Understanding Chemical Reactivity

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Latest release: March 14, 2013
Series
19
Books
New Developments in Molecular Chirality
Book 5·Dec 2012
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Molecular chirality is one of the fundamental aspects of chemistry. Chirality properties of molecules have implications in a wide variety of subjects, ranging from the basic quantum mechanical properties of simple of a few atoms to molecular optical activity, asymmetric synthesis, systems and the folding pattern of proteins. Chirality, in both the geometrical and the topological sense, has also been the subject of investigations in various branches of mathematics. In particular, new developments in a branch of topology, called knot theory, as well as in various branches of discrete mathematics, have led to a novel perspective on the topological aspects of molecular chirality. Some of the mathematical advances have already found applications to the interpretation of new concepts in theoretical chemistry and mathematical chemistry, as well as to novel synthetic approaches leading to new molecules of exceptional structural properties. Some of the new developments in molecular chirality have been truly fundamental to the theoretical understanding and to the actual practice of many aspects of chemistry. The progress in this field has been very rapid, even accelerating in recent years, and a review appears more than justified. This book offers a selection of subjects covering some of the latest developments. Our primary aim is to clarify some of the basic concepts that are the most prone to misinterpretation and to provide brief introductions to some of those subjects that are expected to have further, important contributions to our understanding of molecular properties and chemical reactivity.
Ultrafast Dynamics of Chemical Systems
Book 7·Dec 2012
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The last decade has witnessed significant advances in the ability to generate short light pulses throughout the optical spectrum. These developments have had a tremendous impact on the field of chemical dynamics. Fundamental questions concerning chemical reactions, once thought to be unaddressable, are now easily studied in real-time experiments. Ultrafast spectroscopies are currently being used to study a variety of fundamental chemical phenomena. This book focuses on some of the experimental and associated theoretical studies of reactions in clusters, liquid and solid media. Many of the advances in our understanding of the fundamental details of chemical reactivity result from the interplay of experiment and theory. This theme is present in many of the chapters, indicating the pervasiveness of a combined approach for eludicating molecular models of chemical reactions. With parallel developments in computer simulation, complex chemical sys tems are being studied at a molecular level. The discussions presented in this book recount many areas at the forefront of "ultrafast chemistry". They serve the purpose of both bringing the expert up to date with the work being done in many laboratories as well as introducing those not directly involved in this field to the diverse set of problems that can be studied. I hope that this book conveys the excitement that both I and the other authors in this volume feel about the field of ultrafast chemistry. John D. Simon 1993 1.D. Simon (ed.), Ultrafast Dynamics of Chemical Systems, vii.
Chemical Waves and Patterns
Book 10·Dec 2012
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The concept of macroscopic waves and patterns developing from chemical reaction coupling with diffusion was presented, apparently for the first time, at the Main Meeting of the Deutsche Bunsengesellschaft fur Angewandte Physikalische Chemie, held in Dresden, Germany from May 21 to 24, 1906. Robert Luther, Director of the Physical Chemistry Laboratory in Leipzig, read his paper on the discovery and analysis of propagating reaction-diffusion fronts in autocatalytic chemical reactions [1, 2]. He presented an equation for the velocity of these new waves, V = a(KDC)1/2, and asserted that they might have features in common with propagating action potentials in nerve cell axons. During the discussion period, a skeptic in the audience voiced his objections to this notion. It was none other than the great physical chemist Walther Nernst, who believed that nerve impulse propagation was far too rapid to be akin to the propagating fronts. He was also not willing to accept Luther's wave velocity equation without a derivation. Luther stood his ground, saying his equation was "a simple consequence of the corresponding differential equation. " He described several different autocatalytic reactions that exhibit propagating fronts (recommending gelling the solution to prevent convection) and even presented a demonstration: the autocatalytic permanganate oxidation of oxalate was carried out in a test tube with the image of the front projected onto a screen for the audience.
The Reaction Path in Chemistry: Current Approaches and Perspectives
Book 16·Mar 2013
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The so-called reaction path (RP) with respect to the potential energy or the Gibbs energy ("free enthalpy") is one of the most fundamental concepts in chemistry. It significantly helps to display and visualize the results of the complex microscopic processes forming a chemical reaction. This concept is an implicit component of conventional transition state theory (TST). The model of the reaction path and the TST form a qualitative framework which provides chemists with a better understanding of chemical reactions and stirs their imagination. However, an exact calculation of the RP and its neighbourhood becomes important when the RP is used as a tool for a detailed exploring of reaction mechanisms and particularly when it is used as a basis for reaction rate theories above and beyond TST. The RP is a theoretical instrument that now forms the "theoretical heart" of "direct dynamics". It is particularly useful for the interpretation of reactions in common chemical systems. A suitable definition of the RP of potential energy surfaces is necessary to ensure that the reaction theories based on it will possess sufficiently high quality. Thus, we have to consider three important fields of research: - Analysis of potential energy surfaces and the definition and best calculation of the RPs or - at least - of a number of selected and chemically interesting points on it. - The further development of concrete vers ions of reaction theory beyond TST which are applicable for common chemical systems using the RP concept.
