Theoretical and physical principles of organic reactivity

Theoretical and physical principles of organic reactivity

THEO CHEM ELSEVIER Journal of Molecular Structure (Theochem) 389 (1997) 199-200 Book Reviews Theoretical and Physical Principles of Organic Reactiv...

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THEO CHEM ELSEVIER

Journal of Molecular Structure (Theochem) 389 (1997) 199-200

Book Reviews

Theoretical and Physical Principles of Organic Reactivity by Addy Press. The author has set himself the goal of presenting a more unified approach to the problem of organic reactivity and has done so quite admirably. The unifying theme is the ability of curve-crossing diagrams to provide a means to understand how perturbations in the property of one or more reactants can influence the thermodynamics and kinetics of a wide range of reactions. The text is divided into three sections. Part A establishes the basic theoretical principles of quantum mechanics, i.e. molecular orbital and valence bond theory. The author assumes no prior knowledge and builds up the concepts gradually, gracefully, and with numerous examples. Mathematics is held to a minimum, focusing instead on the qualitative and visual aspects of orbital overlap, configuration energies, and reaction coordinates. The correspondence between molecular orbital and valence bond frameworks is established early. The discussion of the former is probably more extensive than is warranted since the book makes much greater use of valence bond concepts. It is likely that the student will have already made acquaintance with most of the ideas presented here in an earlier course in undergraduate physical chemistry, in which case this section can be glossed over. The theoretical principles section is capped off with a development of the use of valence bond configurations to set up reaction profiles. It is the latter idea which comprises the unifying theme of this text, and is its principal strength. The curvecrossing model is used time and again to illustrate a number of notions of physical organic chemistry that might at first seem disparate. And it is the establishment of this model as a common language

that makes this text particularly well-suited to its target population of advanced undergraduates and graduate students who are learning about physical organic chemistry for the first time. The second section of the text describes some of the central tenets of physical and physical organic chemistry. Some of these ideas will represent a repetition of earlier material in the student’s background, such as the Arrhenius equation and the fundamentals of transition state theory. But again, it is useful to have all of the concepts in one place and those that have been studied earlier can be skipped. The author goes on to provide an easily understood presentation of the Hammond postulate, the Bell-Evans-Polanyi principle, and Marcus theory. These ideas set the stage for the introduction of linear free energy relationships, most notably the Hammet equation and the Bronsted parameter. Along with the formalization of the ideas of ionization potentials, electron affinities, and singlet-triplet separations, the author goes on to show how the common thread of curve-crossing diagrams can be used to understand all of them. A chapter is included which introduces the reader to the complicating effects of solvation in a way that a novice would not feel overwhelmed, but rather would come to believe that these issues can be addressed in a systematic fashion. Having set up this panoply of tools in the first 220 pages, the remaining 70 pages comprising the third section go on to apply the principles to several broad reactions in organic chemistry, notably nucleophilic/electrophilic reactions and radical and pericyclic reactivity. Having come along this far, the reader will find the specifics surprisingly understandable. The author makes clear distinctions between electron transfer and electron shift reactions, and extends this idea to inner-sphere and

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Book Reviews/Journal of Molecular

Structure (Theochem) 389 (1997) 199-200

outer-sphere electron transfer. This “minor” distinction permits the reader to see how many reactions can be placed along this broad spectrum, and thereby understood by similar principles, The last chapter, on pericyclic reactivity, includes an intriguing attempt to reconcile the molecular orbital ideas of the Woodward-Hoffmann rules with valence bond notions. For these purposes, the author makes use of a formalism in which the reactants and products can be thought of as a conceptual mixture of various spin states and chargetransfer complexes, Any shortcomings of this method notwithstanding, the student will be benefited by the systematic nature of the approach and the talent of the author in placing much of organic reactivity into a common framework. This text offers the novice an outstanding introduction to physical organic chemistry. As such, it is highly recommended as a text in a formal course, but it can equally serve as independent reading material for a talented undergraduate. (One weakness of this book as a class text is the absence of problems or ideas for independent reading.) The book can also be recommended to more seasoned workers in the field as a quick introduction to the potential usefulness of curve-crossing diagrams as an aid to understanding their own reactions. The junior reader will likely become enthusiastic to apply the principles introduced here to understanding of the original literature or to an independent research project. The text is remarkably free of distracting errors. The figures and tables integrate themselves nicely into the flow of the material and include an appropriate amount of content. Steve Scheiner Southern Illinois University Carbondale, IL, USA

Introduction to Molecular Dynamics and Chemical Kinetics, Gert D. Billing and Kurt V. Mikkelsen, John Wiley, New York, 1996. This book is intended for an introductory course on molecular reaction dynamics at a level that can be approached by advanced undergraduates. It seems very well suited for that purpose. I can also recommend it as a supplement to traditional

physical chemistry texts targeted at junior/senior level courses. Using this text, students are likely to reach a level where they are ready to read and make use of a good deal of contemporary research articles on dynamics and kinetics. Perhaps the best overall characterization of this text is that it is friendly and direct, something many undergraduate students surely will notice and appreciate. This also means that the volume can serve as a quick introduction for researchers whose interests are outside the subject area. The text is short and engaging. There are 16 chapters that average just two sections and less than 10 pages each. The writing, style, and notation are clear and easy to follow. The figures are drawn with a nice simplicity that makes them quite effective for illustrating the points in the discussion and in the derivations. The first five chapters explain ideas and concepts related to potential energy surfaces, trajectories on surfaces, the mechanics of collisions, cross sections, and partition functions. It does not seem the intent to develop these as full-blown topics but rather to provide only the crucial background information for reaction dynamics. The authors have been judicious in paring down a lot of subject material in order to maintain a clear focus in this introductory segment. Transition state theory is discussed in the next two chapters followed by a chapter on unimolecular reactions. There is further development of classical mechanics of collisions and then a nice overview of non-adiabaticity. Several chapters are devoted to surface and solution reactions, and these are about the most in-depth of the volume. These chapters do the most to make this a unique and valuable text. The very last chapter is on electron transfer in solution and on Marcus theory. Although offered as an introduction to the subject material, some familiarity with physical chemistry is required. For instance, by the end of only the fourth page, the energy levels of an anharmonic oscillator have entered the discussion, albeit briefly. There are a handful of problems at the end of each chapter, and the solutions to the problems given at the end of the text should prove quite helpful to students. Clifford E. Dykstra Indiana University-Purdue

University Indianapolis Indianapolis, IN, USA