Vibrational general survey

In this section of the present book a general survey of characteristic vibrations in organic molecules is given. By a specific discussion of typical features of the characteristic vibrations of distinct groups and of typical classes of compounds, their inherent dependence on bond properties, symmetry, structural characteristics and their environment is demonstrated. Since infrared and Raman spectra supply complementary images of a vibration, both spectra are discussed simultaneously and combined infrared and Raman spectra are reproduced as examples. They are taken from the atlas published by Schrader (1989). 

After a short outline of the early history of infrared and Raman spectroscopy (Section 1), a general survey is given of different aspects of vibrational spectroscopy (Section 2). This survey is sufficient for readers who intend to get an impression of the fundamentals of vibrational spectroscopy. It serves as a common basis for subsequent chapters, which de.scribe special experimental features, the theory, and applicational details Section 3, Tools for infrared and Raman Spectroscopy Section 4, Vibrational spectroscopy of different classes and states of compounds Section 5, Evaluation procedures, and Section 6, Special techniques and applications. 

Closely related to conformational energy differences are barriers to single-bond rotation and to pyramidal inversion. Here the experimental data are restricted to very small systems and derive primarily from microwave spectroscopy, from vibrational spectroscopy in the far infrared and from NMR, but are generally of high quality. Comparisons with calculated quantities are provided in Table 8-3 for single-bond rotation barriers and Table 8-4 for inversion barriers. The same models considered for conformational energy differences have been surveyed here. 

The Laser Raman microprobe constitutes a physical method of microanalysis based on the vibration spectra characteristic of polyatomic structures. A focused laser beam excites the sample. The light diffused by the Raman effect is used for identification and localisation of the molecular constituents present in the sample. An optical microscope allows a survey of the interesting structures and the placing of the laser beam. The spectra obtained from fossil organic particles generally match well the corresponding IR-spectra, but the features in particular yield additional information, which will be discussed below with the given examples (Fig. 23, p. 36). 

This book intends to supply the basic information necessary to apply the methods of vibrational spectroscopy, to design experimental procedures, to perform and evaluate experiments. It does not intend to provide a market survey of the instruments which are available at present, because such information would very soon be outdated. However, the general principles of the instruments and their accessories, which remain valid, are discussed. Details concerning sample preparation and the recording of the spectra, which is the subject of introductory courses, are assumed to be known. Special procedures which are described in monographs, such as Fourier transformation or chemometric methods, are also not exhaustively described. This book has been written for graduate students as well as for experienced scientists who intend to update their knowledge. 

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