Solvent Effects and Chemical Reactivity
Book 17·Apr 2006
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This book gathers original contributions from a selected group of distinguished researchers that are actively working in the theory and practical applications of solvent effects and chemical reactions. The importance of getting a good understanding of surrounding media effects on chemical reacting system is difficult to overestimate. Applications go from condensed phase chemistry, biochemical reactions in vitro to biological systems in vivo. Catalysis is a phenomenon produced by a particular system interacting with the reacting subsystem. The result may be an increment of the chemical rate or sometimes a decreased one. At the bottom, catalytic sources can be characterized as a special kind of surrounding medium effect. The materials involving in catalysis may range from inorganic components as in zeolites, homogenous components, enzymes, catalytic antibodies, and ceramic materials. . With the enormous progress achieved by computing technology, an increasing number of models and phenomenological approaches are being used to describe the effects of a given surrounding medium on the electronic properties of selected subsystem. A number of quantum chemical methods and programs, currently applied to calculate in vacuum systems, have been supplemented with a variety of model representations. With the increasing number of methodologies applied to this important field, it is becoming more and more difficult for non-specialist to cope with theoretical developments and extended applications. For this and other reasons, it is was deemed timely to produce a book where methodology and applications were analyzed and reviewed by leading experts in the field.
Entropy and Entropy Generation: Fundamentals and Applications
Book 18·Nov 2005
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Entropy and entropy generation play essential roles in our understanding of many diverse phenomena ranging from cosmology to biology. Their importance is manifest in areas of immediate practical interest such as the provision of global energy as well as in others of a more fundamental flavour such as the source of order and complexity in nature. They also form the basis of most modern formulations of both equilibrium and nonequilibrium thermodynamics. Today much progress is being made in our understanding of entropy and entropy generation in both fundamental aspects and application to concrete problems. The purpose of this volume is to present some of these recent and important results in a manner that not only appeals to the entropy specialist but also makes them accessible to the nonspecialist looking for an overview of the field.
This book contains fourteen contributions by leading scientists in their fields. The content covers such topics as quantum thermodynamics, nonlinear processes, gravitational and irreversible thermodynamics, the thermodynamics of Taylor dispersion, higher order transport, the mesoscopic theory of liquid crystals, simulated annealing, information and biological aspects, global energy, photovoltaics, heat and mass transport and nonlinear electrochemical systems.
Audience: This work will be of value to physicists, chemists, biologists and engineers interested in the theory and applications of entropy and its generation.
Computational Approaches to Biochemical Reactivity
Book 19·Apr 2006
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A quantitative description of the action of enzymes and other biological systems is both a challenge and a fundamental requirement for further progress in our und- standing of biochemical processes. This can help in practical design of new drugs and in the development of artificial enzymes as well as in fundamental understanding of the factors that control the activity of biological systems. Structural and biochemical st- ies have yielded major insights about the action of biological molecules and the mechanism of enzymatic reactions. However it is not entirely clear how to use this - portant information in a consistent and quantitative analysis of the factors that are - sponsible for rate acceleration in enzyme active sites. The problem is associated with the fact that reaction rates are determined by energetics (i. e. activation energies) and the available experimental methods by themselves cannot provide a correlation - tween structure and energy. Even mutations of specific active site residues, which are extremely useful, cannot tell us about the totality of the interaction between the active site and the substrate. In fact, short of inventing experiments that allow one to measure the forces in enzyme active sites it is hard to see how can one use a direct experimental approach to unambiguously correlate the structure and function of enzymes. In fact, in view of the complexity of biological systems it seems that only computers can handle the task of providing a quantitative structure-function correlation.
The Role of Rydberg States in Spectroscopy and Photochemistry: Low and High Rydberg States
Book 20·Apr 2006
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The aim of this volume is to offer a balanced overview of molecular Rydberg spectroscopy as it has developed over recent decades. Recent evolution has split Rydberg spectroscopy into two apparently distinct fields: the one concerns the low (n=3-5) Rydberg states, the other the very high (typically EMn/EM”150) Rydberg states. The former is aimed at spectral levels where Rydberg, valence-shell, and intermediate-type states interact, with a variety of photochemical consequences. The latter considers states extremely close to the ionization limit, from whereionization is possible with a very slight amount of additional energy. Recently developed techniques make it possible to produce ions in well-defined electronic, vibrational and rotational states, including states resulting from spin-orbit or Jahn-Teller splitting. It is then possible to study the structure and reactions of such state-selected ions as well as those of the corresponding neutral molecules. These techniques amount to badly needed high resolution photoelectron spectroscopy. The originality of the present volume consists in giving comparable weight to both low- and high-Rydberg spectroscopies. It aims at providing a glance at the whole of molecular Rydberg spectroscopy in one volume. This involves both theory and experiment, general aspects and treatments of individual molecules.

The contributors to this book are among the most prominent protagonists of this double field.