Infrared Spectrum Characterization

This modification method has an obvious shortcoming in that excess stearic acid remains on the whisker s surface if not removed. When filling into the polymer, the excess acid molecules will affect the property of materials. We have attempted to fill whiskers modified like this into polypropylene and found that the tensile strength of the composite material is actually lower than that of the pure polypropylene. 

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This is one of the most common analytical techniques used with plastics. The easy operation and availability of this type of equipment have contributed to its popularity. Although the infrared spectrum characterizes the entire molecule, certain groups of atoms give rise to absorption bands at or near the same frequency, regardless of the rest of the molecule s structure. The persistence of these characteristic absorption bands permits identification of specific atomic groupings within the molecular structure of a sample. 

Nevertheless, a molecule possesses sufficient vibrations so that all its frequencies taken together can be used to characterize it. In this sense the infrared spectrum is generally considered to be a molecule s fingerprint."... 

The simplicity of the infrared spectrum of solid Cgo (see Fig. 9), which shows four prominent lines at 527, 576, 1183, 1428 cm each with Ti symmetry [4], provides a convenient method for characterizing Cqq samples [4, 88]. The IR spectrum of solid Cqq remains almost unchanged relative to the isolated Ceo molecule, with the most prominent addition being the weak feature at... 

The pure, crystalline (— )-proto-quercitol (13) which was isolated had an infrared spectrum identical with that of authentic ( + )-proto-quercitol, and its optical rotation was equal and opposite. Further characterization and preparation of the racemic form, by mixing the enantiomers, is described elsewhere (30). 

The value of infrared spectra for identifying substances, for verifying purity, and for quantitative analysis rivals their usefulness in learning molecular structure. The infrared spectrum is as important as the melting point for characterizing a pure substance. Thus infrared spectroscopy has become an important addition to the many techniques used by the chemist. 

A report by Ozin et al. in 1977 describes the formation of Ti(CO)6 via matrix cocondensation techniques (11). This green complex, while not isolated, was characterized by its infrared and ultraviolet-visible spectra. In a pure CO matrix, a color change from green to reddish-brown was observed on warming from 10 K to about 40-50 K. The infrared spectrum of the reddish-brown material showed no evidence for coordinated CO, thus suggesting the extreme thermal instability of Ti(CO)6. 

US patent 6,756,381, Compositions and formulations of 9-nitrocamptothecin polymorphs and methods of use thereof [112]. This invention discloses a polymorphic form of 9-nitrocamptothecin, the polymorph being characterized as having an infrared spectrum with an absorption centered between 3625 and 3675 cm-1 and containing more than a trace of water. 

US patent 6,806,280, Polymorph of 5-[4-[2-( -methyl- (2-pyridyl)amino)ethoxy] benzyl]-thiazolidine-2,4-dione, maleic acid salt [117]. This invention discloses a polymorphic form of 5-[4-[2-(A-methyl-jV-(2-pyridyl)amino)cthoxy]benzyl]-thia-zolidine-2,4-dione, maleic acid salt. The polymorphic form is characterized by (i) an infrared spectrum containing peaks at 1763, 912, 856, and 709 cm-1 and/or... 

Methylzinc hydride was formed by the insertion of excited zinc atoms, in their 3Pi state, into the C-H bond of methane in an argon matrix.229 The MeZnH product was characterized on the basis of its infrared spectrum and determined to be a linear molecule with C v symmetry. The band at 1866.1 cm-1 is due the Zn-H stretch, while the band at 565.5 cm-1 was assigned to the Zn-C stretching vibration. Additional bands for isotopically labeled species were also reported. 

The unique appearance of an infrared spectrum has resulted in the extensive use of infrared spectrometry to characterize such materials as natural products, polymers, detergents, lubricants, fats and resins. It is of particular value to the petroleum and polymer industries, to drug manufacturers and to producers of organic chemicals. Quantitative applications include the quality control of additives in fuel and lubricant blends and to assess the extent of chemical changes in various products due to ageing and use. Non-dispersive infrared analysers are used to monitor gas streams in industrial processes and atmospheric pollution. The instruments are generally portable and robust, consisting only of a radiation source, reference and sample cells and a detector filled with the gas which is to be monitored. 

