Phase transition in LAMOX type compounds

La₂Mo₂O₉ (LMO) was synthesized at lower temperature 973 K (LT-phase) by ceramic route. Differential thermal analysis (DTA) scan of LT-phase of LMO showed α→β transition at 843 K during heating and β→α conversion via a metastable γ-phase during cooling. This was also confirmed by thermo-dilatometry and impedance spectroscopy. La₂Mo_1.95V_0.05O_9-δ (LMVO), La_1.96Sr_0.04Mo₂O_9-δ (LSMO) and La_1.96Sr_0.04Mo_1.95V_0.05O_9-δ (LSMVO) were prepared in a similar way. These compounds exhibited α→β transition on heating with shift in transition temperature, but the existence of γ-phase during cooling disappeared. Substitution increased the ionic conductivity of α-phase and reduced that of β-phase.     

Triterpene glycosides of Hedera taurica VI. Structures of hederosides G,H1, H2, and I from the berries of Crimean ivy

We have isolated from Crimean ivy berries in addition previously known triterpene glycosides — 3-O-α-L-arabinopyranosyl-28-O-[O-α-L-rhamnopyranosyl-(1 → 4)-O-β-D-glycopyranosyl-(1 → 6)-β-D-glucopyranosyl]hederagenin, 3-O-[O-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl]-28-O-[O-α-L-rhamnopyranosyl-(1 → 4)-O-β-D-glucopyranosyl-(1 → 6)-β-D-glycopyranosyl]hederagenin, the new triterpene glycosides hederoside H₂-3-O-[O-β-D-glycopyranosyl-(1 → 2)-β-D-glycopyranosyl-(1 → 2)-β-D-glucopyranosyl]-28-O-[O-β-D-glucopyranosyl-(1 → 6)-β-D-glucopyranosyl]oleanolic acid- and hederoside I-3-O-[O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosyl]-28-O-[O-β-D-glucopyranosyl-(1 → 6)-β-D-glucopyranosyl]hederagenin. Details of their¹³C NMR spectra are given. M. V. Frunze Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 779–783, November–December, 1990.     

Kinetic analysis of the α-β HgI2 phase transition

The kinetics of the α-β phase transition of HgI₂ were investigated by isothermal and non-isothermal differential scanning calorimetry. The effective activation energy of the transition, 415±40 kJ mol^-1, was determined applying the methods of Kissinger and Ozawa. The transition kinetics were described by the Johnson-Mehl-Avrami model and the value of the Avrami exponent n was found to range from high values (n>3) at the early stages to lower values at later stages of the transformation, with an average value of 2. This revised version was published online in August 2006 with corrections to the Cover Date.     

XRD and thermal studies of AgI confined in nm-size pores by forming porous silica-AgI composites

To investigate the nm-size dependence of structural and thermal properties for AgI, the formation of composites between AgI and porous silica with controlled pore diameters of 10, 15, 30, and 50 nm was examined. The introduction of AgI within the micropores of the porous silica was performed successfully by a salt-bridge precipitation method with using AgNO₃ and KI aqueous solutions. The AgI formed within the micropores was identified to be β/γ-AgI, independent of the pore size of 10-50 nm, by powder X-ray diffractometry. In differential scanning calorimetry, the composites showed thermal anomaly at around 150°C on heating due to the phase transition from β/γ -AgI to α -AgI as in the case of bulk crystalline AgI (T _trs=147°C). However, the transition temperature from α-AgI to β/γ -AgI on cooling decreased remarkably with the decrease of the pore size from 50 to 10 nm. The result indicates the possibility for AgI particles with diameter less than 10 nm to exist as α -AgI even below 100°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dehydration Reaction of Manganese(II) Oxalate Dihydrate in the Solid State New Method in the Study of Non-isothermal Kinetics

A new method was proposed for determining the most probable mechanism function of a solid phase reaction. According to Coats-Redfern's integral equation E_β→0 was calculated by extrapolating β to zero using a series of TG curves with different heating rates. Similarly, E_α→0 was calculated according to Ozawa's equation. The most probable mechanism function of the solid phase dehydration of manganese(II) oxalate dihydrate was confirmed to be G(α)=(1-α)^1/2 by comparing E_α→0 with E_β→0. This revised version was published online in July 2006 with corrections to the Cover Date.     

