Rotatory dispersion infrared

The secondary and tertiary structure of a partially purified 7S globulin was examined by Fukushima (7) based on optical rotatory dispersion, infrared and ultraviolet difference spectra. Antiparallel (5 -structure (352) and random coil (60%) predominated with only 5% helical structure present. The contribution of the three structures was calculated from molecular ellipticity values obtained by circular dichroism (11) and from the Moffitt parameters in ORD (11, 12). Between 210 and 250 nm, the experimental CD curve for the 7S protein was similar to the CD curve computed from ORD Moffitt parameters with the major dissimilarity occurring at 208-213 nm. 

In addition to chemical correlations discussed above, several physical methods are now available for the determination of the relative and absolute configurations of chiral sulfur compounds. Among these, NMR, infrared (IR), optical rotatory dispersion (ORD), circular dichroism (CD), and X-ray analysis are the most important. Sections III-B-1 to III-B-5 outline applications of these techniques for establishing the chirality around the sulfur atom. 

Their characteristic optical rotatory dispersion or circular-dichroism curves, and their infrared spectra, rich in characteristic frequencies, may be useful. Paper chromatography permits preliminary identification of the glycosyl phosphate or monosaccharide resulting after degradation, and the specific enzymic reactions of these products are widely used to provide additional evidence. 

There are many more solvent effects on spectroscopic quantities, that cannot be even briefly discussed here, and more specialized works on solvent effects should be consulted. These solvent effects include effects on the line shape and particularly line width of the nuclear magnetic resonance signals and their spin-spin coupling constants, solvent effects on electron spin resonance (ESR) spectra, on circular dichroism (CD) and optical rotatory dispersion (ORD), on vibrational line shapes in both the infrared and the UV/visible spectral ranges, among others. 

For blood cell membranes the agreement of optical rotatory dispersion and infrared spectroscopy is reassuring. About one-third to one-fourth of the protons in the peptide bonds do not exchange in D20. This non-exchangeable fraction can be equated with the helical content of... 

We were also concerned about the possibility of infrared rotatory dispersion (IRD). Although this is a potential problem with any chiral crystal, the literature suggests that this effect is negligible in the infrared region of interest [62], In fact, the vanishingly small magnitude of this effect has made it very difficult to measure it directly in any system. 

Like other phenomena involving interactions between electromagnetic radiation and organic molecules, as in infrared, ultraviolet, and nmr spectroscopy, optical rotatory dispersion curves often are quite sensitive to small changes in structure. As an example, the rotatory dispersion curves for enantiomers of cis- and trcMr-lO-methyl-2-decalones, 16 and 17, are reproduced in Figure 19-7 ... 

Optical rotatory dispersion, circular dichroism, and infrared spectra of... 

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. 

The measurement of vibrational optical activity (VOA) lacks some of the severe disadvantages mentioned. Vibrational spectral bands are less likely to overlap and can be measured using two complementary techniques namely infrared and Raman spectroscopy. They can be measured as well in the crystalline as in the liquid or gaseous state, and the techniques are applicable to solutions while nearly reaching (complemented with the appropriate theoretical models) the accurateness of the X-ray method. VOA has drawbacks too the effects are quite small and tend to be obscured by artifacts. They are about 10 times weaker than the optical rotatory dispersion (ORD) and the circular dichroism (CD) in the UV-VIS range. However, this apparent disadvantage is more and more relieved by instrumental advances. 

As a first step towards the measurement of single molecule effects, Schrader and Korte (1972) reported the measurement of the infrared rotatory dispersion of carvone in liquid crystalline solution. They used a modified commercial spectrometer. They observed a huge effect which is not the result of the carvone itself but of the liquid crystal in which a helical arrangement (cholesteric state) is induced by the chiral solute (Sec. 4.6.4). In this case the liquid crystal acts as a kind of molecular amplifier which allows the absolute configuration of tiny amounts of solutes to be determined reliably. At about the same time Dudley et al., (1972) measured the infrared circular dichroism of (-)-menthol in a liquid crystal. Their equipment consisted of a normal infrared spectrometer supplemented by a Fresnel rhomb made from sodium chloride. 

Korte EH, Schrader B (1981) A new chiroptical method Infrared rotatory dispersion of induced cholesteric solutions. In Clark RJH, Hester RE (eds) Advances in infrared and Raman spectroscopy, vol 8. Heyden, London, p 226 Korte EH, Schrader B, Bualek S (1978) J Chem Res M 1978 3001 Korte EH, Staat H (1989) SPIE 1145 296 Korte EH, Staat H (1993) Fresenius J Anal Chem 347 454 Koriiim G (1969) Refiexionsspektroskopie, Springer, Berlin Kortiim G, Delfs H (1964) Spectrochim Acta 20 405 Kosloff R (1988) J Chem Phys 92 2087 Kostyk E, Welsh HL (1980) Can J Phys 58 534... 

Infrared spectrometry Rotatory dispersion early 1950 s 1955 Commercial instrument... 

For the first time in this Series, references to proton magnetic resonance (p.m.r.), infrared (i.r.), mass (m.s.), and optical rotatory dispersion (o.r.d.) spectra are included in the Tables. This has been done in recognition of the increasing role played by spectroscopy and spectrometry in the identification of derivatives of sugars. 

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