8] · 4H2O}n (I) (C16H28N2O24Cu3, Mr = 823.05, ρcalcd = 1.955 g cm–3). The polymer was characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and X-ray single-crystal diffraction (СIF file CCDC no. 1525203). The result showed that I belongs to the monoclinic system, P21/c space group. TGA curve shows that polymer I first removes water molecules, and then the ligand split for polymer I, and the remained residue is CuO. The magnetic measurement reveals the pyridine-2,4,6-tricarboxylic acid as bridge ligand can mediate the antiferromagnetic coupling interaction between magnetic centers.  相似文献   

17.
《Chemical physics letters》1985,116(4):295-301
The value of the proton diffusion coefficient DH+ in ice was extracted from the diffusion-controlled rate kD of the proton recombination reaction RO + H3O+kD ROH + H2O in polycrystalline doped ice. At −10°C, DH+ was estimated to lie between 3.5×10−6 and 1.3×10−5 cm2 s−1, well below the corresponding value of (4.1 ± 0.1)×10−5 cm2 s−1 found in supercooled water.  相似文献   

18.
The molecular structures of the title compounds have been determined by gas phase electron diffraction methods. The SiMn and GeMn bond lengths are 240.7 ? 0.5 and 248.7 ? 0.2 pm respectively and the CMnC angles in the silyl and germyl cases are 94.5 ± 2° and 97 ± 2° respectively. Comparisons are made with the reported structure of CH3Mn(CO)5 and HeI photoelectron spectra of these compounds in an attempt to determine the extent of d → d π-bonding in the SiMn or GeMn bonds.  相似文献   

19.
By repeated chromatography on Polikhrom-1, silica gel, and Florisil, ethanolic extracts of two species of starfish,Culcita novaeguineae andLinckia guildingi, have yielded the new steroid glycoside culcitoside C1 (I): 5α-cholestan-3β,4β,6α,8,15β,24ξ-hexaol 24-O-[2,4-di-O-methyl-β-D-xylopyranosyl-(1→2)-α-L-arabinofuranoside], C39H68O14, mp 245–248°C, [α]D -35.8°, c 0.6; methanol). Its structure was shown by the results of acid hydrolysis, acetylation and methylation, and1H and13C NMR spectroscopy.  相似文献   

20.
The reaction of π-cyclopentadienyl-π-1,5-cyclooctadienerhodium(I) and diphenylacetylene gives hexaphenylbenzene as the principal product with a low yield of π-cyclopentadienyl-π-tetraphenylcyclobutadienerhodium(I). The crystal structure of π-cyclopentadienyl-π-tetraphenylcyclobutadienerhodium(I) was determined by X-ray diffraction techniques using diffractometer data. The crystals are monoclinic with unit cell dimensions of a=13.416(3), b=19.534(6), c=13.411(2) Å and β=135.01 (1)°. The space group is P21/c and, with four molecules per unit cell, no molecular symmetry is required (Dm=1.40 g/cm3 and Dc=1.411 g/cm3). The structure was solved by the heavy atom method and refined by least-squares methods to a final R of 0.043 for the 3675 observed reflections used in the analysis. The rhodium atom is coordinated to both the cyclopentadienyl group (Rh-ring distance is 1.868 Å) and the tetraphenylcyclobutadiene group (Rh-ring distance is 1.828 Å). The phenyl groups are twisted relative to the C4 ring and bent away from the rhodium atom.  相似文献   

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