# Book Review pH and Buffer Theory Ч A New Approach. (Series Solution Chemistry Vol. 1.) By H

код для вставкиСкачатьBOOKS ed images, spectra can be compressed, stretched, or edited in other ways, and so on. By using the hypertext transfer protocol (HTTP), documents from any computer can be loaded onto the Internet, regardless of the operating system that they use or the computer platform. The only requirement for all these operations is that the client browser’s plug-in is capable of recognizing the standardized data structure of the application concerned. The first Electronic Conference on Trends in Organic Chemistry, ECTOC 1, was organized by one of the pioneers in the field of standardization of chemical information, Henry S. Rzepa of Imperial College, London, together with his colleague Christopher Leach, and Jonathan M. Goodman (Department of Chemistry, Cambridge University), and is published in a CD-ROM version by the Royal Society of Chemistry. The conference proceedings consist of six “keynote papers” and 71 articles, which present recent results (up to mid1995) in the areas of synthetic, mechanistic, and biological chemistry. The authors are from 13 countries. On reading the keynote papers one immediately appreciates the advantages of the HTML format. A mouse-click on one of the two-dimensional valence bond formulas that are displayed brings up a three-dimensional image of the molecule that can be rotated at will, an extremely useful facility for complicated structures. These 3D structures are filed as Cartesian coordinates in the format of the Brookhaven Protein Database (*.pdb files). Taking as an example the contribution “A New Synthetic Route to the Illudin and Pterosin Family of Sesquiterpenes”, by Albert Padwa, Erin A. Curtis, and Vincent P. Sandanayaka (Department of Chemistry, Emory University, Atlanta), the key structure can be viewed from any direction and in many different representations (wire model, stick model, stickand-ball model, space-filling model, etc.) . The coordinates (from an X-ray crystallographic analysis) on which this is based are those of a precursor of illudin, which already has all the five benzene ring substituents of the later products, with the correct regiochemistry. Moreover, a novel feature of the HTTP approach is that one can then go on from this 3D presentation to edit the data. Once the coordinates from the X-ray data have been stored locally on the hard disk of one’s PC, the way is clear for further data processing such as energy calculations. In the contribution “Studying Perturbation Theory with Explorer EyeChem and VRML”, by Guillermo A. Suner, 1354 ,G Omer Casher, and Henry S. Rzepa, the imaging of structures is taken a step further. These authors have translated the semiempirical (AMI) calculated transition state structures for a large number of Diels-Alder reactions into the VRML format (virtual reality modeling language). This allows one to move around in the virtual space of the calculated structures and study the overlapping of the frontier orbitals. This technique opens up new perspectives, in the truest sense of the word, and has great possibilities for use in teaching. Most of the other contributions use only HTML text and graphics in the GIF format. They range over many different areas of organic chemistry, from new syntheses of natural products and enantioselective catalytic reactions, via the chemistry of fullerenes (where, incidentally, pdb coordinates would have been ideal), to new nonlinear optical materials and to purely theoretical studies. The work includes a full list of contributions to the discussions of the individual presentations and a list of participants (with photographs in some cases), making altogether a very successful CD-ROM. Within the next five years we may witness the disappearance of the conventional printed “book of abstracts”. Jorg Grunenberg Institut fur Organische Chemie der Technischen Universitat Braunschweig (Germany) pH and Buffer Theory - A New Approach. (Series: Solution Chemistry, Vol. 1.) By H . Riibe. John Wiley & Sons, Chichester, 1996. 192 pp., hardcover E 40.00.