立体化学教学中易混淆的一些概念

立体化学教学中易混淆的一些概念彭万华（湖北三峡学院化学系宜昌４４３０００）杨小平谭凤姣（湘潭师范学院化学系４１１１００）自从范荷夫（Ｖａｎ＇ｔＨｏｆ）和勒贝尔（ＬｅＢｅｌ）提出一切分子都具有三维结构的论点以来，立体化学开始迅猛发展，并成为一门独立的学...     

有机立体化学教学中手模型的设计与应用

介绍一种通过手势建立＂手模型＂的方法。该法方便、直观、易于掌握,可用于有机立体化学的教学,帮助学生理解有机化合物的立体结构和有机反应的立体化学过程。     

立体化学教学中空间感观能力的培养

介绍了在有机物结构、有机反应机理和构象快速转换平衡的教学中培养学生构建空间感观的策略.教学实践表明,这些策略的实施具有较好的效果.     

启发式教学在立体化学手性分子教学中的应用

以有机立体化学中的手性分子教学为例,探讨兴趣启发、重点启发、问题启发和规律启发法等多种启发式教学方法在立体化学教学中的运用,以培养学生发现问题、分析问题、解决问题和创新的能力。     

立体化学教学中不对称催化科研成果的融入

在基础有机化学教学中引入不对称催化的概念和科研成果,可将立体化学融入贯穿到有机化学课程的章节教学中,丰富立体化学的教学内容。通过对知识点的串联解析使学生了解不对称催化反应,从而逐步加深对立体化学的理解。组织相关研究方向的学术专题报告和科研实践,不仅有助于巩固相关理论知识,还可以让学生在知识熏陶和实验实践中培养自身的学术素养和科研能力,提高学习热情和积极性。     

折纸教具在立体化学中的应用——一种好的教学手段

一种折纸教具模型，能用来代替Ｋｅｋｌｅ模型和Ｓｔｕａｒｔ模型，十分方便地解决了立体构象和在合成中立体控制的教学难点。这是一种新的折纸教具模型系列     

超共轭作用的立体化学

介绍了超共轭作用对决定化合物和反应活性中间体的构型与构象所起的作用并举例说明了超共轭作用对有机反应立体化学的影响.     

谈化学教学语言的运用规范

结合教学实际讨论了合理运用教学语言的重要性和化学教学语言的运用规范,其中包括教学语言的科学性、启发性、教育性、趣味性、节奏感等。     

光环加成反应的立体化学

本文根据微扰分子轨道理论(PMO)及前线分子轨道理论(FMO)从烯类的二聚、烯烃的交叉偶合及与酮及硫酮的反应等三方面来阐述[2+2]光环加成反应的区域选择、位置选择、及立体选择性。     

Stereochemistry of [2,3]Sigmatropic Rearrangements

Stereoselective synthesis is attracting more and more attention. Successful stereoselective syntheses require the availability of reactions of known stereochemistry which give maximum yields of the desired products. This is particularly so with reactions proceeding via cyclic transition states. Of these, the stereochemistry of [3,3]sigmatropic processes has long been known. This article now summarizes the factors determining the stereoselectivity of [2,3]sigmatropic rearrangememts.     

Mechanisms and Stereochemistry of Heterolytic Fragmentation

Heterolytic fragmentation can proceed by several mechanisms. A study of the solvolysis of γ-aminoalcohol derivatives N? C? C? C? X, where X equals halogen or ? OSO₂R, shows that fragmentation may occur by a one-step mechanism or by several multi-step mechanisms depending on structural, electronic, and steric factors. The one-step synchronous mechanism has rigorous stereoelectronic requirements. It is associated with an increased reaction rate as evidenced by the “frangomeric” effect. Ketoxime derivatives RR′C?N? X may undergo Beckmann fragmentation by the synchronous mechanism or by prior rearrangement depending on their α-substituents. Fragmentation is frequently accompanied by conventional substitution, elimination, and rearrangement reactions. Under such circumstances knowledge of all possible mechanisms of a given substrate is essential to bring about a desired transformation.     

Stereochemistry of heterometallic platinum clusters

Heterometallic platinum complexes cover a huge field, as shown by a recent survey covering the crystallographic and structural data of almost 1500 examples. About 5% of those complexes exists as isomers and are summarized in this review; except one cis-trans example, the remainder are distortion isomers. These are discussed in terms of the coordination about the platinum atom, and correlations are drawn between donor atom, bond lengths and interbond angles, with attention to trans effect and metal-metal bonds. Distortion isomers, differing only by degree of distortion in Pt–L and Pt–M distances and L–M–L bond angles, spread over a wide range of oxidation states of platinum: zero, +1, +2 (most common) and +4. The mean Pt–Pt bond distance elongate with increase in oxidation state of platinum: 2.705 Å (Pt(0)–Pt(0)) < 2.720 Å (Pt(I)–Pt(I)) < 2.773 Å (Pt(II)–Pt(II)). The shortest mean Pt–M bond distances are: Pt(0)–Ga = 2.37 Å; Pt(I) = Au 2.697 Å, Pt(II)–Fe = 2.625 Å and Pt(IV)–Sn, 2.580 Å.     

立体化学中的反式共平面

从广义的角度讨论了消除反应、重排反应、亲电加成反应和邻基参与反应中的反式共平面现象,揭示了这些反应立体化学过程的共性。     

Recent Developments in the Stereochemistry of Cyclopropane Ring Opening

This review article deals with the stereochemistry of the following ring opening reactions: 1. Homoallylic rearrangement of secondary and tertiary cyclopropyl alcohols in the presence of electrophilic reagents, 2. The addition of carboxylic acids to vinylcyclopropanes, 3. The thermal rearrangement of vinylcyclopropanes into cyclopentenes. An account is also given of the NMR spectroscopic determination of the conformations of substituted vinylcyclopropanes.     

Memory Effects and Stereochemistry in Multiple Carbonium Ion Rearrangements

The stereochemical configuration at the initial site of heterolysis in a carbonium ion process in solution controls the specificity of migration two steps later in many sequential multiple rearrangements. These “memory effects” are attributable to the presence on the potential energy surface of small, hitherto undetectable minima. A variety of structural, stereochemical, and isotopic marking techniques are used to demonstrate that memory effects are a general feature of the ring-expansion route to bicyclic carbonium ions. The intermediates formed in these reactions, although necessarily symmetrical or quasi-symmetrical at equilibrium, act unsymmetrically. The memory effect uses the rate of an intramolecular carbonium ion rearrangement as a calibration with which to compare the rate of symmetrization. In this way, the system functions as a sensor of sub-species.     

Stereochemistry of Acetone Condensation on Solid Base Catalysts

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