立体化学相关问题及概念解析

立体化学是高校有机化学教学中的一个难点。本文用图示的方式解析了异构体分类问题以及易于混淆的相关概念,明确了立体异构分类方法及各类立体异构体间的从属关系。从宏观和微观两个角度解析了立体化学的相关概念,并探讨了概念间的关联性。     

Fractals and Related Hierarchical Models in Polymer Science

Polymer science, an interdisciplinary science well-rooted in organic chemistry and in materials science, encompasses an inordinate number and diversity of substance classes and thus has far-reaching applications. Interestingly, polymers also represent a great challenge to the theoreticians, since their theoretical treatment often necessitates appropriate extensions of the classical methods from solid state physics and from statistical physics. Thus, new concepts often have to be invoked when considering the special properties of polymers. In this review we concentrate on one of the modern concepts in the theory of polymers, namely on scaling. Scaling is closely associated with new developments in the field of fractals and of hierarchical structures. Such concepts are invaluable for the modeling of complex geometries and for describing dynamical processes in polymeric materials. Here, we focus on a presentation of these ideas and we outline examples of recent research in which these concepts have been successfully applied.     

无机化学四个易混淆基本概念的讲授建议

Fuzzy representation of chemical concepts is an obstacle for learning, and this prevents students from developing strict logical thought. Inorganic chemistry is one of the basic courses for most of first-year undergraduate students of chemistry and related majors. We dissect four common concepts in inorganic chemistry which are easily confused, point out the reasons for the wrong conclusions and give some teaching suggestions. This article helps teachers for clear presentation of these concepts.     

Simulation of organic reactions: from the degradation of chemicals to combinatorial synthesis

Organic reactions can be run under a variety of conditions, from laboratory experiments, through technical processes, to combinatorial chemistry. The scope is further extended when the metabolism of compounds and the reactions in the mass spectrometer are included. We present here several concepts: reactors, phases, and modes, which, together with a kinetic modeling, allow the treatment of such a broad scope of organic reactions. These concepts have been implemented in a knowledge-based system, EROS. Several applications of this system to the wide world of organic reactions are given.     

高分子物理本科教学之我见

高分子物理是一门物理课,其内涵为高分子物质的结构、结构演变与各层次结构单元的运动规律,而非聚合物的"结构与性能"关系.这门课为解释结构与性能关系提供基础概念与理论,但不是"结构与性能"关系本身.这样的定位决定了高分子物理课不应采用系统教学法,而应当采用逻辑教学法,即从一个不证自明的公理(逻辑起点)出发,沿着一条主线,依次导出、建立全部理论体系.在高分子物理中,这个逻辑起点就是长链结构,主线就是熵弹性.故该门课程应按熵弹性这条主线展开.对现行高分子物理课程内容进行分析,大多数内容均可用熵弹性的主线串起来,另外少部分内容也与熵弹性有密切关系.应根据这两点对现行课程体系与教学方法进行改造,为课程各项内容之间建立逻辑关系,方便学生的学习与应用.     

离子的极化和形变

离子的极化和形变是无机化学教学中的一对重要概念,这对概念可以用于解释化合物的结构及许多物理和化学性质。然而一些教科书在介绍这对概念时,大都把极化作用限于阳离子,把形变作用限于阴离子,而忽略了阴离子的极化作用和阳离子的形变作用。同时,在应用这对概念解释化合物结构和性质时,条理上也不十分清晰,甚至还出现自相矛盾的情况,使得学生在学习这对概念时感到困惑。本文介绍了离子的极化和形变这对概念的基本含义,讨论了影响极化能力和形变程度的因素,分析了一些化合物的结构以及溶解度、颜色和热稳定性等物理和化学性质。特别是对一些教学中有争议的问题给出了合理解释。在分析小分子结构时,极化和形变概念的运用可以弥补杂化轨道理论和价层电子对互斥理论的不足。     

Using Molecular Modeling in the Organic Chemistry Course for Majors

Molecular modeling provides a way to correlate theoretical concepts with experimental data; therefore, we have introduced organic chemistry students to molecular modeling early in the first semester. This approach provides students with additional skills for clarifying chemical and theoretical concepts by means of demonstrations in the classroom and hands-on tutorial modules. In this manner the impact of the active-learning process is increased. In addition, this tool allows us to further enhance laboratory experiments already developed using a guided-inquiry approach and to design new experiments. Chemical concepts such as conformational analysis, stereochemistry, IR spectra, molecular and electronic properties, molecular orbitals, and chemical reactivity are emphasized through this approach.     

