HSAPO-34 分子筛上氧鎓叶立德机理的第一性原理研究

 采用基于周期性边界条件的密度泛函理论研究了 HSAPO-34 分子筛上甲醇通过氧鎓叶立德机理直接耦合生成乙烯的可能性. 结果表明, 二甲醚和三甲基氧鎓离子在 HSAPO-34 分子筛上的生成能垒分别为 1.68 和 0.93 eV, 中间体氧鎓叶立德不能稳定存在, 同时表明 C–C 键通过协同反应形成的能垒均超过 3.0 eV. 因此, 甲醇制烯烃催化过程不可能遵循氧鎓叶立德机理.     

A Novel Rearrangement in the Series of GEM-Bisphos-Phonic Acids

Abstract

Some bisphosphonic acids containing basic side chain sub-stituents are compounds of pharmaceutical interest which are undergoing clinical investigation as agents for the treatment of various bone diseases. 3-Amino-propane-l-hydroxy-1,l-bisphosphonic acid (pamidronic acid, APD) is a well known member of this series (1). When APD was subjected to trimethylsilylation and subsequent distillation at low pressure, a novel rearrangement was observed:     

Synthesis of new pyrido[2,3-d]pyrimidine derivatives by three-component condensation of 5-acetyl-4-aminopyrimidines, cyclohexane-1,3-diones, and orthocarboxylic acid esters

A three-component condensation of 5-acetyl-4-aminopyrimidine derivatives with dimedone (or cyclohexane-1,3-dione) and triethyl orthoacetate (or triethyl orthopropionate) gave derivatives of 7-(1,3-dioxocyclohex-2-ylidene)-7,8-dihydropyrido[2,3-d]pyrimidine. These heterocyclic compounds containing the enamino ketone fragment can form boron chelates under the action of butoxy(diphenyl)borane. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2006–2011, November, 2006.     

环境样品中生物可利用态镉的反相离子对-HPLC-荧光检测

镉是一种有毒的重金属元素 ,是生态环境中最常见和最主要的污染元素之一 [1] .目前 ,用于镉的测定方法主要有原子吸收法 [2 ]、ICP- MS法 [3]和荧光分光光度法 [4 ] ,但这些方法由于灵敏度或者选择性的限制以及来自基体的严重干扰等问题 ,常常在实际样品测定中遇到困难 .高效液相色谱及其联用技术的发展使复杂样品中痕量元素的测定得以实现 [5～ 7] .本文将长链的阳离子表面活性剂十六烷基三甲基溴化铵 ( HTMAB)作为离子对试剂 ,8-羟基喹啉 - 5 -磺酸 ( HQS)作为在线配位及荧光衍生试剂 ,建立了镉的离子对色谱检测方法 ,并应用于土壤…     

多取代芳香类聚酰胺的合成

芳香聚酰胺具有优异的热稳定性,但在溶剂中的溶解性能较差。人们发现在聚酰胺中的苯环上引进甲基取代基是改善聚合物溶解性能的一种有效的途径,Takatsuka等曾合成了一系列一取代和二取代甲基的芳香聚酰胺,聚合物的溶解性有较大的改善。但尚未见关于三甲基取代聚合物的合成报道。     

First example of regioselective nucleophilic 1,6-addition of trimethyl(trifluoromethyl)silane to 4H-chromene derivatives

Condensation of 2-trifluoromethylchromone with diethyl malonate, ethyl cyanoacetate, and Meldrum’s acid gave the corresponding methylidene derivatives of 2-trifluoromethyl-4H-chromene. Nucleophilic 1,6-addition of an excess of Me₃SiCF₃ in the presence of Me₄NF to those obtained from the former two compounds afforded 4-substituted 2,2-bis(trifluoromethyl)-2H-chromenes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1628–1630, September, 2006.     

Hydrocarbon chain packing in the micellar core of surfactants studied by 1H NMR relaxation

 ¹H NMR spin–lattice and spin–spin relaxation of different types (cationic cetyltrimethyl ammonium bromide, anionic sodium dodecyl sulfonate and nonionic Triton X-100) of surfactants in water solution were studied. Simulation of the decay curves of proton relaxation shows that the spin lattice relaxation of all the samples exhibits exponentially, while the spin–spin relaxation for several protons on the hydrophobic chains forming the micellar core is bi-exponential. The fast relaxing component is attributed to the part of the segments of the hydrophobic chain, situated near or on the surface of the micellar core, while the slower relaxing component is attributed to the rest part staying in the interior. The latter exchanges with the former in equilibrium. Thus, a part of each certain segment of the hydrophobic chain has an opportunity to stay in the surface layer of the micellar core and spend some time on the interface experiencing hydrophilic environment. Generally, the protons on the methylene carbon of the hydrophobic chain nearest to the polar head have more chance to spend time in the hydrophilic environment. However, it seems to be dependent on the chemical structure of the surfactant molecule. Large size of the polar group of CTAB shows steric hindrance on the packing of the hydrophobic chain. Quantitative results are given. The fact, that the fraction of slow relaxing protons on the hydrophilic ethylene oxide long chain of Triton X-100 dominates over that of fast relaxing protons, and that their T ₂ values are larger than those of the protons on the hydrocarbon chain in the interior of the micellar core, suggests that the ethylene oxide chain does not participate in the formation of the micellar core. Received: 10 March 1998 Accepted: 19 June 1998     

