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Fingerprint region, infrared spectroscopy

The next most useful is vibrational spectroscopy but identification of large molecules is still uncertain. In the laboratory, vibrational spectroscopy in the infrared (IR) is used routinely to identify the functional groups in organic molecules but although this is important information it is not sufficient to identify the molecule. Even in the fingerprint region where the low wavenumber floppy vibrational modes of big molecules are observed, this is hardly diagnostic of structure. On occasion, however, when the vibrational transition can be resolved rotationally then the analysis of the spectrum becomes more certain. [Pg.60]

Infrared spectroscopy is an excellent tool in iminoborane chemistry, which readily permits, to distinguish between iminoboranes and nitrile-borane adducts and to identify monomeric and dimeric forms of iminoboranes. This event is due to the fact that the i>CN of CN multiple bonds absorbs outside the fingerprint region and can be considered to be a valuable group frequency even when mixed with other vibrational modes. In some cases other vibrations like NH, BH, B-halogen or B-S stretching modes are helpful for determining the structure of iminoboranes. [Pg.60]

The fingerprint region lies between 1300-400 cm-1 which is considered to be the most valuable component of the spectra and mainly comprises of a specifically large number of unassigned vibrations. Therefore, IR-spectroscopy aids in the identification of unknown compound by comparing its spectrum with a standard spectra recorded under exactly similar experimental parameters. Thus, pharmaceutical substances that exhibit the same infrared spectra may be inferred as identical. [Pg.335]

Infrared spectroscopy is mainly used to tell what types of bonds are present in a molecule (using the functional group region, 1500-5000 cm-1) and whether two substances are identical or different (using the fingerprint region, 700-1500 cm-1). [Pg.233]

Infrared spectroscopy can provide conclusive proof that two compounds are either the same or different. The peaks in the fingerprint region depend on complex vibrations involving the entire molecule, and it is highly improbable for any two compounds (except enantiomers) to have precisely the same infrared spectrum. [Pg.536]

Infrared spectroscopy can be applied to V. the characterization of polymeric materials at various levels of sophistication. As most commonly used, it is a rapid and easy method for the qualitative identification of major components through the use of group frequencies and distinctive patterns in the fingerprint region of the spectrum. Let s look at a couple of examples. [Pg.181]

We have chosen as a simple model system the situation for which R H and R >phenyl. They both separately react very fast, and form single phase products easy to identify both by infrared spectroscopy ( i p.g at 2470 cm-l phenyl C-H fingerprint in the 700-800 cm l region) and by their very different layer repeat... [Pg.231]

The use of infrared spectroscopy, either through fingerprint characterisation or by functional group identification, is well established. IR vibrational spectroscopy has thus been applied in spectroelectrochemistry for quite some time. ° The possibility to establish the symmetry of a molecule has made IR-SEC a most valuable tool for mixed-valence chemistry, ° allowing intramolecular electron-transfer rates in the picosecond region to be assessed and electron-transfer isomers to be established. ... [Pg.82]

A rapid FTIR method for the direct determination of the casein/whey ratio in milk has also been developed [26]. This method is unique because it does not require any physical separation of the casein and whey fractions, but rather makes use of the information contained in the whole spectrum to differentiate between these proteins. Proteins exhibit three characteristic absorption bands in the mid-infrared spectrum, designated as the amide I (1695-1600 cm-i), amide II (1560-1520 cm-i) and amide III (1300-1230 cm >) bands, and the positions of these bands are sensitive to protein secondary structure. From a structural viewpoint, caseins and whey proteins differ substantially, as the whey proteins are globular proteins whereas the caseins have little secondary structure. These structural differences make it possible to differentiate these proteins by FTIR spectroscopy. In addition to their different conformations, other differences between caseins and whey proteins, such as their differences in amino acid compositions and the presence of phosphate ester linkages in caseins but not whey proteins, are also reflected in their FTIR spectra. These spectroscopic differences are illustrated in Figure 15, which shows the so-called fingerprint region in the FTIR spectra of sodium caseinate and whey protein concentrate. Thus, FTIR spectroscopy can provide a means for quantitative determination of casein and whey proteins in the presence of each other. [Pg.120]

Commercial spectrometers became available in the late 1930s. World War II spurred production of improved spectrometers and development of analytical methods to solve the isomer analysis needs of the petroleum, rubber, and chemical industries. Fortunately, the rock salt prism data obtained during those productive years In the application of infrared spectroscopy to commercial products and complex mixtures are as effective in the fingerprinting region for... [Pg.711]

Quantitative infrared spectroscopy suffers certain disadvantages when compared with other analytical techniques and thus it tends to be confined to specialist applications. However, there are certain applications where it is used because it is cheaper or faster. The technique is often used for the analysis of one component of a mixture, particularly when the compounds in the mixture are alike chemically or haye very similar physical properties, e.g. structural isomers. In these cases, analysis by using ultraviolet/visible spectroscopy is difficult because the spectra of the components will be almost identical Chromatographic analysis may be of limited use because the separation of isomers, for example, is difficult to achieve. The infrared spectra of isomers are usually quite different in the fingerprint region. Another advantage of the infrared technique is that it is non-destructive and requires only a relatively small amount of sample. [Pg.85]


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Fingerprint region

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Infrared spectroscopy fingerprint

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