共查询到15条相似文献，搜索用时 109 毫秒
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我们将芳香性概念扩展到全金属团簇Mg3^2-,运用密度泛函理论（B3LYP,B3PW91）对全金属团簇Mg32^-,NaMg3^-和Na2Mg3的稳定结构、振动频率与电子总能量（考虑了零点能ZPE）进行理论计算。计算的结果显示,NaMg3^-和Na2Mg3团簇中包含一个正三角形的阴离子Mg3^2-。对芳香性的平面电子结构、核独立化位移（NICS）以及分子轨道的几个标准模式进行分析,分析的结果指出,2个离域化的π电子遵循4n＋2电子计算规则,并且呈现出π芳香性。 相似文献
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从结构的观点,用符合芳香性的四个判据判别了五员杂环化合物的芳香性,并对其稳定性顺序给予了理论上的解释. 相似文献
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文章提出平面和球面芳香性体系的平面圆环和球形势阱模型，导出芳香性和反芳香性体系的π电子数规则，并半定量解释了苯分子的电子跃迁光谱。 相似文献
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运用密度泛函理论对13种化合物进行几何结构全优化和频率计算,并计算了其芳香性指标NICS（Nucleus-Independent Chemical Shifts）值,研究了取代基对芳香性的影响以及芳香性与分子稳定性的关系。结果表明吸电子基团可以增加苯环的芳香性,供电子基团可以减低苯环的芳香性,随着体系稳定性的增加,苯环的芳香性降低。 相似文献
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本文概述了对芳香性认识的以及各种芳香性判据的优缺点,介绍了非相关性化学位移(Nucleus-Independent Chemical Shifts)以及相关性化学位移(NICS)的解析技术和应用. 相似文献
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许多有机化合物都具有芳香性,正是由于其中很多化合物都散发着芳香的气味。可是,到底要怎样判断一个化合物是否具有芳香性呢？这是许多学生都会遇到的难题。本文不但分析了不同结构类型的芳香化合物,还对休克尔规则中最重要的π电子数的计算方法进行了归纳总结。 相似文献
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食用茉莉花香味成分的GC/MS分析 总被引：6，自引：0，他引：6
采用水蒸气蒸馏-乙醚萃取法对云南引种食用茉莉花中芳香性成分进行了提取，并用气相色谱-质谱联机技术对其中化学成分进行分析鉴定．共鉴定出46种芳香性有机成分，占茉莉花挥发油提取物总含量的99．9005％．通过对食用茉莉花芳香性成分的分析，为茉莉花香精香料的开发提供了依据． 相似文献
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李卫东 《广西师范大学学报(哲学社会科学版)》1991,(Z1)
分析6种判断化合物是否具有芳香性的规则即Dewar共振能、休克尔规则、汉斯的REPE指标、PMO判据、推广的休克尔规则及物理方法,并对各种判据的局限性和优点作了比较。 相似文献
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When students take General Chemistry there are substantially fewer molecular images than they will encounter in Organic Chemistry.
The molecular images Organic Chemistry students see in their textbooks are ones that use dashes and wedges to represent 2D
and semi 3D views, ball and spoke, ball and wire, and structural formulas, to name just a few. They also use physical models
and may also have the opportunity to work with computer generated molecular models. They are expected to understand verbal
instruction connected with the images and at the same time how the verbal explanation fits with the visual image. There has
been little research that combines the use of molecular images of molecules with questions that require organic chemistry
students to understand concepts. This research paper addresses students' understanding of organic chemistry concepts where
ball and wire and ball and spoke visual images of molecules are combined with questions related to the areas of aromaticity,
symmetry, spectroscopy, and shielding. The intention is to provide a basis for assessing students' understanding. 相似文献
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Chi‐hung Clarence Ng 《教育心理学》2008,28(4):439-456
The hypothesis in this study was that different types of multiple‐goal learners would have different patterns of learning. A sample of 797 adult distance learners enrolled in different programs offered by a distance learning university in Hong Kong completed a questionnaire assessing their goals, use of strategies, motivational beliefs, and attitudes towards the course they were doing. Two‐stage cluster analyses found a group of single‐goal learners (mastery focused) and three groups of multiple‐goal learners with different focuses in their goal profiles: performance focus, work focus, and multiple focuses. These four clusters of learners differed in terms of use of learning strategies, regulatory strategies, motivational beliefs, and attitudes towards the course. Learners focusing on work‐related goals or performance goals achieved better examination results than did those focusing on multiple goals or solely on mastery goals. 相似文献