Study on Determination of Trace Copper by Spectrophotometry after Flotation Separation Using Microcrystalline Adsorption System

The paper presents a novel method for the flotation separation of Cu²⁺ using microcrystalline adsorption system prior to the determination by spectrophotometry. The effects of different parameters, such as the dosages of NH₄SCN and octadecyl trimethyl ammonium bromide (OTMAB), various salts on the flotation yield of Cu2+ have been investigated to select the optimum experimental conditions. The possible flotation separation mechanism of Cu²⁺ was discussed. The results showed that under the optimum conditions, octadecyl trimethyl ammonium bromide cation (OTMAB⁺) reacted with SCN^‐ to produce the microcrystalline matter (Ms‐M) of (OTMAB⁺·SCN^‐), the water‐insoluble ternary association complex of [Cu(SCN)₄] (OTMAB)₂ which produced by Cu²⁺ and SCN^‐, OTMAB⁺ was quantificationally adsorbed on the surface of Ms‐M of (OTMAB²⁺·SCN^‐) and was floated above water phase, the liquid‐solid phases were formed with clear interface. In this condition, K⁺, Na⁺, Ca²⁺, Mg²⁺, Al³⁺, Fe²⁺, Mn²⁺, Ni²⁺, Cd²⁺ and Co²⁺ could not be floated. Therefore, Cu²⁺ was separated completely from the above metal ions. A new method of determination of trace copper by flotation separation was established. The proposed method has been successfully applied to the determination of Cu²⁺ in plating waster water, and the results agreed well with AAS method. The recoveries were 93.3%～107.8%, and the RSD was 1.9%～2.1%.     

Introduction of Adjacent Oxygen‐Functionalities in Dimethyl Heptalenedicarboxylates

The bromination of dimethyl 8‐methoxy‐1,6,10‐trimethylheptalene‐4,5‐dicarboxylate ( 6 ; Scheme 2) with N‐bromosuccinimide (NBS) in N,N‐dimethylformamide (DMF) leads in acceptable yields to the corresponding 9‐bromoheptalenedicarboxylate 10 (Table 1). Ether cleavage of 6 with chlorotrimethylsilane (Me₃SiCl)/NaI results in the formation of oxoheptalenedicarboxylate 13 in good yield (Scheme 4). The latter can be acetyloxylated to the (acetyloxy)oxoheptalenedicarboxylate 14 with Pb(OAc)₄ in benzene (Scheme 5). Oxo derivative 14 , in turn, can be selectively O‐methylated with dimethyl sulfate (DMS) in acetone to the (acetyloxy)methoxyheptalenedicarboxylates 15 and 15′ (Scheme 6). The AcO group of the latter can be transformed into a benzyl or methyl ether group by treatment with MeONa in DMF, followed by the addition of benzyl bromide or methyl iodide (cf. Scheme 9). Reduction of the ester groups of dimethyl 7,8‐dimethoxy‐5,6,10‐trimethylheptalene‐1,2‐dicarboxylate ( 25′ ) with diisobutylaluminium hydride (DIBAH) in tetrahydrofuran (THF) leads to the formation of the corresponding dimethanol 26′ , which can be cyclized oxidatively (IBX, dimethyl sulfoxide) to 8,9‐dimethoxy‐6,7,11‐trimethylheptaleno[1,2‐c]furan ( 27 ; Scheme 11).     

Preconcentration/Separation of Some Metal Ions Using Sodium Dodecyl Sulfate Coated Alumina Modified with Bis(5‐bromo‐2‐hydroxy‐benzaldehyde)‐2‐methyl‐1,5‐pentane Diimine (BBHBPDI) Prior to Their Flame‐AAS Determination

Preconcentration/separation of Co(II), Fe(III), Pb(II), Cr(III), Cu(II) and Cd(II) ions using bis(5‐bromo‐2‐hydroxy‐benzaldehyde)‐2‐methyl‐1,5‐pentane diimine (BBHBPDI) on SDS coated alumina has been reported. The influences of the analytical parameters including pH, ligand and SDS amount, type and concentration of eluent and sample volume on metal ions recoveries were investigated. At optimum values of all variables the relative standard deviation are between 2.5–2.7 and preconcentration factor was 375, while recoveries for all understudy metal ions are higher than 95%, determination limits are between 1.5–2.7. The method has been successfully applied to determination of Co(II), Fe(III), Pb(II), Cr(III), Cu(II) and Cd(II) ions content in some real samples.