前线分子轨道(FMO)在有机电环化反应中的应用

本文通过电环化反出实例,应用前线轨道理论清楚地解释了该反应中的高度立体选择性问题。阐述了前线分子轨道对探讨有机反应机理和预测产物构型的重要作用。     

电环化反应规律与教学实践

电环化反应是周环反应的一类,对于理解和掌握分子轨道理论非常有帮助,掌握了不同P电子的分子轨道形状和能量,但快速准确得到电环化反应立体结构产物也是不易的。分子轨道是原子轨道的线形组合,采用前线轨道理论解释电环化反应机理,并根据前线轨道对称性判别反应中分子轨道的旋转方式,从而得到立体专一性结构的产物。     

计算化学和虚拟仿真技术在制药工程专业有机化学教学中的应用实践

随着现代科技的迅速发展,计算化学和虚拟仿真技术在基础化学教学中的应用越来越广泛.借助于计算化学和虚拟仿真技术,可将有机化学中抽象的分子结构、分子轨道、反应机理等直观化,从而使相关知识点更容易理解和掌握.本文以绝对构型的判断、构型与构象的区分、反应机理的动态演示为例,对计算化学和虚拟仿真技术在制药工程专业有机化学课程教学...     

有机教材反应机理描述及其存在的问题与解决办法

反应机理是各个基元反应的集成。化学反应的本质是旧键的断裂与新键的形成。因此,无一个基元反应不涉及共价键改变的电子转移过程。电子转移方向必定是由电子源转向电子穴。如果将电子与轨道看作特殊的基团,那么,每一个基元反应可看作是一个简单的取代反应。本文对有机教材反应机理描述存在的问题进行剖析并提出解决办法,以便有机反应机理描述可以得到统一,有利于有机机理的学习与理解。     

Multiwfn在分子轨道理论教学中的应用

分子轨道理论是学生在学习无机化学过程较难理解和掌握的内容,文章使用gaussian和multiwfn软件对分子轨道成分和键级的计算,绘制了分子轨道能级图,并将这部分内容形象直观地呈现出来,有利于增加学生学习的主动性和积极性,提高教学质量.     

羧基羟肟酸浮选一水硬铝石高岭石的理论研究

通过密度泛函和分子动力学模拟方法,计算了药剂分子与一水硬铝石和高岭石的相互作用。得到了分子的稳定构型,最低空轨道,最高占据轨道,体系结合能,相互作用的相关联函数等数据.从理论角度解释药剂与矿物作用的机理。     

甲醇制烯烃、二甲醚反应机理研究新进展

正国家能源集团集团公司教授级高级工程师贺振富,利用杂化轨道理论研究"甲醇制烯烃反应机理研究"和"甲醇制二甲醚反应机理研究"等相关工作中发现了中间产物C↑↓~〇H_2,定义为He-form,C↑↓~〇H_2结构中碳原子外层有一对孤对电子和一个空轨道,↑↓代表孤对电子,〇代表空轨道。C↑↓~〇H_2是构成烯烃和醚类化     

膦铑催化剂对丁二烯系共聚物中C=C键加氢的模拟研究

采用分子模拟方法研究对C=C键的催化加氢过程,构建了各基元反应中的分子模型,并通过构建动力学模型计算了各分子所具有的能量,从而计算出各基元反应的能量变化,揭示了各基元反应的机理,最终解释三苯基膦氯化铑催化剂在丁二烯系共聚物中对C=C键催化加氢的反应机理。     

利用简化分子轨道对称性的表示方法——前线轨道奇偶性解释周环反应的立体化学

本文提出了新的分子轨道对称性的表示方法——-前线轨道的奇偶性来快速准确的确定周环反应的立体化学,任何开链共轭多烯烃:当分子轨道为奇数(ψ1、ψ3…)时,两端位相相同;当分子轨道为偶数(如ψ2,ψ4…)时,两端位相相反。它可用于解释Woodward一Hoffmann规则和周环反应的机埋,简单易懂,在周环反应的教学中发挥了较好的作用。     