Meaningful structural descriptors from charge density

This paper provides a short introduction to the basics of electron density investigations. The two predominant approaches for the modelling and various interpretations of electron density distributions are presented. Their potential translations into chemical concepts are explained. The focus of the article lies on the deduction of chemical properties from charge density studies in some selected main group compounds. The relationship between the obtained numerical data and commonly accepted simple chemical concepts unfortunately is not always straightforward, and often the chemist relies on heuristic connections rather than rigorously defined ones. This article tries to demonstrate how charge density analyses can shed light on aspects of chemical bonding and reactivity resulting from the determined bonding situation. Sometimes this helps to identify misconceptions and sets the scene for new unconventional synthetic approaches.     

Investigating interfacial parameters with platinum single crystal electrodes

The concepts of total and free charge of platinum single crystal electrodes are revised in this paper, together with the associated concepts of potential of zero total and free charge. Total charges can be measured from CO displacement method. Results on solution of different pH are described. A novel buffer composition is used to attain pH values close to neutrality while avoiding interferences from anion adsorption processes. Stress is made on the fact that free charges are not accessible through electrochemical measurement for systems at equilibrium since adsorption processes (hydrogen and hydroxyl) interfere with free charge determination. Still, a model is described that allows, under some assumptions, extract free charge values and the corresponding potential of zero free charge for Pt(111) electrodes. On the other hand, fast measurement outside equilibrium can separate free charges from adsorption processes based on their different time constant. In this way, the laser induced temperature jump experiment allows determination of the potential of maximum entropy, a magnitude that is intimately related with the potential of zero free charge. Values of the potential of maximum entropy as a function of pH are given for the different basal planes of platinum.     

《高分子化学》教学中有机化学知识的有效利用探索

高分子化学和有机化学紧密相连,后者是学习前者的基础.在高分子化学教学中,有效利用有机化学知识解释聚合物的一些概念,将有助于学生更好的理解和掌握高分子化学知识.本文根据教学实践,介绍了几点利用有机化学知识帮助解释高分子化学中的概念或反应的实例,并对教材中存在的疑点提出了自己的看法.     

Ill‐defined chemical concepts: The problem of quantification

From time to time, ill‐defined concepts leads to never‐ending discussions in the chemical literature. “Is there a quadruple bond in the C₂ molecule? What about the boron–boron triple bond? Can we uniquely define concepts like aromaticity or bond order at all?” With this tutorial review I would like to point out that some of the contemporary publications in chemistry are characterized by a confusion of ideas and concepts, and in part ill definitions. And, that exactly those ill‐defined concepts lead to never ending controversies in the literature. Examples of well‐ and ill‐defined concepts in chemistry are discussed.     

Structured system in chemistry: comparison with mechanics and biology

The fundamental concept of structured chemical system has been introduced and analysed in this paper. This concept, as in biology but not in physics, is very important in chemistry. In fact, the main chemical concepts (molecule and compound) have been identified as systemic concepts and their use in chemical explanation can only be justified in this approach. The fundamental concept of “environment” has been considered and then the system concept in mechanics, chemistry and biology. The differences and the analogies between the use of the systemic approach in these disciplines have been analyzed and correlated to the general problem of reductionism and complexity perspectives. The inanimate–animate dichotomy can be reconsidered in this new approach. Since the chemical systemic concepts of molecule and compound can be dated to the nineteenth century, chemistry can be considered the first true systemic science and its historical evolution can be a model for other sciences (such as the humanities) where the systemic concepts are important.     

Hydrotropes

The concepts “hydrotrope” and “hydrotropy” are reviewed with a strong focus on the literature from recent years. The action and physical–chemical behavior of hydrotropes are discussed in relation to co-solubilizers and surfactants. A definition of a hydrotrope is formulated, and it is demonstrated that the unique behavior of a hydrotrope, which distinguishes this class of substances from both co-solubilizers and regular surfactants, is that the aggregation is weak without a hydrophobic solute, but there is a pronounced aggregation in the presence of a hydrophobic solute.     

Quantum tunneling of magnetization and related phenomena in molecular materials

Molecules comprising a large number of coupled paramagnetic centers are attracting much interest because they may show properties which are intermediate between those of simple paramagnets and classical bulk magnets and provide unambiguous evidence of quantum size effects in magnets. To date, two cluster families, usually referred to as Mn12 and Fe8, have been used to test theories. However, it is reasonable to predict that other classes of molecules will be discovered which have similar or superior properties. To do this it is necessary that synthetic chemists have a good understanding of the correlation between the structure and properties of the molecules, for this it is necessary that concepts such as quantum tunneling, quantum coherence, quantum oscillations are understood. The goal of this article is to review the fundamental concepts needed to understand quantum size effects in molecular magnets and to critically report what has been done in the field to date.     

