Choice of examples

Although the set of examples presented are unlikely to be directly related to the systems of immediate interest to the reader, it is hoped that the discussion will highlight the methodologies commonly applied, the various approaches that can be used to solve similar problems, as well as some of the difficulties encountered and the strategies used to surmount them. Above all, it is hoped that these case studies will provide both inspiration and guidance to readers in the design of their own experiments and in the interpretation of their results. 

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Except in the case of reactions that have been known for a long time under shared names, we often took the liberty to include in the title, as well as in the references (here to save space), only the name of the major author for this we apologize to the co-authors, whose contributions are often seminal. For reactions named after contemporary authors, we have tried to consult the authors about choice of examples, etc. This led for instance to the Mannich-Eschenmoser methylination. 

The aza-Wittig reaction offers several strategies for the syntheses of heterocyclic compounds, and in Section VI a broad choice of examples is presented. Aza-Wittig reactions can be divided into an intramolecular and an intermolecular variant, the former starting with a molecule 49 (Scheme 26) that contains both an iminophosphorane group and a carbonyl function in a geometrically favorable orientation. 

An attempt has been made to apply the Cohen and Reiss theory to dimer and hydrate formation in RNA.158 The results were inconclusive, probably because of a poor choice of example. Application of the theory to RNA was complicated by the necessity of estimating the distribution of uracil residues on the chain. The results are made still more tentative by the fact that Tanaka ignored the probability of dimer formation between cytosine residues, mixed dimers between cytosine and uracil, and hydrate formation in cytosine as well as the resultant deamination phenomena. A better choice of example would have been poly-uridylic acid. 

In this chapter we consider theories of scattering by particles that are either inhomogeneous, anisotropic, or nonspherical. No attempt will be made to be comprehensive our choice of examples is guided solely by personal taste. First we consider a special example of inhomogeneity, a layered sphere. Then we briefly discuss anisotropic spheres, including an exactly soluble problem. Isotropic optically active particles, ones with mirror asymmetry, are then considered. Cylindrical particles are not uncommon in nature—spider webs, viruses, various fibers—and we therefore devote considerable space to scattering by a right circular cylinder. 

The data used in this comparison are shown in Table 9. The choice of examples in Table 9 is dictated by the practicality of collecting common cases and does not necessarily represent the results that might be obtained with the best member of any given activator class. The corrections made in order to correlate the diverse data are ... 

The goal of this chapter is more to describe general approaches to ion radical syntheses, the general synthetic methodology, than to provide a detailed account of each reaction. The choice of examples was aimed at illustrating the usefulness of ion radical syntheses. 

Since the Tanabe-Sugano diagrams for d5-systems are symmetric with respect to octahedral and tetrahedral complexes, one can strictly speaking only determine the numerical value A. However, the choice of examples in Table 3 clearly demonstrates that the manganese (II) aqua ion is Mn(H20)g++ and not Mn(HaO)4++. 

We shall aim to illustrate the diversity of chemical types in the choice of examples that will be given in subsequent sections. Clearly the structures are strongly influenced by the coordination preferences of the metals as well as by the variety of ways in which different ligands can coordinate to metals. 

The courses which M. Rouelle has given at Paris for about twenty years, are, even in the opinion of strangers, among the best of this kind. The order in which particular objects are presented, the abundance and choice of examples, the care and exactitude with which operations are performed, the origin of and relation between the phenomena observed, the new luminous, broad insights suggested ... 

I have been selective in my choice of examples of application and apologise to those whose work I may have omitted either because it did not fall into the categories of compounds I have chosen or because it slipped by me in the huge number of papers on this topic being published. I have tried to include at least some examples of work from most of the large groups in this field. I hope that some of the omissions will be remedied in the next review in this series. 

Due to these restrictions mechanistic investigation of the cleavage of cyclopropanes as well as preparation of cyclopropane derivatives (see Chapter 7) will not be discussed here. Obviously the author s personal view regarding synthetic utility could not entirely be excluded and may have influenced the choice of examples presented. 

At first the rules concentrated on product momenta. Recently it has become clear that the ability of the metastable complex to excite product angular momentum channels can also be important. There is a growing body of information, not discussed in this paper, on the propensity for intramolecular V-V transfer to govern relaxation rates. The goal of these studies, then, is to isolate as much as possible the effects of the intramolecular potential, vibrational symmetry and product channel availability on the overall rates. Maturally, all of these effects are correlated with each other. By judicious choice of examples, however, the relative importance of individual effects can be demonstrated. 

Ballhausen s latest book [30], Molecular Electronic Structures of Transition Metal Complexes appeared in 1979, 25 years after his first article. It can be seen as his answer to the question What is a molecule - in particular a transition metal complex He starts with his conclusion from a series of articles on the chemical bond [31], Chemistry is one huge manifestation of quantum mechanics . He then introduces the Bom-Oppenheimer approximation as the basis for applying electronic and nuclear coordinates, and lets the picture of a molecule unfold itself with the concepts of electronic states, potential surfaces, transitions, vibronic couplings, etc. The presentation is traditional, but contains many refinings in the discussion of a molecule s ground state as well as its excited states. The world of transition metal complexes is favoured through the choice of examples. 

The method of single-photon counting has been applied to measure lifetimes in a lai e number of different systems. An example of its application, the measurement of the subnanosecond decay of Rhodamine B, is provided by Koester and Dowben [54]. The choice of examples to illustrate these techniques is somewhat arbitrary however, this study was chosen since the experimental system constructed by these authors fairly well describes the state of the jurt. Their system utilized a cavity dumped synchronously pumped tunable dye laser producing 35 ps pulses at... 

Since the invention of polarography in 1922, more than 30,000 papers dealing with this technique have been published. Since more than 90% of those papers deal with practical applications, any choice of examples cannot be more than an indication of the possibilities the method offers. The following selection, which is necessarily subjective, was made with the aim of showing applications in a variety of fields. 

It is hoped that the present choice of examples provides a broad view perspective of quantitative mass spectrometry and successfully emphasizes that this is truly an extremely powerful and versatile interdisciplinary technology. Two books relevant to this chapter deal with trace analysis techniques applied to environmental samples (Loconto 2005) and the use of mass spectrometry in drug metabolism studies (Korfmacher 2004). 

The rest of this chapter is not intended to be a comprehensive survey of reactions involving solid supports and supported catalysts but rather to demonstrate the diverse nature of the applications of such catalysts. The choice of examples has been made to illustrate the wide range of chemical applications, rather than purely industrial processes. 

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