Thermal transformations in systems based on zeolites Y,X, and A containing zinc and sodium nitrates

Thermal transformations in systems formed by interaction of Zn and Na nitrates with Y, X, and A zeolites were studied by TG—DTA technique. Temperature regions of existence of adsorbed water, water of crystallization, and decomposition of NO₃ ^– anion were determined. These intervals depend on the composition, structure, method of preparation, and pre-treatment conditions of zeolite systems. The extent of NO₃ ^– decomposition depends not only on the zinc and sodium content but also on the presence of ammonia involved in NO₃ ^– reduction. The zeolite matrix strongly stabilizes the occluded NO₃ ^– anions. A portion of zinc oxide formed by zinc nitrate decomposition is probably localized inside the zeolite cavities as the [Zn—O—(ZnO) _n —Zn]²⁺ particles. The latter compensate charges of the isolated [AlO₄]^– tetrahedra.     

The first mu3-oxalato-bridged copper complex with tridentate Schiff base ligand N-ethyl-N'-salicylidene-1,2-diaminoethane: synthesis,structure, and magnetic properties

The first mu(3)-oxalato-bridged copper(II) complex, [[Cu(3)(L)(3)(mu(3)-C(2)O(4))][Cu(L)(H(2)O)](ClO(4))(2)] x 0.5(H(2)O) x 0.5(CH(3)OH), where HL = N-ethyl-N'-salicylidene-1,2-diaminoethane, has been synthesized and characterized by variable-temperature magnetic susceptibility measurement. The complex exhibits ferromagnetic coupling between the oxalato-bridged copper atoms and antiferromagnetic coupling between the oxygen-bridged copper atoms.     

Preconcentration of copper with multi-walled carbon nanotubes pretreated by potassium permanganate cartridge for solid phase extraction prior to flame atomic absorption spectrometry

A procedure for the preconcentration of copper was described in this paper using multi-walled carbon nanotubes (MWCNTs) oxidized by potassium permanganate as the adsorbent for the enrichment of trace copper in water samples. Important parameters, such as the sample pH, the concentration and volume of eluent, sample flow rate and volume, and interference of coexisting ions, were investigated. The obtained results indicated that proposed method possessed an excellent analytical performance. The linear range, the detection limit, and precison (RSD) were 1-100 ng/mL (R2 = 0.9993), 0.32 ng/mL and 2.88%, respectively. The results showed that copper could be adsorbed quantitatively on the pretreated MWCNTs with potassium permanganate, and proposed method was very useful in the monitoring of copper in the environment.     

5α,11-二羟基-2-氧代桉烷-3-烯的全合成

5α，11-二羟基-2-氧代桉烷-3-(5α-Hydroxy—isopterocarpolone，1)是由贾忠建等于1996年从中药南牡蒿中首次分离得到的一种桉烷型倍半萜类天然产物．桉烷型倍半萜类化合物广泛分布于天然植物中，具有较好的昆虫拒食、抑制细胞繁殖和植物生长调节等多种生理活性．天然产物1的合成研究尚未见报道．     

TRITERPENE GLYCOSIDES FROM Tetrapanax papyriferum. III. MINOR MONODESMOSIDE GLYCOSIDES FROM STEM BARK

Minor monodesmoside triterpene glycosides St-A, St-B, St-C ₁ , St-D ₁ , St-C ₂ , and St-D ₂ were isolated from stem bark ofTetrapanax papyriferumC. Koch (Araliaceae). The structures of oleanolic and echinocystic acid 3-O--L-arabinopyranosides, oleanolic and echinocystic acid 3-O--D-glucopyranosyl-(13)-O--L-arabinopyranosides, and oleanolic and echinocystic acid 3-O--D-galactopyranosyl-(12)-O--L-arabinopyranosides, respectively, were proposed. Glycosides St-C ₂ , St-D ₁ , and St-D ₂ are new triterpene glycosides. The structures of the isolated compounds were established using chemical methods and NMR spectroscopy.     