-ISBN 0-47196735-1 This subject has traditionally been a favorite area of research for Scandinavian chemists, and H. Rilbe is on familiar ground in this book. The author’s claim to present a “new approach” refers essentially to a general procedure for treating all types of problems in this field. According to this, all the quantities that occur in pH and buffer theory, such as concentrations and equilibrium constants, are converted into dimensionless logarithmic numbers, so as to benefit from the well-known mathematical simplifications associated with the use of logarithmic relationships. Despite this, however, as the arguments are developed in greater depth the equations quickly become very complicated. Consequently the author’s presentation comes over as rather dry and leaden on the whole, although that is partly due to VCH Verlagsgesel1.schaftmbH, 0.69451 Weinheim, 1997 the nature of the subject. Another disadvantage of the author’s new approach is that, because of the special expressions that are used, one cannot simply begin reading at a chosen place in a chapter or section of interest; instead one must first search back in the book to work out the definitions. Many of the results have been published before by the author in specialist journals, and thus the book is a summary and consolidation of that work. Chapter 1 begins by introducing the concepts of pH and the relevant equilibrium constants. For each of the aspects that are treated from a stoichiometric standpoint the author then goes on to discuss the thermodynamic relationships involved. Buffer solutions consisting of a single-proton weak acid combined with a strong base, or a weak base with a strong acid, are considered next. Here the reader meets the difficulty already mentioned above, as one needs to be familiar with the author’s definitions in order to fully understand the curves that are shown. Chapter 2 deals with two-proton protolytes and their salts with strong acids and bases. Here the ionic strength of buffer solutions is also considered. In Chapter 3 the author guides the reader through the Scylla and Charybdis of mixtures of weak acids and weak bases, offering first an approximate solution to the problem and then a more rigorous analysis. Here, as in the other chapters, he mentions alternative approaches used by other authors and considers the strengths and weaknesses of the different methods. Chapter 4 treats acids with three or more protons and their salts. Special attention is devoted to the differences between the K-values and how these affect the buffer properties. The main topic of Chapter 5 is the Debye-Huckel theory for strong electrolytes and its application to the calculation of activity coefficients. Chapter 6 is entirely devoted to the buffer properties of water and the associated titration curves. This is followed by a chapter on experimental methods for determining pK- and ApK-values and isoprotic (or isoelectric) points. Finally there is an appendix containing some computer programs for determining isoprotic points. This book, written by a well-recognized expert in the field, is intended for the specialist rather than for the student, as indicated by the absence of exercise problems, and not least by its price. It takes up from the point where the usual introductions to quantitative analysis leave off, and assumes that one is already familiar with ordinary buffer theory. The question of whether one can begin to accept the nota- 057o-0X3319713612-I354 $ 17.50+ .SO10 Angeu.. Cizrm. Inr. Ed. Engl. 1997, 36, N o 12 BOOKS tion used in the book is for the reader to decide. It remains to be seen to what extent the proposed new approach will be taken up in research and teaching. Bernhard Neumiiller Fachbereich Chemie der Universitat Marburg (Germany) Introduction to Theoretical Organic Chemistry and Molecular Modeling. By W B. Smith. VCH Publishers, New York, 1996. 192 pp., hardcover DM 89.00.--ISBN 1-56081-937-5 Computer programs for quantumchemical calculations are becoming increasingly user-friendly, and consequently chemists with limited theoretical knowledge are using them more and more often. It is all too easy for non-theoreticians to be misled by the suggestive power of the attractive graphics. so that they overvalue the information content of the results that the black box turns out with so little effort. For these users there are only three possible ways out of this dilemma: 1. leave well alone; 2. work in collaboration with colleagues; or 3. acquire the necessary theoretical knowledge by private study. This book by W. B. Smith is intended to help with the third alternative. It is certainly a welcome development when an attempt IS made to present theoretical organic chemistry at such a level that it can be understood by most nonspecialists. Although there are many excellent books on the quantum-mechanical fundamentals of chemistry, few of these offer help in the practical application of theoretical methods. In accordance with the title of this book, the author’s idea is first to introduce the reader to the theoretical fundamentals of quantum chemistry (qualitative MO theory), then in the second part (from Chapter 7 onward) to treat the most commonly used theoretical methods, and this approach is undoubtedly correct. However, it must be said at the outset that neither the first nor the second part is suitable as a student textbook. The choice of subject matter and the strong emphasis