The decrease in acidity is due to the selective elimination of Bronsted acid sited characterized by the band at 3600 cm in the infrared spectrum. The authors claim that at the same time new, strongly acidic sites are formed under these conditions. 

ETEROAROMATics FURAN AND THIOPHENE. The chemical transformation of thiophene at high pressure has not been studied in detail. However, an infrared [441,445] study has placed the onset of the reaction at 16 GPa when the sample becomes yellow-orange and the C—H stretching modes involving sp carbon atoms are observed. This reaction threshold is lower than in benzene, as expected for the lower stability of thiophene. The infrared spectrum of the recovered sample differs from that of polythiophene, and the spectral characteristics indicate that it is probably amorphous. Also, the thiophene reaction is extremely sensitive to photochemical effects as reported by Shimizu and Matsunami [446]. Thiophene was observed to transform into a dark red material above 8 GPa when irradiated with 50 mW of the 514.5-nm Ar+ laser line. The reaction was not observed without irradiation. This material was hypothesized to be polythiophene because the same coloration is reported for polymeric films prepared by electrochemical methods, but no further characterization was carried out. 

Parry (344) determined the infrared spectrum of pyridine adsorbed on rj-alumina dehydrated at 450°. Characteristic differences in the 1400-1700 cm region exist in the spectra of pyridine adsorbed via hydrogen bonds, pyridinium ions, and pyridine coordinately bonded to electrophilic sites. Pyridinium ions are characterized by a strong band at 1540 cm and a very strong band at 1485-1500 cm" coordinately bonded pj ridine has a strong absorption at 1447-1460 cm". No evidence was found for the existence of Bronsted sites on the alumina surface. 

The vibrational spectrum of FCIO3 has been well characterized. The infrared spectrum was thoroughly analyzed by Lide and Mann (111) and... 

One of the main routine uses of infrared spectroscopy is identification of specific functional groups present in an unknown molecule and, as a result, further characterization of the unknown. By far the most common example involves the carbonyl group. Location of a strong band in the infrared in the vicinity of 1730cm is almost certain proof that carbonyl functionality is present. This confidence is based on the fact that the characteristic frequency (the CO stretch in this case) is isolated, that is to say, it is sufficiently far removed from the other bands in the infrared spectrum to not be confused with them. It also assumes that carbonyl groups in different chemical environments will exhibit similar characteristic... 

The infrared spectrum in the carbonyl stretching region is very useful in characterizing these complexes (Table I). Three infrared active bands are predicted 18 however, limited solubility may preclude observation of the weaker bands. Dimer formation is easily detected by the presence of characteristic bands.12... 

The infrared spectrum (especially the near-infrared) has assumed great importance in chemical and biological research because of the highly specific absorption of chemical compounds at these wavelengths. The infrared absorption of a given organic compound may be used to characterize that particular compound. The infrared spectrum of a mixture of several compounds among which there is no interaction, does not lie between the spectra of the individual compounds, but consists of a direct superposition of the spectra of the individual compounds... 

Figure 3a shows the FTIR spectra characterizing the infrared absorption of pyridine on PSM and AMM samples at room temperature. PSM has two strong absorption peaks at 1447 and 1559 cm"1, which are assigned to hydrogen-bonded pyridine. The FTIR spectrum characterizing the absorption of pyridine on AMM-1 is quite similar to that of PSM. However, when the content of AI2O3 increases to 5 or 10 wt%, some... 

The dihydride H2RusC(CO)147 has been reported, although its characterization was based entirely on an analysis of its infrared spectrum.20 In contrast, H2RuftC(CO)i6 8 has been prepared and fully characterized.15 Compound 8 can be made by acidification of the dianion [Ru6C(CO)16J2 4 with H2S04 in acetonitrile at -30°C. Cluster 8 may also be prepared via stepwise protonation from 4. Treatment of a dichloromethane solution of... 

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