密度函数方法研究第一副族过渡金属二聚物的电子结构和光谱特性

密度函数理论计算了 Cu2 ,Ag2 和 Au2 二聚物的电子结构和光谱性质。结果表明 ,随着电子数的增加 ,相对论效应也在增加。使用 ZORA相对论方法可以得到可靠的电子结构。应用 B3 LYP作为交换 -相关函数 ,Cu2 ,Ag2 和 Au2 三个二聚物分子得到了相同的轨道能级顺序。在该族双分子化合物中全充满的 d电子不是完全惰性的。d电子在这三个分子当中对前线分子轨道的贡献也是完全不同的。同时由于 d电子和 s电子强相互作用引起 d型分子轨道的向上移动和 S型分子轨道向下移动。结果还表明 ,对于 Cu2 和 Au2 来说 ,d-型分子轨道和 S-型分子轨道的能级是非常接近的 ,这导致上述轨道在激发状态下很多相似的特性。而对于 Ag2 来说 ,d-型分子轨道和 S-型分子轨道能级较大的差表明 d电子对前线分子轨道只有极其微小的贡献。通过 TDDFT和 DSCF方法 ,确定和归属了低激发态的光谱项 ,并通过 s-和 d电子对这些激发态的贡献解释了光谱项的性质。目前研究得出的计算结果与实验数据非常吻合     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料，介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比，介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序，对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

Inorganic/organic nanocomposite coatings: The next step in coating performance

Inorganic/organic hybrid materials have considerable promise and are beginning to become a major area of research for many coating usages, including abrasion and corrosion resistance. Our primary approach is to prepare the inorganic phase in situ within the film formation process of the organic phase. The inorganic phase is introduced via sol-gel chemistry into a thermosetting organic phase. By this method, the size, periodicity, spatial positioning, and density of the inorganic phase can be controlled. An important aspect of the inorganic/organic hybrid materials is the coupling agent. The initial task of the coupling agent is to provide uniform mixing of the oligomeric organic phase with the sol-gel precursors, which are otherwise immiscible. UV-curable inorganic/organic hybrid systems have the advantages of a rapid cure and the ability to be used on heat sensitive substrates such as molded plastics. Also, it is possible to have better control of the growth of the inorganic phase using UV curing. It is our ultimate goal to completely separate the curing of inorganic and organic phases to gain complete control over the morphology, and hence optimization of “all” the coating properties. Thus far, it has been found that concomitant UV curing of the inorganic and organic phases using titanium sol-gel precursors afforded nanocomposite coatings which completely block the substrate from UV light while maintaining a transparent to visible light. Also, it has been found that the morphology of the inorganic phase is highly dependent on the concentration and reactivity of the coupling agent. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004, in Chicago, IL.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Some Large Wood-Boring Beetles in Southeastern USA

Ethanol and α-pinene were tested as attractants for large wood-boring pine beetles in Alabama, Florida, Georgia, North Carolina, and South Carolina in 2002–2004. Multiple-funnel traps baited with (−)-α-pinene (released at about 2 g/d at 25–28°C) were attractive to the following Cerambycidae: Acanthocinus nodosus, A. obsoletus, Arhopalus rusticus nubilus, Asemum striatum, Monochamus titillator, Prionus pocularis, Xylotrechus integer, and X. sagittatus sagittatus. Buprestis lineata (Buprestidae), Alaus myops (Elateridae), and Hylobius pales and Pachylobius picivorus (Curculionidae) were also attracted to traps baited with (−)-α-pinene. In many locations, ethanol synergized attraction of the cerambycids Acanthocinus nodosus, A. obsoletus, Arhopalus r. nubilus, Monochamus titillator, and Xylotrechus s. sagittatus (but not Asemum striatum, Prionus pocularis, or Xylotrechus integer) to traps baited with (−)-α-pinene. Similarly, attraction of Alaus myops, Hylobius pales, and Pachylobius picivorus (but not Buprestis lineata) to traps baited with (−)-α-pinene was synergized by ethanol. These results provide support for the use of traps baited with ethanol and (−)-α-pinene to detect and monitor common large wood-boring beetles from the southeastern region of the USA at ports-of-entry in other countries, as well as forested areas in the USA.