The concept and rôle of charge localization in mass spectrometry

The concepts of charge localization and of radical localization are considered both with regard to their validity and to their usefulness in explaining and predicting the unimolecular fragmentation pathways for positively charged ions formed from organic compounds. It is concluded that there is experimental support for these concepts.     

Circulation of Concepts

A major obstacle to chemistry being a deductive science is that its core concepts very often are defined in a circular manner: it is impossible to explain what an acid is without reference to the complementary concept of a base. There are many such dual pairs among the core concepts of chemistry. Such circulation of concepts, rather than an infirmity chemistry is beset with, is seen as a source of vitality and dynamism.     

Foreword

The world of catalysis has grown and broadened greatly. The necessity of catalytic technology in solving the contemporary environmental and industrial problems is obvious. Catalysis will be even more important in the next century in relation to global preservation and the supply of energy and resources. What we now need are truly innovative and useful catalysts and what we lack is the methodology of how to make those catalysts. We may have to admit that, in spite of a large number of published papers, there are many mere trial-and-error type repetitions and very few new and significant findings or concepts. This is due to the very complex nature of catalysts, industrial catalysts in particular. It is not easy to find the right way to proceed. One positive step to assist in finding the right way may be to promote a close and quick exchange of information and new concepts worldwide. We now start a new journal from Japan affiliated with the Catalysis Society of Japan: Catalysis Surveys from Japan. The main aim of this new journal is to disseminate as early as possible the important findings or movements from Japan which possibly lead to new concepts for the design of useful catalysts. Rapid, invited, short reviews or accounts from academia and industry will constitute the major part of Catalysis Surveys from Japan. Surveys of recent progress and activities in catalytic science and technology and related areas in Japan will be covered regularly as well. The journal will be issued twice a year. We would appreciate it if colleagues around the world who read the articles in Catalysis Surveys from Japan would send us critical comments. If requested and deemed appropriate, the comments will be included in the journal. We will be very happy if this small, new journal stimulates global communication between scientists and engineers in the world of catalysis, and assists in the development of innovative useful catalysts.     

Foreword

The world of catalysis has grown and broadened greatly. The necessity of catalytic technology in solving the contemporary environmental and industrial problems is obvious. Catalysis will be even more important in the next century in relation to global preservation and the supply of energy and resources. What we now need are truly innovative and useful catalysts and what we lack is the methodology of how to make those catalysts. We may have to admit that, in spite of a large number of published papers, there are many mere trial-and-error type repetitions and very few new and significant findings or concepts. This is due to the very complex nature of catalysts, industrial catalysts in particular. It is not easy to find the right way to proceed. One positive step to assist in finding the right way may be to promote a close and quick exchange of information and new concepts worldwide. We now start a new journal from Japan affiliated with the Catalysis Society of Japan: Catalysis Surveys from Japan. The main aim of this new journal is to disseminate as early as possible the important findings or movements from Japan which possibly lead to new concepts for the design of useful catalysts. Rapid, invited, short reviews or accounts from academia and industry will constitute the major part of Catalysis Surveys from Japan. Surveys of recent progress and activities in catalytic science and technology and related areas in Japan will be covered regularly as well. The journal will be issued twice a year. We would appreciate it if colleagues around the world who read the articles in Catalysis Surveys from Japan would send us critical comments. If requested and deemed appropriate, the comments will be included in the journal. We will be very happy if this small, new journal stimulates global communication between scientists and engineers in the world of catalysis, and assists in the development of innovative useful catalysts.     

Causal concepts in chemical vernaculars

Though causality seems to have a natural place in chemical thought, the analysis of the underlying causal concepts requires attention to two different research styles. In Part One I attempt a classification and critical analysis of several philosophical accounts of causal concepts which appear to be very diverse. I summarize this diversity which ranges from causality as displayed in regular concomitances of types of events to causality as the activity of agents. Part Two is concerned with the analysis of contrasting chemical discourses, comparing the classical atomist style of Boyle, and Lavoisier and von Liebig with the later energeticist style of van’t Hoff and Hinshelwood. In detail different clusters of causal concepts can be abstracted from these discursive styles, yet they all approximate the Realist format for causal discourse. By way of summary I make an attempt to map the vernacular distinctions of Part Two onto the philosophical territory of Part One. The argument is rounded off with a brief analysis of a chemical publication of 2008.     

Heteroditopic receptors for ion-pair recognition

Ion-pair recognition is a new field of research emerging from cation and anion coordination chemistry. Specific types of heteroditopic receptor designs for ion pairs and the complexity of ion-pair binding are discussed to illustrate key concepts such as cooperativity. The importance of this area of research is reflected by the wide variety of potential applications of ion-pair receptors, including applications as membrane transport and salt solubilization agents and sensors.