Steroid saponins and sapogenins ofAllium IX. The structure of aginoside

From a methanolic extract of the skins of the bulbs ofAllium giganteum Rgl, a new steroid glycoside has been isolated — aginoside, which is (25R)-5α-spirostan-2α, 3β, 6β-triol 3-0-{[0-β-D-xylopyranosyl-(1→3)-]-[0-β-D-glucopyranosyl-(1→2)]-0-β-D-glucopyranosyl-(1→4)-0-β-D-galactopyranoside}.     

New polyhydroxysteroids and steroid glycosides from the far east starfishCeramaster patagonicus

Two new polyhydroxysteroids and five new glycosides were isolated from the starfishCeramaster patagonicus and their structures were elucidated: 5α-cholestane-3β,6α,15β,16β,26-pentol, (22E)-5α-cholest-22-ene-3β,6α,8,15α,24-pentol, (22E)-28-O-[O-(2-O-methyl-β-d-xylopyranosyl)-(1→2)-β-d-galactofuranosyl]-24-hydroxymethyl-5α-cholest-22-ene-3β,4β, 6α,8,15β,16β,28-heptol (ceramasteroside C₁), (22E)-28-O-[O-(2,4-di-O-methyl-β-d-xylopyranosyl)-(1→2)-β-d-galactofuranosyl]-24-hydroxymethyl-5α-cholest-22-ene-3β, 6α,8,15β,16β,28-hexol (ceramasteroside C₂), (22E)-28-O-[O-methyl-β-d-xylopyranosyl)-(1→2)-β-d-galactofuranosyl]-24-hydroxymethyl-5α-cholest-22-ene-3β,6α,8,15β,16β 28-hexol (eramasteroside C₃), (22E)-28-O-[O-(2-O-methyl-β-d-xylopyranosyl)-(1→2)-β-d-galactofuranosyl]-24-methyl-5α-cholest-22-ene-3β,4β,6α,8, 15β, 26-hexol (ceramasteroside C₄), and (22E)-28-O-[O-(2-O-methyl-β-d-xylopyranosyl)-(1→2)-β-d-xylopyranosyl]-5α-cholest-22-ene-3β,6α,8,15β,24-pentol (ceramasteroside C₅)). Three known polyhydroxysteroids (24-methylene-5α-cholestane-3β,6α,8,15β,16β,26-hexol, 5α-cholestane-3β,6α,8,15β,16β,26-hexol, and 5α-cholestane-3β,6β,15α,16β,26-pentol) were also isolated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 190–195, January, 1997.     

Synthesis of aminoethyl glycoside of the oligosaccharide chain of ganglioside Fuc-GM1

2-Aminoethyl glycoside of the hexasaccharide chain of ganglioside Fuc-GM₁ was synthesized by a [3+3] synthetic scheme. At the key step of the synthetic route, glycosylation of the only hydroxyl group at C(4) of the galactose residue in an α-(N-acetylneuraminyl)-(2→3)-β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside derivative with a peracetylated thioglycoside of α-L-fucopyranosyl-(1→2)-β-D-galactopyranosyl-(1→3)-2-trichloroacetamido-2-deoxy-β-D-galactopyranose gave a protected hexasaccharide in high yield. Subsequent removal of the protecting groups gave the target 2-aminoethyl glycoside of the oligosaccharide chain of gan-glioside Fuc-GM₁. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 148–153, January, 2006.     

Synthesis and thermal decomposition of lanthanide hexacyanochromate(iii) complexes,Ln[Cr(CN)6]·nH2O (Ln=La-Lu; n=3, 4)

New solid complex of nitrilotriacetic acid and bismuth trichloride was synthesized by a solid phase reaction of nitrilotriacetic acid and bismuth trichloride at room temperature. The composition of the sample is BiCl₃[N(CH₂COOH)₃]_2.5. The crystal structure of the complex belongs to triclinic system with the lattice parameters: α=0.7849 nm, β=0.9821 nm, χ=2.0021 nm, α=96.50°, β=98.76° and γ=90.49°. The far-infrared spectra show the bonding between the Bi ion and N atom of nitrilotriacetic acid. The thermal analysis also demonstrates the complex formation between the bismuth ion and nitrilotriacetic acid. The gaseous pyrolysis product and the final residue in the thermal decomposition process are determined to check the thermal decomposition reaction. This revised version was published online in August 2006 with corrections to the Cover Date.     

