Infrared frequencies, characteristic

The discovery and identification of buckminsterfullerene, Cgo [121], was one of the most talked-about developments in chemistry in the latter part of the twentieth century, although it has been eclipsed in applications by carbon nanotubes and, more recently, graphene. The discovery was largely fortuitous, as the experiments were intended to shed light on the formation of long chains of carbon atoms, which account for much of the carbon observed in inter-stellar space. It eventually resulted in the award of a Nobel Prize to microwave spectroscopists - for a molecule without a dipole moment Identifying chemical species in space is normally done by observation of their rotational spectra (Section 7.5.1), so confirmation of the existence of fullerenes in inter-stellar dust clouds took a long time, eventually achieved by observation of four infrared frequencies characteristic of Ceo, as well as several that correspond to C70 [122],... 

Infrared frequencies are characteristic for certain bonds in molecules and they can often be used to identify chemisorbed species on surfaces. The infrared spectrum of CO or NO can sometimes also be used to recognize sites on the surface of a catalyst, as the following example shows. 

Many characteristic molecular vibrations occur at frequencies in the infrared portion of the electromagnetic spectrum. We routinely analyze polymers by measuring the infrared frequencies that are absorbed by these molecular vibrations. Given a suitable calibration method we can obtain both qualitative and quantitative information regarding copolymer composition from an infrared spectrum. We can often identify unknown polymers by comparing their infrared spectra with electronic libraries containing spectra of known materials. 

D. Lien-Vien, N. B. Colthup, W. G. Fatley, and J. G. Grasseli, The Handbook of Infrared andRaman Characteristic Frequencies of Organic Molecules, Academic Press, New York (1991). 

A relation between heats of formation of inorganic halides and characteristic infrared frequencies (v) of the solids has been claimed (156) ... 

Poly(acrylic acid) (PAA), a MIP film candidate, has been shown to bind to the bare CdSe surface from methanol solution with considerable affinity [13]. Placement of drops of a PAA-methanol solution on the surface of CdSe and evaporation of the solvent leaves a PAA film on the semiconductor surface. Once coated with this PAA film, CdSe shows no change in PL intensity in the presence of amines. Despite the lack of a PL change, the deprotonation of the carboxylic acid could be observed by the shifting of the infrared (IR) carboxylic acid peak to lower frequencies characteristic of the carboxylate anion upon amine binding, as shown in Fig. 5. The reaction chemistry is ... 

Table 21. Characteristic infrared frequencies (in cm-1) of the rare earth oxides...

Table 3.4 Characteristic olefin infrared frequencies for EPDM ...

Certain bonds and functional groups absorb infrared frequencies of a characteristic wavenumber for example ... 

Table 1. Characteristic infrared frequencies of complexes of HF and DF with different bases. From M. Couzi, J. Le Calve, P. V. Huong and J. Lascombe, J. Mol. Struct. 5, 363 (1970). Reproduced by permission from the Elsevier Scientific Publishing Company.

Table 13.3 lists infrared absorption frequencies characteristic of various groups. We shall look more closely at the infrared spectra of hydrocarbons in Sec. 13.15 and, in following chapters, at the infrared spectra of other families of compounds. 

A typical application area of expert systems and their supporting technologies is spectroscopy. Since spectra require interpretation, they are ideally suited for automated analysis with or without the aid of a spectroscopist. Particularly vibrational spectra, like infrared spectra, are subject to interpretation with rules and experience. A series of monographs and correlation tables exist for the interpretation of vibrational spectra [7-10]. The relationship between frequency characteristics and structural features is rather complicated, and the number of known correlations between... 

In addition, the infrared contributions of the side chains of the amino acids which constitute the protein must be considered. Amino acid side chains exhibit infrared modes that are often useful for investigating the local group in a protein. It is also important to be aware of the location of such modes as they may be confused with amide vibrations. Fortunately, these contributions have been found to be small in D2O when compared to the contributions made by the amide I band. The characteristic side-chain infrared frequencies of amino acids are summarised in Table 6.2b. 

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