placed on the Huckel theory give cause for concern. It is true that in a treatment of such a complex topic as this within a mere Angebv. Clwn. hi.Ed EngI. 1997, 36, No. 12 192 pages, one has to be prepared to accept some compromises. Nevertheless, the mathematical derivations must be errorfree, understandable, and entirely consistent. This book contains so many errors, loose and careless statements, and lapses from rigor in the physical arguments, that a newcomer to the subject is at risk of failing to follow the discussion o r getting an incomplete picture. A few examples will illustrate this. The first is the derivation of the Schrodinger equation in a few steps on pages 2 and 3. The transition from classical mechanics to quantum mechanics is made, without further explanation, by replacing the momentum in the classical expression for the total energy by the corresponding quantum-mechanical operator, then multiplying the expression by a wave function which appears from nowhere. Arguments of this kind d o not help towards an understanding of the quantum theory. The symbols used for variables are not always consistent. On page 3 the symbol \i/ is used for the total wave-function, whereas on page 4 it represents the basis orbitals. Later we find that Y is used for molecular orbitals, whereas in the description of the S C F methods (p. 109) Y represents the total wave-function and \i/ a molecular orbital. As the text contains no mention of the changes in meaning, the reader unfamiliar with the theory will inevitably be confused. In the mathematical formulas, vectors are never clearly distinguished as such, and operators and matrices only occasionally. The lack of care in the text also appears in statements that are difficult to understand or even misleading. On page 30 alone we find that a summation index is missing from each of the equations (2.17) to (2.22), a bracket is missing in the example of butadiene, and in Equation (2.22) the indices on the two sides of the equation d o not agree. Often the symbols in the figures and equations d o not correspond to those in the text; for example, on pages 32 and 33 the coefficients are denoted by ‘a’ in the figure but by a in the text, and on page 95 the symbol for the basis orbitals is 4 in Equation (6.23) but cp in the text immediately below. On page 119 the method described here for minimizing the energy has little to d o with the Newton-Raphson method to which the author refers. Also the general discussion about mathematical methods C; VCH Verla~gesrllsrhafimbH, D-69451 Weinheim, 1997 for energy minimization is scarcely understandable and will convey little to the reader. The explanation of CISD in Section 7.4 is simply incorrect. “CI-singles,doubles” is not, as stated here, a linear combination of the ground state Slater determinants and the first and second excited states. There are also many mistakes in the non-mathematical part of the book. In Chapter 6 (pericyclic reactions, etc.) even the first reaction equation (6.1) defining pericyclic reactions is incorrect. In the Claisen rearrangement shown here, allylphenyl ether rearranges to give o-hydroxystyrene. In Equation (6.2) the second reaction arrow has below it nv instead of hv, and hv is missing from Equation (6.3). The claim that “. . . no stable ring systems containing an odd number of changes in fi can exist . . .” is presumably a guess. Again, it is incorrect and misleading to state (on page 91) that for a qualitative treatment of the stereochemistry of photochemical reactions it is unimportant whether a singlet or a triplet state is present. The list of errors and examples of slipshod writing could be continued. The poor quality of the figures is evident even on first opening the book (the Mobius strip on p. 88 and the energy hypersurface on p. 150 are two interesting examples). Leaving aside esthetic considerations, many of the figures are not very suitable for explaining the matters to which they relate. For example, the connection between the orbital diagram (6.20) and the reaction equation (6.18) would only be apparent to a specialist. Due to the large number of mistakes and examples of careless writing, the absence of any indications as to the previous knowledge assumed, and the disjointed and unclear style in which the arguments are presented, the reader unfamiliar with the subject is unlikely to learn much from the book. Moreover, the price seems unjustifiably high for a textbook of 192 pages. Perhaps the printing error on the first page-“testbook” in place of textbook-is no ordinary mistake but a Freudian slip. Raiizer Herges Institut fur Organische Chemie der Technischen Universitlt Braunschweig (Germany) 0570-0833/97/3612-13553 I7.50f .50;0 1355

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