农药中间体3,5,6-三氯吡啶-2-醇钠的合成进展

介绍了农药中间体3,5,6-三氯吡啶-2-醇钠的合成路线和合成方法,并详细讨论了在催化剂条件下用三氯乙酰氯和丙烯腈三步法合成三氯吡啶醇钠的方法.     

3—正丙基—5—羟基—1—甲基比唑的合成研究

以2－戊酮和草酸二乙酯为起始原料，经Claisen缩合，环化，甲基化和皂化等反应制得目标化合物3－正丙基－5－羟基－1－甲基吡唑3。文献报道的合成方法为四步法，在此基础上加以改进，形成了两种新的合成路线，即三步法和两步法，其收率均高于四步法，高出27．0％。     

2-(3-氟-4-苯基)苯丙酸合成

二步法合成2-（3-氟-4-苯基）苯丙酸，收率50％（以4-溴-2-氟联苯计）     

1,2,3,4-丁烷四羧酸的合成研究

1，2，3，4-丁烷四羧酸是一种重要的化工产品，本文报道了其三步法的合成方法，收率较国内其它合成法有较大程度的提高，产物分子结构用元素分析、熔点、红外光谱(IR)、核磁共振谱(^1HNMR)进行了鉴定，表明结果与预期产物相符。     

萃取剂2-羟基-5-壬基苯乙酮肟的合成

本文以4-壬基酚、乙酰氯、无水AlCl3和盐酸羟胺为主要原料合成了2-羟基-5-壬基苯乙酮肟（HNAO）。合成2-羟基-5-壬基苯乙酮（HNA）时，采用了-步法，以四氯乙烯为溶剂，n（4-壬基酚）：n（乙酰氯）：n（AlCl3）=1：2：1．2，加毕AlCl3后补加4-壬基酚物质量0．2倍的乙酰氯，回流温度下（120℃）反应6h。HNA收率为98．1％，纯度为79．5％。合成HNAO时，以蒸馏的HNA为原料，以甲苯为溶剂，导辛酸钠为相转移催化剂，n（HNA）：n（盐酸羟安）：n（碳酸钠）=1：1．3：0．85，75℃下反应4．5h。HNAO收率为97．9％，纯度为88．6％。FT—IR分析结果表明所得中间体及产物与HNA和HNAO特征相符。     

3-氯-2-(二氟甲氧基)-5-(4,4,5,5-四甲基-1,3,2-二氧戊环-2-基)吡啶的合成研究

3-氯-2-(二氟甲氧基)-5-(4,4,5,5-四甲基-1,3,2-二氧戊环-2-基)吡啶是一种重要医药化工中间体。本文以2-羟基-5-溴吡啶为原料,对目标化合物的合成进行了研究,此合成方法原料价廉易得、操作简单,总收率为53.15%,适合工业化生产。     

20(S)-7-丙基-10-羟基喜树碱的制备研究

以 2 0 (S) 喜树碱为原料 ,通过丙基化反应、氧化反应及光化重排反应三步法 ,制备了 2 0 (S) 7 丙基 10 羟基喜树碱 ,改进后的合成收率从文献报道的 2 0 3 %提高到 3 2 8%。     

2-氯-5-甲基吡啶的合成方法

介绍了2-氯-5-甲基吡啶的四种类型的合成方法,包括以3-甲基吡啶-N-氧化物为原料的氯化法、2-氨基-5-甲基吡啶氯化法、环合氯化法、3-甲基吡啶直接氯化法等     

聚二(2-甲基-4-羟基-5-叔丁基苯)硫醚的合成

介绍了四步法合成聚二(2 甲基 4 羟基 5 叔丁基苯)硫醚:①以异丁烯和间甲酚为原料,以浓硫酸为催化剂合成3 甲基 6 叔丁基苯酚,并将剩余釜底液继续与间甲酚反应使3 甲基 6 叔丁基苯酚的收率接近100%;②硫磺与氯气反应合成二氯化硫,收率80%以上;③3 甲基 6 叔丁基苯酚与二氯化硫发生缩合反应生成二(2 甲基 4 羟基 5 叔丁基苯)硫醚,采用加入辅助溶剂法收率达到92%;④二(2 甲基 4 羟基 5 叔丁基苯)硫醚同氧气发生氧化偶联反应合成聚二(2 甲基 4 羟基 5 叔丁基苯)硫醚。氧化偶联反应的最佳条件:n〔二(2 甲基 4 羟基 5 叔丁基苯)硫醚〕/n(氧气)=2 5～3 0,n(氯化亚铜)∶n〔二(2 甲基 4 羟基 5 叔丁基苯)硫醚〕=1∶140,n(氯化亚铜)∶n(四甲基乙二胺)=1∶1 3的铜 胺络合物为催化剂,温度50℃,压力0 2MPa,反应时间2～3h,然后减压蒸出溶剂,最后得到淡黄色的聚二(2 甲基 4 羟基 5 叔丁基苯)硫醚,收率>99%。     

3-羟基-2-萘甲酰腙的合成研究

以3-羟基-2-萘甲酸、水合肼、甲醇、甲基异丁基酮为原料,经三步法(酯化反应、酰肼化反应、酰腙化反应)合成高纯度的目标产物3-羟基-2萘甲酰腙。考察了原料配比、催化剂种类、酯化反应时间、温度等对各反应速率的影响。结果表明,醇酸比为4,催化剂为浓硫酸时,酯化反应更加充分;肼酯比为4时,更有利于酰肼化反应进行;温度为85℃酰腙化反应更加完全。该方法反应条件温和、操作步骤简单,所得产品收率高。     

水氯镁石的热解机理及动力学

采用热重差热质谱联用技术(TG-DTA-MS)和热分析技术(TG-DTA)研究了水氯镁石热解过程的反应机理和动力学行为. 结果显示,水氯镁石热解分4个阶段,前2个阶段共脱除4个结晶水,后2步脱水和水解并存,第1步的分解反应属于球形对称相界面反应为控制步骤的R3机理,后3步属于Avrami-Erofeev的成核及核成长为控制步骤的A1机理,4步表观活化能Ea分别为81.13, 125.4, 230.4和164.1 kJ/mol,频率因子分别为2.95×1010, 2.70×1015, 4.07×1026和4.75×1016 s-1.     

