Infrared spectroscopy chemical structure analysis

Gaboury, S. R. Urban, M. W. Analysis of Gas-Plasma-Modified Poly(Dimethylsiloxane) Elastomer Surfaces. Attenuated-Total-Reflectance-Fourier Transform Infrared Spectroscopy. In Structure-Property Relations in Polymers Urban, M. W., Graver, C. D., Eds. Advances in Chemistry Series 236 American Chemical Society Washington, DC, 1993 pp 777-790. 

Micro and chemical structural analysis, including porosity, bonding, coking X-ray diffraction (XRD) Nuclear magnetic resonance (NMR) Fourier-transform infrared (FTIR) Scanning electron microscopy (SEM) Transmission electron microscopy (TEM) Atomic force microscopy (AFM) Raman spectroscopy Small probe molecule volumetric and gravimetric adsorption... 

Unique applications employ both types of spectroscopies for structural analysis. The complementary nature of infrared and Raman effects can be seen in the structure determination of 1 1 hexafluoroisobutylene and vinylidene fluoride copolymer. This problem is virtually impossible to solve with other techniques. The two monomers can be linked in two ways during polymerization, by formation of head-to-tail (normal linking) or head-to-head linkages. By comparing infrared and Raman spectroscopic data, it was concluded that the polymers formed are indeed alternating in nature (66). It was additionally concluded that only head-to-tail linkages were observed. The proposed chemical structure is shown below. 

Dan and co-workers [8] studied the structures and thermal and thermo-oxidative stabilities of the gel and chlorinated natural rubber from latex. The polymers were analysed by chemical analysis, high-resolution pyrolysis-gas chromatography-mass spectroscopy (HR-Py-GC-MS) coupled with Fourier-transform infrared spectroscopy, and thermal analysis techniques [dynamic thermal analysis and thermogravimetric analysis (TGA)]. 

Infrared spectroscopy has proven to be a very informative and powerful technique for the characterization of zeolitic materials. Most infrared spectrometers measure the absorption of radiation in the mid-infrared region of the electromagnetic spectrum (4000-400 cm or 2.5-25 xm). In this region of the spectrum, absorption is due to various vibrational modes in the sample. Analysis of these vibrational absorption bands provides information about the chemical species present. This includes information about the structure of the zeolite as well as other functional... 

Flanigen, E.M. (1975) Structural analysis by infrared spectroscopy. ACS Monogr., 171, 80-117 Rabo, ). (ed.) (1975) Zeolite Chemistry and Catalysis, American Chemical Sodety, Washington, D.C. 

The wavelengths of IR absorption bands are characteristic of specific types of chemical bonds. In the past infrared had little application in protein analysis due to instrumentation and interpretation limitations. The development of Fourier transform infrared spectroscopy (FUR) makes it possible to characterize proteins using IR techniques (Surewicz et al. 1993). Several IR absorption regions are important for protein analysis. The amide I groups in proteins have a vibration absorption frequency of 1630-1670 cm. Secondary structures of proteins such as alpha(a)-helix and beta(P)-sheet have amide absorptions of 1645-1660 cm-1 and 1665-1680 cm, respectively. Random coil has absorptions in the range of 1660-1670 cm These characterization criteria come from studies of model polypeptides with known secondary structures. Thus, FTIR is useful in conformational analysis of peptides and proteins (Arrondo et al. 1993). 

The analytical utility of near-infrared spectroscopy can be demonstrated by an analysis of mixtures composed of glucose, lactate, urea, alanine, ascorbate, and triacetin in a pH 6.8 aqueous phosphate buffer.6 The chemical structures of these test compounds are presented in Figure 13.2. These components were selected to represent different classes of molecules expected in typical biological matrices. Glucose represents carbohydrates lactate represents small organic acids urea is a... 

Bonino was the first chemist in Italy at the beginning of the 1920s to perceive and to exploit the importance of infrared spectroscopy for chemistry. The infrared technique offered considerable advantages for researchers working on the composition and structure of chemical compounds. While traditional methods of analysis, such as measurements of melting point or refractive index, yield information about one particular characteristic of the compound, an infrared spectrum offers several physical indicators. Despite their importance to infrared spectroscopy, however, Bonino s papers did not lead to a strong reception along the same lines within the Italian chemical community. Italian chemists continued to use classical methods of... 

In the field of CWC-related analysis, the chemicals should be identified by comparing their spectra to spectral libraries or to spectra measured from authentic chemicals. In infrared spectroscopy of CWC-related chemicals, the spectral interpretation is not enough for unambiguous identification, but it is an important tool in the structural elucidation of unknown chemicals. 

Fourier-Transform Infrared (FTIR) spectroscopy as well as Raman spectroscopy are well established as methods for structural analysis of compounds in solution or when adsorbed to surfaces or in any other state. Analysis of the spectra provides information of qualitative as well as of quantitative nature. Very recent developments, FTIR imaging spectroscopy as well as Raman mapping spectroscopy, provide important information leading to the development of novel materials. If applied under optical near-field conditions, these new technologies combine lateral resolution down to the size of nanoparticles with the high chemical selectivity of a FTIR or Raman spectrum. These techniques now help us obtain information on molecular order and molecular orientation and conformation [1],... 

Nuclear magnetic resonance spectroscopy (NMR) is the most powerful tool available for organic structure determination. Like infrared spectroscopy, NMR can be used with a very small sample, and it does not harm the sample. The NMR spectrum provides a great deal of information about the structure of the compound, and many structures can be determined using only the NMR spectrum. More commonly, however, NMR spectroscopy is used in conjunction with other forms of spectroscopy and chemical analysis to determine the structures of complicated organic molecules. 

The elucidation and confirmation of structure should include physical and chemical information derived from applicable analyses, such as (a) elemental analysis (b) functional group analysis using spectroscopic methods (i.e., mass spectrometry, nuclear magnetic resonance) (c) molecular weight determinations (d) degradation studies (e) complex formation determinations (f) chromatographic studies methods using HPLC, GC, TLC, GLC (h) infrared spectroscopy (j) ultraviolet spectroscopy (k) stereochemistry and (1) others, such as optical rotatory dispersion (ORD) or X-ray diffraction. 

Amber is a fossilized form of terpenoid resin found in many parts of the world and used by people of many different cultures. The scientific analysis of amber began as early as the 16th century (1), and the analysis of its chemical composition has been going on for over 100 years (2). Because the material is nearly insoluble, modern analysis is primarily by infrared spectroscopy (3). Additional structural information about amber is now avail-... 

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