Reactions of 5,6,7,8-tetrafluoro-4-hydroxycoumarin derivatives with benzylamine and aniline

5,6,7,8-Tetrafluoro-4-hydroxycoumarin reacted with benzylamine under mild conditions to give a stable salt, while its refluxing with aniline or benzylamine in xylene afforded 5,6,7,8-tetrafluoro-4-phenyl(benzyl)aminocoumarins. Reactions of 3-acetyl(acetimidoyl)-5,6,7,8-tetrafluoro-4-hydroxycoumarins with benzylamine followed different pathways, depending on the solvent. Condensation at the acyl substituent can be accompanied by replacement of the F atom in position 7. 3-Acetylcoumarin formed a salt, while 3-acetimidoylcoumarin yielded a 7-monosubstituted product. 3-Acetyl(acetimidoyl)-5,6,7,8-tetrafluoro-4-hydroxycoumarins reacted with aniline to give only 5,6,7,8-tetrafluoro-4-hydroxy-3-(N-phenylacetimidoyl)coumarin. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1170–1174, July, 2006.     

Interaction of Nitromethane with Modified Paramagnetic Defects on a Thermochemically Activated Silica Surface

It was found that the interaction of the modified paramagnetic defects SiO(CH₂) _n H₂ (n = 0.1) with nitromethane on a thermochemically activated silica surface at 300 K results in the formation of the following nitroxyl radicals: SiO(CH₂) _n CH₂ON( )CH₃ and SiO(CH₂) _n CH₂N( )CH₃. It was suggested that these radicals are the products of two different reactions of the modified paramagnetic defects: the first results from a reaction with free nitromethane; the second, from a reaction with nitromethane bound as complexes with diamagnetic surface defects.     

Synthesis of methyl derivatives of uronic acids. I. Synthesis of methyl (methylα-D-galactopyranosid)uronate and its 2-, 3-, and 4-O-methyl ethers

Alternative unidirectional methods for synthesizing methyl (methyl α-D-galactopyranosid)uronate and its mono-O-methyl ethers by the oxidation (with CrO₃-H₂SO₄-acetone) of the corresponding methyl O-benzyl-O-methyl-α-D-galactopyranosides having unsubstituted 6-OH groups to the corresponding methyl O-benzyl-O-methyl-α-D-galactouronic acids followed by esterification with CH₂N₂ and the catalytic hydrogenolysis of the benzyl groups are proposed.     

Solution Stoichiometry Control for Pure LiLaMo2O8Phases in Sol-Gel Preparation

The hydrolysis of solutions, containing either LiMo₂O₄(OPr ⁱ )₅( ⁱ PrOH) and “La(OPr ⁱ )₃” or LiOPr ⁱ and La₂Mo₄O₈(OPr ⁱ )₁₄ in 1∶1 ratio, in toluene or ⁱ PrOH, by water solutions in isopropanol, leads to formation of monolythic gels. The latter can be converted by drying and heat treatment at 600°C into a fine powder of pure α-LiLaMo₂O₈ phase, which is transformed into β-LiLaMo₂O₈ powder by annealing at 800°C. The sintering of the pellets pressed under 4 bar pressure of α-LiLaMo₂O₈ powder at 800°C for 2 h converts them into pieces of β-LiLaMo₂O₈ transparent ceramics, thus providing a route to LiLnMo₂O₈ laser waveguide materials.     

Approximate expressions of determining the double layer energy and force of interaction between two charged colloidal spheres

The approximate expressions have been obtained to calculate the electrical double layer energy and force between two spherical colloidal particles based on the improved Derjaguin approximation. Results for identical spheres interacting under constant surface potential, constant surface charge are given. Comparison of present results with numerical results calculated by Carnie and Chan is made. The expressions are found to work quite well for the constant surface potential case, and for the constant charge case, we make correction for the expressions. The results given are satisfactory providedkh0.4.