高锰酸钾氧化法合成2-甲酸吡啶

以2-甲基吡啶为原料,水为溶剂,经80℃下高锰酸钾氧化和乙醇重结晶得到2-甲酸吡啶;采用红外光谱仪和核磁共振谱仪表征了目标产物的结构;考察了高锰酸钾用量、溶剂用量和反应时间对产物收率的影响,讨论了重结晶试剂的选择,进而确定了合成2-甲酸吡啶的较优条件.结果表明:以水作反应溶剂,控制原料和高锰酸钾的摩尔比为1∶2.3时,反应时间为5~6 h,以乙醇重结晶,目标产物的总收率达79.7%.     

铜催化炔基溴与丙炔醇的偶联-异构化反应合成戊炔烯酮

乙炔溴和丙炔醇在哌啶溶剂中,用醋酸铜作催化剂,能够发生偶联-异构化反应获得具有立体选择性的唯一产物(E)-1,5-二取代-戊-2-烯-4-炔-1-酮.机理研究表明,哌啶在反应体系中起到了溶剂和碱的双重作用.该反应具有简单、高效、反应范围宽泛等特点,能够以40%~83%的产率获得目标产物反式1,5-二取代的戊炔烯酮.     

亲核试剂的亲卤反应2, 冠醚促进的二氟二溴甲烷与硫酚钠的反应

在苯、乙醚等溶剂中,CF_2Br_2与 PhSNa不反应或反应极慢.加入催化量的二苯并-18-冠-6,则反应在数分钟内完成,主产物 PhSCF_2Br 的产率提高至75～85%,副产物 PhSCF_2H 及 PhSSPh受到显著抑制.本体系明显优于最近文献报道的其他反应体系.讨论了反应机理,给出了表明反应主要是阴离子型链式机理的进一步证据:反应速度和产物分布对水、醇等给质子性杂质敏感,对氢原子供体型溶剂及光、氧、自由基捕获剂不敏感;在以 CCl_4为溶剂的反应中,得到 PhSCF_2Cl 和属于~-CCl_3的产物,而未检测到自由基型机理所预期的 CCl_3CCl_3.     

3-羟基-6-O-甲基红霉素的合成优化与副产物的分析

分别以甲醇和水为溶剂,探讨了克拉霉素脱克拉定糖反应的主要产物,结果发现:以甲醇为溶剂得到的不是3-羟基-6-O-甲基红霉素,而是3-羟基-8,9,10,11-二脱水-9,12-半缩酮-6-O-甲基红霉素.以水为溶剂得到了3-羟基-6-O-甲基红霉素,收率94.7%.     

离子液体-乙腈混合溶剂中电催化CO2与甲醇合成碳酸二甲酯

常温常压下分别在离子液体 1-丁基-3-甲基咪唑四氟硼酸盐([bmim]BF4)-MeCN混合溶剂和纯MeCN溶剂中研究了CO2在Cu电极上的循环伏安行为. 结果表明, CO2均发生不可逆还原反应生成CO-2. 与纯MeCN溶剂相比,在混合溶剂中CO2还原峰电位均有正移. 这表明溶剂中的咪唑型离子液体对活化CO2有催化作用. 在混合溶剂中,以CO2和MeOH为原料合成碳酸二甲酯(DMC), 考察了[bmim]BF4/MeCN体积比、工作电极材料、 MeOH浓度和电解电位等对DMC产物收率的影响. 与其他DMC合成方法相比,本法反应条件温和、设备简单、合成产物收率较高. 在优化的条件下, DMC产物收率可达79.6%. 并提出了合成DMC可能的反应机理.     

含咔唑基苯并咪唑衍生物的合成

以咔唑为原料,经烷基化、甲酰化反应合成N-烃基咔唑-3-甲醛;无催化剂条件下,N-烃基咔唑-3-甲醛与邻苯二胺经缩合-环化"一锅"反应合成了两类新型含咔唑单元的苯并咪唑衍生物.研究了溶剂选择、溶剂用量、反应温度、反应物配比等因素对缩合-环化反应结果的影响;通过改变两种反应物的等物质的量比可选择性地得到以其中一类苯并咪唑衍生物为主的产物.     

溶剂和酰基受体对α-氰基-3-苯氧基苄醇乙酯的酶促对映体选择性转酯化反应的影响

研究了在有机溶剂中固定化Alcaligenes sp.脂肪酶催化α-氰基-3-苯氧基苄醇乙酯的对映体选择性转酯化反应,考察了不同性质的溶剂和酰基受体对酶的催化活性和选择性以及对产物稳定性的影响.结果发现在弱极性溶剂如正己烷中酶具有较高的催化活性但产物e.e.%值低,而且容易分解;在四氢呋喃等溶剂中酶催化活性相对低,但产物e.e.%值高,也较为稳定;但反应时间太长,会导致产物分解及纯度下降;不同酰基受体对酶反应无显著影响,甲醇为最佳酰基受体,太多醇会导致反应速率下降;溶剂水含量大于2.0%时对酶活性和产物稳定性产生明显不利影响.在优化条件下,酶反应可得到(S)-α-氰基-3-苯氧基苄醇产率＞48%,纯度＞99%e.e.     

