# Book Review Introduction to Molecular Dynamics and Chemical Kinetics. By G. D. Billing and K. V. Mikkelsen

код для вставкиСкачатьThese chapters are followed by a presentation of other methods of studying coordination compounds (Chapter 12), including IR, Raman, NMR, NQR, EPR, photoelectron spectroscopy, cyclovoltammetry, and X-ray diffraction. Chapters 13 and 14 cover the thermodynamics and reaction kinetics of coordination compounds, respectively. The last three chapters are devoted to bonding in cluster compounds, some aspects of bioinorganic chemistry, and an introduction to solid state theory. Here again the treatment of bonding in clusters and in the solid state is presented in a clear and convincing manner. In addition, the author supplies 14 appendixes that cover such topics as: the conformation of chelate rings, the VSEPR model, an introduction to group theory, the Russell-Saunders coupling scheme, ligand o group orbitals of an octahedra1 complex, Tanabe-Sugano diagrams, group theoretical aspects of band intensities, magnetic susceptibility, high temperature superconductors, and bonding between a transition metal atom and a C,R, ring. In general, as mentioned above, the presentation of the chapters dealing with bonding theory and its direct application (spectral and magnetic properties) is entirely suitable for students of inorganic chemistry. However, the title of the book is much more general, since in focussing on physical inorganic chemistry it includes other aspects in addition to bonding and related properties. There are many more physical chemistry topics addressed in the other chapters that are difficult to understand from a coordination chemistry point of view. Unfortunately, the treatment of topics not related to bonding, such as other methods of studying coordination compounds (Chapter 12), reaction kinetics of coordination compounds (Chapter 14), and some aspects of bioinorganic chemistry (Chapter 16), is not satisfactory. There are so many important physical aspects that needed to be covered in these chapters, but the treatment is too superficial and does not meet the standard set by the other, bonding related, chapters. Bonding is certainly important in coordination chemistry, but reactivity is just as important and should be treated equally thoroughly. The technical quality of the presentation is excellent, the figures are very clear, and at the end of each chapter there are suggestions for further reading, as well as a series of exercise problems. The author has filled the gap between physical and inorganic chemistry in an impressive way, and the book is highly recommended to 654 all students working in coordination chemistry. Rudi van Eldik Institut fur Anorganische Chemie der Universitat Erlangen-Nurnberg Erlangen (Germany) Introduction to Molecular Dynamics and Chemical Kinetics. By G. D. Billing and K. V. Mikkelsen. Wiley, Chichester, 1996. 104 pp., hardcover & 40.00.-ISBN 0-471-12739-6 This book is described on the back of the dustcover as “the most complete introduction available to molecular dynamics and the calculation of rate of reaction”. In their preface the authors explain where they start out from and what they aim to achieve. Whereas most standard works on physical chemistry merely sketch the basic ideas of reactive scattering and the theory of the transition state, their approach was to begin by explaining these concepts more precisely, and use this as a basis for what follows. According to the authors, the distinctive feature of this book is that it also develops the concepts of molecular dynamics and reactions in solution. With this approach, one should then be able to consider reactions in the gas phase, on surfaces, and in solution in relation to each other. In fact there is as yet no suitable textbook to explain and guide the student through the important concepts of the dynamics of elastic, inelastic, and reactive collisions, classical molecular dynamics, the theory of the transition state, and stochastic effects in solution. There are a number of excellent introductions to these individual subjects, but before the student goes into any one of these in detail it is certainly desirable to have a clear overall understanding of the many different aspects of reaction dynamics. To cover all that in a single semester is a very ambitious program (this introductory treatment is based on the authors’ course of lectures for third-year physical chemistry students), and one has to concentrate on certain essential aims. Thus, the basic concepts and purpose of each area studied must be presented concisely, and the essential foundation knowledge must be conveyed clearly and accurately, without unnecessary formal ballast. The special attraction and value of a good survey is that it should give the student an appreciation of the relative importance of the various topics, their interrelationships, and their common features. 8 VCH Verlagsge.yellschafimbH. 