β Phase transformations in the Cu–11mass%Al alloy with Ag additions

In the Cu–Al system, due to the sluggishness of the β ↔ (α + γ₁) eutectoid reaction, the β phase can be retained metastably. During quenching, metastable β alloys undergo a martensitic transformation to a β′ phase at Al low content. The ordering reaction β ↔ β₁ precedes the martensitic transformation. The influence of Ag additions on the reactions containing the β phase in the Cu–11mass%Al alloy was studied using differential scanning calorimetry and in situ X-ray diffractometry. The results indicated that, on cooling, two reactions are occurring in the same temperature range, the β → (α + γ₁) decomposition reaction and the β → β₁ reaction, with different reaction mechanisms (diffusive for the former and ordering for the latter) and, consequently, with different reaction rates. For lower cooling rates, the dominant is the decomposition reaction and for higher cooling rates the ordering reaction prevails. On heating, the (α + γ₁) → β reverse eutectoid reaction occurs with a resulting β phase saturated with α. The increase of Ag concentration retards the β → (α + γ₁) decomposition reaction and the β → β₁ ordering reaction, which occurs in the same temperature range, becomes the predominant process.     

Orbital phase control of the conformations of α- and β-substituted enamines and vinyl ethers

The conformational stabilities of the α- and β-substituted enamines and vinyl ethers were predicted by orbital phase theory and confirmed by ab initio molecular orbital calculations. Cyclic interaction significantly occurs among the nonbonding orbital n _Y for the lone pair on the hetero atom Y (N in the enamines or O in the ethers), the π and π* orbitals of the CC bond, and the σ_C-H or σ*_C-X orbitals on the substituent CH₂X. The cyclic -n _Y-π-σ_C-H-π*- interaction is favored by the orbital phase continuity in the α-substituted molecules, while the cyclic -n _Y-π-σ*_C-X-π*- interaction is favored in the β-substituted molecules. The most stable conformation was then predicted to be synperiplanar or (pseudo)equatorial in the α-substituted molecules and anticlinical or (pseudo)axial in the β-substituted molecules. Received: 8 May 1998 / Accepted: 30 July 1998 / Published online: 16 November 1998     

Thermal change of Alq3, tris(8-hydroxyquinolinato) aluminum(III) studied by TG and XRD-DSC

The thermal change of the tris(8-hydroxyquinolinato)aluminum (Alq₃) is currently investigated by XRD-DSC and TG. The phase transition of Alq₃ from α-phase to γ-phase takes place at 643–669 K. A very sharp peak with the peak temperature at approx. 709 K is ascribed to the melting of the Alq₃. The decomposition of the Alq₃ was observed accompanied with the melting and evaporation at >703K. The effect of the atmospheres on the mass loss procedure was studied by TG. It was found that thermal process of Alq₃ was strongly influenced by the partial pressure of water vapor in the atmosphere instead of oxygen.     

A new furostanol glycoside with fatty acid synthase inhibitory activity from <Emphasis Type="Italic">Ophiopogon japonicusa</Emphasis>

A new furostanol glycoside, named ophiopogonin J (1), was isolated from the fibrous root of Ophiopogon japonicas. The structure of the compound was established as (25R)-26-[(O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosyl)]-20α -hydroxyfurost-5, 22-diene-3-O-α-L-rhamnopyranosyl-(1 → 2)-[β-D-xylopyranosyl(1 → 4)]-β-D-glucopyranoside on the basis of spectroscopic methods, including HR-ESI-MS and 1D and 2D NMR experiments.     

Synthesis and some transformations of γ-(p-fluorophenyl)-γ-(2-furyl)propylamine

Ethyl α-cyano-β-(p-fluorophenyl)-β-(2-furyl)propionate was obtained by the condensation of ethyl α-cyano-β-(2-furyl)acrylate with p-fluorophenylmagnesium bromide. Its deethoxycarbonylation led to β-(p-fluorophenyl)-β-(2-furyl)propionitrile. Reduction of the nitrile with lithium aluminum hydride gave γ-(p-fluorophenyl)-γ-(2-furyl)propylamine. Some transformations of the latter were studied. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 503–509, April, 2006.     