粪大肠菌群检验初发酵与复发酵的结果比较

多管发酵法检验粪大肠菌群实验:比较初发酵、复发酵二步骤的结果,与初发酵直接得出结果的符合率,以便能通过一步法尽快报出结果,做到省时省力。笔者认为大批量采集样品时初发酵产酸产气,便不经复发酵,直接报出结果,可节省时间和人力物力,使检测很快得到结果。     

汽车用清洁燃料——二甲醚

二甲醚是柴油发动机理想的替代燃料,可以由天然气和煤为原料合成制取.综述了二甲醚的两种合成工艺:一步法和二步法.     

热法磷酸生产工艺与装备研究进展

热法是生产高品质磷酸的一种较为便利的方法：评述了热法磷酸生产中具有代表性的燃烧水合一步法和燃烧水合二步法的工艺流程、特点以及生产巾面临的问题。在分析国内外磷燃烧塔现状的基础上，介绍一种借助辐射换热面实现余热回收的新型燃磷塔的结构。指出热法磷酸生产的研究工作应集中于开发节能环保型（无热污染）燃磷塔上。     

Combustion characteristics of jatropha oil droplet at various oil temperatures

Jatropha oil which is a large, branched triglycerides type vegetable oil has good potential as an alternative diesel fuel. Its combustion characteristics have been observed experimentally by igniting the oil droplet of various diameters and temperatures on a junction of a thermocouple. The combustion characteristics are identified from flame image and temperature signal in the center of the droplet. The results show that the jatropha oil droplet performs two steps combustion. Fatty acid burned in the first step and glycerol does in the second step. The onset of micro-explosion occurs shortly before the second step combustion and it becomes more frequent as the oil temperature is increased.     

Ziegler-Natta polymerization: The nature of the propagation step

The paper discusses in detail the nature of the propagation step in Ziegler-Natta polymerization in terms of a one step or two step mechanism. A wide variety of evidence, both earlier literature results as well as current experimental data, is presented in support of a two-step mechanism comprising an initial monomer complexation at the active site followed by insertion into the growing transition metal-polymer bond. The nature of the rate determining step in the polymerization is also considered, and whereas in certain systems at low temperature insertion is clearly the main rate determinant, under other conditions both steps may together determine the overall rate.     

Multistep Model of Cervical Cancer: Participation of miRNAs and Coding Genes

Aberrant miRNA expression is well recognized as an important step in the development of cancer. Close to 70 microRNAs (miRNAs) have been implicated in cervical cancer up to now, nevertheless it is unknown if aberrant miRNA expression causes the onset of cervical cancer. One of the best ways to address this issue is through a multistep model of carcinogenesis. In the progression of cervical cancer there are three well-established steps to reach cancer that we used in the model proposed here. The first step of the model comprises the gene changes that occur in normal cells to be transformed into immortal cells (CIN 1), the second comprises immortal cell changes to tumorigenic cells (CIN 2), the third step includes cell changes to increase tumorigenic capacity (CIN 3), and the final step covers tumorigenic changes to carcinogenic cells. Altered miRNAs and their target genes are located in each one of the four steps of the multistep model of carcinogenesis. miRNA expression has shown discrepancies in different works; therefore, in this model we include miRNAs recording similar results in at least two studies. The present model is a useful insight into studying potential prognostic, diagnostic, and therapeutic miRNAs.     

Thermal Fluctuations in the Structure of Naturally Chiral Pt surfaces

The intrinsic chirality of metal surfaces with kinked steps (e.g., Pt(643)) endows them with enantiospecific adsorption properties. To understand these properties quantitatively the impact of thermally-driven step wandering must be assessed. We derive a lattice-gas model of step motion on Pt(111) surfaces using diffusion barriers from density functional theory. This model is used to examine thermal fluctuations of straight and kinked steps.     

复分解三步循环法生产硝酸钾

介绍了复分解三步循环法生产硝酸钾的生产工艺。和四步法生产硝酸钾工艺比较 ,减少了加料步骤 ,在反应溶液中加入助剂后使溶液中硝酸钾结晶率提高 2 0 %以上。经检测产品质量组成为K2 O 43 0 1 %～ 45 68% ,N 1 3 80 %～ 1 4 2 0 % ,Cl0 3 %～ 2 1 5 % ,H2 O 1 98%～ 3 45 %     

Significantly enhanced energy‐storage density in the strontium barium niobate‐based/titanate‐based glass‐ceramics

Two‐step crystallization process was employed to improve microstructure and energy‐storage density of the strontium barium niobate‐based/titanate‐based glass‐ceramics. By using two‐step crystallization process, the optimum nucleation temperature was obtained to improve dielectric breakdown strength. Compared to the breakdown strength by one‐step crystallization process, the breakdown strength by two‐step crystallization process is increased about 1.89 times with the optimum nucleation temperature. Energy‐storage density of 7.73 ± 0.26 J/cm³ is significantly improved by two‐step crystallization process and is about 2.9 times of 2.63 ± 0.17 J/cm³ by one‐step crystallization process. This result is attributed to the homogeneous nucleation improving the microstructures of glass‐ceramics. Identification and quantification of crystalline phases by using Rietveld refinement reveals the difference of dielectric constants for one‐step and two‐step crystallization processes.