0-69451 Wrinheim, 1997 With these expectations in mind, we open the book and find that it consists of 16 chapters. First some important concepts of reactive scattering are introduced : interaction potentials, relative motion, and the collisional approach. Next there are several chapters on the theory of the activated complex: partition functions, transition state theory, unimolecular reactions. The authors then return to the question of time-dependence, with chapters on classical dynamics and nonadiabatic transitions. The above topics are covered in 59 pages. There is then a slightly longer section (63 pp.) on surfaces and reactions in solution (with the main emphasis on the latter): surface kinetics, chemical reactions in solution, solvent effects, models for reactions in solution, Kramers’ theory, and electron transfer. In addition each chapter contains a brief, but adequate and mostly well-chosen, list of references, and a number of exercises. There is an appendix containing integrals and functions, an explanation of the Laplacian transformation, basic aspects of the statistical mechanics of systems in equilibrium, and notes on dielectric polarization and solvation. Lastly there are some hints for solving the exercise problems. The whole book is in the style of brief lecture notes. Set up like stepping stones for exploring the various topics, and some of the essential steps are treated in the form of exercises. Unfortunately, one is seldom aware of the internal structure, and this can lead to confusion in view of the abbreviated style of presentation. An example of this is seen in the chapter on the relative motion of two colliding particles. Here the introductory section defines the total momentum and the relative velocity, and expresses the velocity vectors of the two particles in these terms. Introduction to kinetic energy then leads to a term that later turns out to be the kinetic energy of the center of mass. Only then do the authors introduce the relative positional vector and the positional vector for the mass center. From the introductory discussion of the translational momentum of a particle, by involving the total and relative momenta and differentiating with respect to time, the authors then obtain the force as a function of distance (mentioned here for the first time, with the implicit assumption that no external fields are present), and hence the equation of motion for the relative positional vector. Next the kinetic energy for the relative motion is introduced, expressed in terms of the time-variation of distance and angle. Then the authors present us with a new form by introducing, without expla- 0570-0833/97/3606-0654$17.50+ .SO10 Angew. Chem. Int. Ed. Engl. 1997, 36, N o . 6 BOOKS nation, an initial condition for this energy, with an impact parameter. This contains an expression represented by the symbol L , which is the contribution of the orbital angular momentum. The authors then derive an expression for an effective potential. This procedure is confusing. Here the most natural order should instead be as follows: First. the potential and kinetic energies are written as functions of the laboratory coordinates and velocities. A transformation to the center of mass separates its kinetic energy. Next comes a transformation to the relative position and its velocity; both are then expressed in polar coordinates and angular velocity. Formation of the (conjugated) orbital angular momentum L gives an expression of the angular velocity by L. At this point one changes to a Hamiltonian description with regard to the orbital angular movement. Conservation of L allows its description by the initial conditions; finally an effective potential is obtained. As a second example let us consider the sequence of steps in developing expressions for the effect on a chemical reaction of the fluctuating forces caused by the solvent. First the diffusion coefficient D ,is introduced by the expression for the current density for the molecular species i, J , = - C,Digradp,/R1: This is then used to derive Fick‘s first law. There then follows a section on diffusion as a random walk, without mentioning that here the transition probability is shared in equal parts with the nearest neighbors. However, the identification of the diffusion coefficient has to wait until Fick’s second law is treated in the next section. In another section Brownian motion is treated in a formal way, which makes it difficult to understand. Later. much space is devoted to the diffusion (of position and velocity) in a potential, even including a derivation of the Klein-Kramers equation for a Brownian oscillator. Both these topics are actually treated in a more easily understandable way in the first five pages of Kramers’ original paper (Physicu 1940, 7). Moreover. the authors have failed to include the extension to the case of high frictional coefficients (the Smoluchowski equation), which would have led on naturally to Fick’s second law. The figures d o not always help the reader’s understanding. In the chapter o n classical dynamics. coordinate systems for describing the motion of B-C relative to A are shown. One coordinate system has A as its origin, and the figure shows the mass centre of B-C and the relative position vector. But there is