Fingerprint region, of infrared spectrum

Fingerprint region of infrared spectrum, 519 First point of difference rule, lUPAC nomenclature, 68, 408, 859 Fischer, Emil, 271... 

It is highly unlikely that the IR spectra of two different compounds (except enantiomers) will show the same frequencies for all their various complex vibrations. For this reason, the infrared spectrum provides a fingerprint of a molecule. In fact, the region of the IR spectrum containing most of these complex vibrations (600 to 1400 cm-1) is commonly called the fingerprint region of the spectrum. 

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. 

Know the meaning of the functional group region and fingerprint region of an infrared spectrum, and tell what kind of information can be obtained from each. 

Figure 8. Fingerprint region of the attenuated total reflectance infrared spectrum of etodolac.

The evaluation involved four basic methods and variants of them. They included the standard visual overlay method, or a modification of it that involved some linear measurements in the fingerprint region of the infrared spectrum the Brown log-ratio method (26) the vector method devised by Killeen et al. (44,45) and the standard ASTM method (22). The overlay method was the best method when used by someone experienced in interpreting weathered oils. 

Tips and traps. Not all methods of characterizing a substance are equally useful in elucidating structures or in identifying samples. Consider two examples. First, the fingerprint region of an infrared spectrum may contain a... 

The conversion of oleic acid to 10-D-hydroxystearic acid by a pseudomonad has been studied in a medium enriched in DjO (Schroepfer, 1966). The reaction occurred with stereospecific incorporation of one atom of solvent hydrogen at carbon 9. The location of the deuterium was established by a combination of chemical and mass spectrometric evidence. After extraction with ether and silicic acid column chromatography, crystals were obtained of 10-D-hydroxy-[9- Hi]-stearic acid. The presence of deuterium in the compound was indicated by a 2128 cm" C—D stretching band in the infrared spectrum of the free acid and of its methyl ester. The fingerprint region of the spectra differed significantly from that of the spectra of the corresponding undeuterated compounds (Table 15.1) as has been... 

The main absorption bands of the polyethylene spectrum have been assigned to the different infrared active modes [4-6], but details, particularly in the fingerprint region of 700-600 cm, remain to be worked out because of interactions between vibrational modes. Several references [2,3,6,7,8] give details on the mathematical apparatus used to interpret the infrared spectra of polymers. 

Fingerprint region (Section 13 20) The region 1400-625 cm of an infrared spectrum This region is less character istic of functional groups than others but varies so much from one molecule to another that it can be used to deter mine whether two substances are identical or not Fischer esterification (Sections 15 8 and 19 14) Acid cat alyzed ester formation between an alcohol and a carboxylic acid... 

Figure 12.15 The four regions of the infrared spectrum single bonds to hydrogen, triple bonds, double bonds, and fingerprint.

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