On Bonding,Structure, and Stability of Ternary Hydrides A2MH2 (A = Li,Na; M = Pd,Pt)

Bonding, structure, and stability of solid A₂MH₂ with A = Li, Na; M = Pd, Pt were investigated with a relativistically corrected density-functional approach, which reliably describes the trends among these four compounds. In order to examine the influence of the ligands (A) and of the crystalline environment, calculations were also made for free A₂MH₂ molecules and MH₂^2– ions. The free MH₂^2– complex is held together by strong bonds between formally closed shell atomic units because of strong M-d,s hybridization. The M–H bonds are further stabilized by the alkali metal ion ligands and by the crystal surrounding. The crystal field expands the H–A distance and enhances the H–A polarity. Relativistic effects contribute to M–H bonding in the solid state. The experimentally determined bond lengths and their trends are in accordance with theory. Due to relativistic and lanthanide effects, the Pt–H bond length becomes nearly as short as the Pd–H one. The small Li ion causes a distortion of the Li₂PtH₂ crystal resulting in an even shorter Pt–H bond length. In the gas-phase, A₂PtH₂ is more stable against dissociation than A₂PdH₂. The stability of the solid compounds is strongly influenced by the cohesive energy of the metal M, and also by the nature of the alkali metal. The evaluated enthalpies of formation favor increasing stability of solid A₂MH₂ against disproportionation into M and AH from Pt to Pd and from Li to Na. This is in agreement with experimental findings. The assignment of the experimental vibrational excitations should be reconsidered.     

The Effects of M2O3 on Stabilizing Monocopper over the Surface of Cu-ZnO-M2O3 Catalysts for Mathanol Synthesis

The effects of M₃O₃ (M = Al, Sc etc.) in Cu-ZnO-M₂O₃ catalysts on methanol synthesis at low pressure were studied with ESR, XPS and TPR spectroscopy. The results of ESR showed that the generation of monovalent cationic defects was because the valence state and electronic charge on the ZnO lattice lost their balance as M³⁺ doped into ZnO. The induced effect by Sc³⁺ is stronger than that by Al³⁺. The results of XPS and TPR indicated that the amount and stabilization of Cu⁺ on the surface of reduced copper-based catalyst and its catalytic activity were affected by the monovalent cationic defects on the surface of ZnO.     

Study on the direct analysis of solid powder biological samples using fluorination assisted electrothermal vaporization inductively coupled plasma atomic emission spectrometry with PTFE slurry modifier

A method has been described for the direct determination of Ti, Cu, Mn, Cr and Cd in solid biological samples without any chemical pretreatment by fluorination assisted electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) with slurry sampling. A polytetrafluorethylene (PTFE) emulsion was used as a fluorinating reagent to promote the vaporization of the analytes from the graphite furnace. The interface between furnace device and ICP torch and the main factors affecting the analytical signal were investigated systematically. The detection limits for the determination of Ti, Cu, Mn, Cr and Cd are 6.3, 4.7, 10, 13 and 278 ng/mL, respectively; the relative standard deviations are in the range of 1.5 (Mn) ∼4.0% (Cd) after optimization of the operating conditions. The recommended approach has been applied to directly determine the trace elements of interest in the Chinese traditional medicine Loulu and in the solid biological standard reference material (peach leaves, GBW 08501) with satisfactory results. Received: 28 December 1998 / Revised: 9 February 1999 / Accepted: 12 February 1999     

聚氯乙烯/木纤维复合材料的研究Ⅰ.硬脂酸和ABS改性木纤维对复合材料力学性能的影响

为改善聚氯乙烯（PVC）和木纤维两者的界面亲合性，提高PVC／木纤维复合材料的机械力学性能，分别用硬脂酸和ABS来改性木纤维的表面，研究发现用硬脂酸处理木纤维可提高复合材料的拉伸强度，但对复合材料的冲击强度影响不大．ABS处理木纤维可同时提高复合材料的拉伸强度和冲击强度。本文也研究了改性剂用量和木纤维含量对复合材料力学性能的影响。     