对苯二酚催化加氢制备1,4-环己二醇的研究

对Pt/C、Pd/C、Ru/C、Rh/C和Raney Ni几种催化剂,以及以钌为活性组分的催化剂载体如活性碳、SiO2、Al-MCM-41、ZSM-5、MgO、TiO2在对苯二酚加氢反应中的催化活性进行了比较.结果表明Ru/C催化剂的催化活性和对目的产物的选择性最好.对Ru/C催化剂催化对苯二酚加氢反应的反应条件如反应温度,氢气压力,反应溶剂,反应时间等对反应转化率和产物选择性的影响进行了讨论.反应的适宜条件为:反应物和催化剂的物质量比为367∶1,温度为150℃、氢气压力5 MPa,乙醇为溶剂,反应时间2 h.在此反应条件下,对苯二酚的转化率为98.8%,目的产物1,4-环己二醇的选择性为77.7%.并根据产物随时间的变化规律对该反应路径进行了分析.     

奎宁修饰型Pt/Al2O3催化丙酮酸乙酯不对称加氢反应：乙酸溶剂与甲苯溶剂的比较

采用奎宁修饰型Pt/Al_2O_3作为加氢催化剂在常温常压下比较了乙酸和甲苯溶剂中丙酮酸乙酯的不对称加氢与一般的加氢反应的反应结果;研究了反应对映选择性与底物转化率的关系、丙酮酸乙酯用量对产物对映选择性的影响、三乙胺的作用以及乙酸-甲苯混合溶剂的使用. 实验结果表明, 乙酸作为反应溶剂的性能优于甲苯且溶剂化作用强于甲苯;两种溶剂中的不对称加氢反应均存在初始过渡期, 以乙酸为溶剂时, 催化反应速度较快;在乙酸溶剂中底物用量对产物对映纯度影响不大, 在甲苯溶剂中底物用量具有最佳值;在乙酸溶剂中加入三乙胺能显著提高反应的对映异构体选择性而在甲苯溶剂中则没有促进作用.     

乙酸氧钒催化α-蒎烯与过氧化氢烯丙位氧化的介质效应

以乙酸氧钒为催化剂,过氧化氢为氧化剂,研究了α-蒎烯的氧化反应.考察了以4个碳原子的有机物丁酮、乙二醇二甲醚、乙酸乙酯、1,4-二氧六环、四氢呋喃、叔丁醇和二氯甲烷作为溶剂构成反应介质,以及溶剂用量、反应温度和反应时间等因素对催化性能的影响,发现在醚类和乙酸乙酯中乙酸氧钒对α-蒎烯与过氧化氢的烯丙位氧化具有优良催化作用.结果表明,在催化剂用量为10.0%、反应温度为40℃、乙二醇二甲醚为溶剂、反应8 h时α-蒎烯转化率达82.9%,主要烯丙式氧化产物的选择性达73.5%,其中马鞭草烯酮、马鞭草烯醇和龙脑烯醛的选择性分别为45.9%、17.3%和10.3%.     

Thermoanalytical investigation of lyotropic liquid crystals and microemulsions for pharmaceutical use

The interactions between surfactant and water were studied thermoanalytically focusing on the lyotropic liquid crystalline and microemulsion region in four ternary systems containing Cremophor EL and Cremophor RH40 as surfactants, neutral oil and isopropyl myristate as oily components. Subzero temperature DSC (SZT-DSC) measurements were carried out to determine the quantity of the bound water forming a hydration layer in surfactant microstructures, and the amount of free water, which has physico-chemical properties not much different from those of pure water. The variation of the surfactant:bound water ratio in the function of water concentration was also investigated. Phase changes detected by the SZT-DSC measurements were confirmed by polarization-microscopic and rheological investigations.     

3-甲基吡啶在有机物/水混合溶剂中的电氧化

在质子交换膜为隔膜的电解槽内,以丙酮、乙腈和2-丁酮与水分别构成混合溶剂体系,通过循环伏安和恒电位电解实验,探索了3-甲基吡啶在混合溶剂中在PbO2电极上的电氧化条件,并与纯水溶剂的情况相比,研究了氧化电流密度及生成烟酸的选择性和电流效率的变化.     

Does magnetic treatment of water change its properties?

Some properties and functions of water treated under magnetic field were examined. No change in properties of pure water distilled from ultrapure water in vacuum was observed by magnetic treatment. However, when the same magnetic treatment was carried out after the distilled water was exposed to O2, water properties such as vibration modes and electrolytic potential were changed. The degree of magnetic treatment effect on water was quantitatively evaluated by contact angle.     