also a second coordinate system with its origin at the mass cenAngcw Chrm. Int. G I . EngI. 1991, 36, No. 6 ter of B-C, and a special notation is used to describe positions in this system. However, in this context the second system is completely unnecessary! Another figure in this chapter purports to show how the coordinates transform when the reference frame is moved from the mass center of B-C to that of A-C. The relative positions of A, B, and C should be the same in the two coordinate systems, but the figure shows two different configurations! A figure in the chapter on chemical reactions in solution intends to visualize a “Brownian particle”. This consists of a dumb-bell within a frame, and it is surrounded by concentric rings whose significance is never established. These are just a few of the many figures that convey nothing, are likely to mislead, o r are simply incorrect. The overall impression is as though, in some strange way, the book has been written in a succession of forward leaps alternating with backward steps, and it also contains many small errors. Consequently, reading through it is unnecessarily hard work. It therefore seems rather unlikely to help kindle students’ enthusiasm for microscopic reaction dynamics and chemical kinetics. Nikoluus P. Emsting, Nils Heineking Institut fur Physikalische und Theoretische Chemie der Humboldt-Universitat Berlin (Germany) Directory of Solvents. Edited by B. P . Whim and P . G . Johnson. Blackie/ Chapman and Hall, London, 1996. 612 pp., hardcover S 149.00.-ISBN 0-7514-0245-1 If one needs to choose a suitable solvent for a particular chemical reaction o r technological process from the vast range nowadays available, on the basis of objective criteria, the task of extracting the necessary chemical, physical, toxicological, and other data from the literature can often be very laborious. The handbook reviewed here should prove to be a valuable aid in such cases, especially when organic solvents are to be used in technological processes. Part 1 of the book, entitled “Solvents”, treats the more general aspects. The eight chapters (the work of nine authors altogether) discuss the criteria for making a correct choice of solvent and using it most effectively. In a short introductory chapter (“Introduction to Solvents”) P. Davison explains the classification of solvents, describes how they are manufactured, and 0 VCH Verlugsgesellschuft mbH, 0-69481 Weinheim, 1997 discusses the quantities consumed, their environmental acceptability, and their toxicity to humans. Chapter 2, “Solvent Action and Measurement”, by W. C. Aten, is mainly concerned with intermolecular solvent - solvent interactions, the Hildebrand and Hanson solubility parameters, and the solvation power, volatility, and viscosity of solvents. The next chapter, also by Aten, is entitled “Choosing a Solvent : Practical Advice”, and relates particularly to the choice of solvents or solvent mixtures for manufacturing solvent-borne and water-based paints. In Chapter 4, “Solvent Flammability and Reactivity Hazards”, R. L. Rogers explains the numerical properties such as flashpoint and explosible limits that determine the flammability of a solvent, an aspect of particular importance when dealing with large quantities, and describes the procedures that are demanded by legal regulations. In Chapter 5, “Protection of Health”, A. M. Moses describes the various health hazards that can arise in handling solvents, and the precautions for minimizing them. Aspects that receive special attention include the toxicities of particular solvents or groups of solvents, the correct preparation of safety data sheets, measures of inhalation toxicity (e.g., MAK and T R K values), and the legislation governing these matters in the European Union, the U K and the USA. Chapter 6, by I. D. Dobson, A. S. McCormick, and D. A. King, is entitled “Solvents in the Environment”. The authors describe the damaging effects of solvents on the earth’s atmosphere, such as the destruction of ozone in the stratosphere by CFCs, and the toxic effects on aquatic and terrestrial environments, which are still insufficiently studied. In Chapter 7, “Solvent Transport, Storage, Recovery and Disposal”, G. P. Howe explains the classification of solvents and the international regulations governing their transportation, storage, recovery, and disposal, and describes the most important methods that have been developed for the last two of these. In the last chapter of this part, under the title “Major Solvent Applications Overview”, J. R. Kelsey summarizes the most important technological applications of organic solvents. In Europe in 1994 the manufacturing areas that consumed the largest quantities of solvents (leaving aside their use as chemical intermediates) were, in descending order of bulk: paints of all kinds, pharmaceuticals and agrochemicals, printing inks and adhesives of all kinds, cleaning fluids, and household products. Part 2 of the handbook (“Solvent Data”) occupies the greater proportion, 0870-OS33/97/3606-06SSd 17.8Oi .SO/O 655

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