硅胶-TBP 反相萃取层析分离法测定金(Ⅲ)与铊(Ⅲ) 的研究

以王水（体积分数为２０％）作移动相,以硅胶球负载的ＴＢＰ作固定相,反相萃取层析使微量Ａｕ（Ⅲ）、Ｔｌ（Ⅲ）与Ｆｅ３＋、Ｃｕ２＋、Ａｇ＋、Ｚｎ２＋、Ｍｎ２＋、Ｈｇ２＋、Ｃｄ２＋、Ｐｂ２＋、Ｓｂ５＋、Ａｓ５＋、Ｇａ３＋、Ｉｎ３＋、Ｐｔ２＋、Ｐｄ２＋等多种离子分离,留于柱上的铊、金分别用ＮａＡｃ溶液（量浓度为１ｍｏｌ／Ｌ）及Ｎａ２ＳＯ３溶液（质量浓度为１０ｇ／Ｌ）洗脱进行连续分离与测定（结晶紫光度法测定铊,孔雀绿光度法测定金）,回收率可达９６％以上,方法已应用于地质样品中金、铊的连续分离与测定。     

Phenolic Components from Rhododendron latoucheae Part 5 in the series Chemical Studies on Ericaceae Plants

Chemicalc0mponentsofthegenusRhododendronwithvariousbioactivities,suchasantitussiveandantitracheitishavebeenidentifiedbefore'.T0thebestofourkn0wledge,theplantRhododendronlatoucheaeFinetetFranchofthegenushasnotbeenstudiedchemicallyupt0n0w.Wehereinrep0rtthestructuraIelucidationoftw0newnaturalphen0licc0mpoundsnamed( )-rhodolat0uchollandisoepirh0d0dendrin4fromtheleavesofR.laloucheae.Besides,sixotherknownc0mpounds,( )-rh0d0dendr0l2,epirh0d0dendrin3.4-(3'-O-0-D-glucopyranosyl-4'-hy5,4-(4'-O-6-D-g…     

Synthesis of α-Selenoesters and α-Thiolesters via Sm/SbCl_3 System in Aqueous Media

SincethefirstBarbier-typereacti0ninaqueousmediainl977',organometallicreactionshaveattractedconsiderableattentioninorganicsynthesis'.lfonecanperformorganometallic-typereactionsinaque0usmediajustasgeneralIyandeasilyasin0rganicsoIvents,suchreactionsmay0fferconsiderableadvantagesf(l)Thereisthepracticalconvenienceofnothavingtohandleinflammableandanhydrousorganicsolvents.(2)Thetedioustaskofprotection-deprotectionchemistryforcertainfunctionalgroupsoftenenc0unteredin0rganicsynthesismaynotberequired.(…     

煤—焦炉气共热解特性研究：Ⅲ.热解焦油分析

采用色－质联用技术分析先锋褐煤在焦炉气气氛下热解油品的组成及其相对含量，主要考察了不同热解压力和升温速率对油品组成的影响并与相当氢分压下的加氢热解油品分析结果比较。结果表明，煤－焦炉气共热解焦油中含有非常丰富的苯、甲苯、二甲苯（ＢＴＸ），酚、甲酚、二甲酚（ＰＣＸ）以及萘。热解压力和升温速率对油品的组成及其相对含量有较大的影响。在实验条件下，压力升高和升温速率降低均有利于焦油中ＢＴＸ、ＰＣＸ和萘实际     

Chemistry of O-Benzoquinones and Masked O-Benzoquinones I. Diels-Alder Reactions of O-Benzoquinones with Dimethyl Acetylenedicarboxylate and Phenylacetylene

Diels-Alder reactions of six o-benzoquinones with dimethyl acetylenedicarboxylate has been examined. The yields of adducts vary with the natures of the o-benzoquinones, 3,4-Di-n-propyl-(1c), 3,6-di-n-propyl (1d). 3. 4-diallyl-(1e) and 3, 6-diallyl-o-benzoquinone (1f) are found to give bicyclic a-diketones exclusively without the formation of 1,4-dioxine derivatives, the yields ranging from 20 to 70%. In the case of 4, 5-dimethoxy-o-benzoquinone, dimethyl 4, 5-dimethoxyphthalate is produced in 42% yield, presumably derived from the decomposition of the corresponding initially formed α-diketone. 3, 6-Di-n-propyl-4, 5-dimethoxy-o-benzoquinone deteriorates without addition to dimethyl acetylenedicarboxylate upon heating. The additions of o-benzoquinones 1c , 1d and 1f to phenylacetylene are also studied. The yields of adducts, α-diketones, range from 23% to 82%.     

Chemistry of O-Benzoquinones and Masked O-Benzoquinones IV. Synthesis of O-Spirodienonelactones from Unsymmetric Catechols

We describe the syntheses of 6, 8-di-tert-butyl-, 7, 9-di-tert-butyl., 6,7-di-n-propyl and 8, 9-di-n-propyl-O-spirodienonelactone from 3, 5-di-tert-butylcatechol and 3, 4-di-n-propylcatechol.