Reinvestigation of low-lying levels of231Th

Low-lying excited levels of²³¹Th fed through α-decay of²³⁵U were investigated by using α-γ and γ-γ coincidence technique. From the analyses for co-relating energy levels and transition intensities, we found that the most favorable transition from 205.3 keV ([631]7/2) level that is fed by the most dominant α transition from²³⁵U is 19.6 keV transition (205.3 keV [631]7/2⁻→185.7 keV [631]5/2⁻). We also found that the transition probability of 109.2 keV, 205.3 keV [631]7/2⁻→96.1 keV [633]9/2⁺, was corrected to be weak. These findings can explain why the 185.7 keV γ-ray is so strongly observed, 0.57 photons/ga, in the γ-spectrum associated with the α-decay of²³⁵U. The decay scheme of²³¹Th levels previously reported has been modified according to the present analysis.     

Kinetics of competitive crystallization of β- and α-modifications in β-nucleated iPP studied by isothermal stepwise crystallization technique

Crystallization kinetics of β-nucleated isotactic polypropylene (β-iPP) under isothermal conditions were investigated by differential scanning calorimetry. iPP was nucleated by a trisamide derivative, namely tris-2,3-dimethyl-hexylamide of trimesic acid (TATA). In the presence of TATA possessing dual nucleating ability, the formation of the α- and β-form occurs simultaneously. An isothermal stepwise crystallization method is suggested in this study, which can separate the crystallization process of β- and α-iPP and consequently their crystallization kinetics can be evaluated separately. The results indicated that the mechanism of crystallization changes in temperature especially in the vicinity of the upper critical temperature of the formation of the β-phase. In addition, it was found that the ratio of the growth rates of β- and α-modification determines the characteristics of crystallization and influences the apparent rate constant of crystallization of both polymorphs.     

A new flavone glycoside from the aerial part of <Emphasis Type="Italic">Peganum nigellastrum</Emphasis>

Chemical investigation of the aerial part of Peganum nigellastrum furnished a new flavone glycoside, and the structure was established by NMR, MS, and DEPT, HSQC, and HMBC as diosmetin 7-O-β-Dglucopyranosyl(1→2)-β-D-glucopyranosyl(1→2)-[α-L-rhamnopyranosyl(1→6)]-β-D-glucopyranoside.     

Triterpene glycosides ofHedera helix I. The structures of glycosides L-1, L-2a,L-2b,L-3, L-4a,L-4b,L-6a,L-6b,L-6c,L-7a,and L7-b from the leaves of common ivy

The leaves of common ivy have yielded 11 triterpene glycosides: the 3-O-α-L-pyranosides of oleanolic acid (1), of echinocystic acid (2), and of hederagenin; the 3-O-[O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside]s of oleanolic acid (4), of echinocystic acid (5), and of hederagenin (6); the O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl ester of hederagenin 3-O-α-L-pyranoside (7); the O-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl ester of hederagenin 3-O-[O-α-L-pyranosyl-(1→2)-α-L-arabinopyranoside] (9); and the O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl esters of oleanolic acid, echinocystic acid, and hederagenin 3-O-[O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside]s (8), (10), and (11), respectively. This is the first time that compounds (1), (2), (5), (7), (9), and (10) have been found in this plant. Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 742–746, November–December, 1994.     

Effect of 4 mass% Ag addition on the thermal behavior of the Cu-9 mass% Al alloy

The effect of 4 mass% Ag addition on the thermal behavior of the Cu-9 mass% Al alloy was studied using differential scanning calorimetry (DSC), optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffractometry (XRD). The results showed that the presence of silver causes (Cu)-α+(α+g1)→ (Cu)-α+β transformation to occur in two stages. In the first one, part of the produced b phase combines with the precipitated Ag to give a silver-rich phase and in the second one the transformation is completed. The formation of this silver-rich phase seems to be enhanced at very low cooling rates. This revised version was published online in August 2006 with corrections to the Cover Date.     

Furostane-Type Steroidal Saponin from <Emphasis Type="Italic">Digitalis ciliata</Emphasis>

A new furostane-type steroidal glycoside and derivative of tigogenin (1) was isolated from aqueous wastes from production of the cardiac drug acetyldigitoxin from leaves of Digitalis ciliata Trautv. (Scrophulariaceae) and characterized. The structure of the glycoside was established using physical constants, chemical transformations, and spectral data as 3-O-β-D-glucopyranosyl-(1→3) [β-D-fucopyranosyl-(1→2)-β-D-glucopyranosyl-(1→4)-β-D-galactopyranosyl-(25R)-5α-furostan-3β,22α,26-triol-26-O-β-D-glucopyranoside.