Sorption and transport of water in nylon-6 films

Sorption and transport properties of water through films of Nylon-6 were obtained at 5, 23, and 40°C. Commercially available films were used and a Cahn electrobalance was employed for measuring the water uptake by the polymer samples. Values of the water sorption isotherms are accurately described by the Langmuir/Flory-Huggins dual-mode sorption model. At water activity values below 0.15, the volume fraction of water described by the Langmuir portion of the model was greater than the Flory-Huggins population. Solubility and diffusion coefficients of water, as well as the diffusion activation energy and enthalpy of dissolution of water for Nylon-6, were determined from the sorption experiments. Values obtained support the hypothesis of a bimodal water sorption mode, and the formation of water clusters. © 1994 John Wiley & Sons, Inc.     

The determination of lead in water and sediment samples using a lead ion-selective electrode

Lead concentrations in water and sediment samples near a stationary metal emission source were determined using the lead ion-selective electrode. These results were then verified by use of atomic absorption spectrophotometric methods. Samples were collected at three strategic sites near a local lead company in Southeast Houston, Texas. Accumulated rain water and sediment (soil deep down core) were analyzed in order to estimate lead concentration as a function of depth. Data indicate that the level of lead concentrations in both surface water and water extracted from the sediments exceed the limits for drinking water as established by the Environmental Protection Agency. The lead concentrations of the soil samples were higher in most cases when compared with various soils in the United States. The highest concentrations of lead were found in surface water samples.     

酒石酸和氰基二苯基二氢吡唑的高效液相色谱手性分离

以不同配比的甲醇和水作洗脱液,对手性物质酒石酸和5-氰基-1,3-二苯基-4,5-二氢吡唑进行了手性色谱柱高效液相色谱分离。对于亲水性的酒石酸,以纯水作为洗脱液,手性异构体不能得到分离;洗脱液中甲醇的含量增加到50%,D-和L-异构体得到分离,但是内消旋异构体和D-异构体仍然混在一个峰中;以100%甲醇作洗脱液,酒石酸的内消旋及D-和L-三个异构体的色谱峰全部分开。对于憎水性的5-氰基-1,3-二苯基-4,5-二氢吡唑,以100%甲醇作为洗脱液;当洗脱液中水的含量增加到30%时,R-和S-手性异构体的色谱峰开始分离,但是两个峰大小不相等,分离效果不理想;当洗脱液中水的含量增加到35%时,R-和S-手性异构体的色谱峰分离为两个大致相等的色谱峰,但是两个色谱峰仍有部分交叠。保留时间加长,有利于对映异构体的分离,保留时间长的色谱峰变宽。     

近临界水中苯甲醛与丙酮的Claisen-Schmidt缩合反应

在近临界水中进行有机合成为可持续化学合成提供了新的途径。对近临界水中苯甲醛与丙酮的Claisen-Schmidt缩合反应的研究表明,在没有外加任何催化剂的条件下,苯甲醛与丙酮可顺利地发生缩合反应,近临界水在其中兼作溶剂和催化剂,避免了碱催化剂的使用和随后繁杂的中和、分离步骤以及产生废弃盐等弊端。温度、反应时间和初始水量对反应的转化率和苯丁烯酮的产率有不同的影响。     

Drinking water quality from the aspect of element concentrations

Summary Drinking water in developed countries is usually treated by the water-purification system, while in developing countries untreated natural water such as well water, river water, rain water, or pond water are used. On the other hand, many kinds of mineral water bottled in plastic containers are sold as drinking water with or without gas in urban areas in many countries. Seawater under hundreds meters from the surface is also bottled and sold as drinking water with advertising good mineral balance. Various element concentrations in water samples for drinking were analyzed, and then it was considered the effects of elements on human health.     

饮用水中挥发性有机物(VOCs)的GC-MS分析

用顶空－毛细管气相色谱－质谱联用仪测定了北京主要区域的自来水,北京目前市场销售的瓶装饮用水（包括天然矿泉水,纯净水等）中２３种挥发性有机物（ＶＯＣｓ）（包括有机氯化物,有机溴代物及苯系物等）的浓度,并与其它城市（如天津,上海,兰州等地）的自来水中ＶＯＣｓ的浓度进行了比较,结果表明北京市区内自来水及大多数市售瓶瓶饮用水中ＶＯＣｓ含量很低。     

Interaction between water and polymer chains in poly(hydroxyethyl acrylate) hydrogels

Polymer networks of different cross-linking densities were prepared by copolymerisation of hydroxyethyl acrylate and ethylene glycol dimethacrylate. The average molecular weight between cross-links as well as the polymer chain mobility were characterised by means of dynamic–mechanical spectroscopy. Equilibrium sorption isotherms and the water uptake in immersion in liquid water allowed the determination of the Flory–Huggins interaction parameter between water molecules and polymer chain segments, which decreased with the water activity in the hydrogel and increased with the cross-linking density as a consequence of the hydrophobic character of the cross-linking agent. Dynamic sorption and desorption experiments were used to determine the diffusion coefficient. Received: 11 November 1999 Accepted: 28 July 2000