Infrared absorption shift

The hydrogen-bonding group of each polymer has been taken as equivalent to that of the parent mononrer. (The hydrogen-bonding tendency can be assigned qualitatively in the order alcohols > ethers > ketones > aldehydes > esters > hydrocarbons or setniquantitatively from infrared absorption shifts of CH rOD in a reference solvent and in the liquid of interest (7J.)... 

Sreenivasan also made qualitative investigations into the extent of hydrogen bonding associated with the template-monomer binding. Carbonyl infrared absorption shifts were measured in the absence and presence of cholesterol. There is a 15 cm shift upon cholesterol binding to acrylic acid [1721-1706 cm ], whereas a more pronounced 26 cm shift is observed for the binding of cholesterol to copper acrylate [1729-1703 cm ]. The larger shift is attributed to an enhanced interaction in the Cu acrylate-cholesterol system. 

A solubihty parameter of 24.5-24.7 MPa / [12.0-12.1 (cal/cm ) ] has been calculated for PVF using room temperature swelling data (69). The polymer lost solvent to evaporation more rapidly than free solvent alone when exposed to air. This was ascribed to reestabUshment of favorable dipole—dipole interactions within the polymer. Infrared spectral shifts for poly(methyl methacrylate) in PVF have been interpreted as evidence of favorable acid—base interactions involving the H from CHF units (70). This is consistent with the greater absorption of pyridine than methyl acetate despite a closer solubihty parameter match with methyl acetate. 

Spectral changes on adsorption are of three types appearance of inactive fundamentals (often coincident with infrared absorptions—see Table IX), shifts in Raman line positions for active vibrations, changes in relative peak intensities, and changes in half-bandwidths. The first three types of change have been reported for centrosymmetric adsorbates. 

Plutonium(IV) polymer has been examined by infrared spectroscopy (26). One of the prominent features in the infrared spectrum of the polymer is an intense band in the OH stretching region at 3400 cm 1. Upon deuteration, this band shifts to 2400 cm 1. However, it could not be positively assigned to OH vibrations in the polymer due to absorption of water by the KBr pellet. In view of the broad band observed in this same region for I, it now seems likely that the bands observed previously for Pu(IV) polymer are actually due to OH in the polymer. Indeed, we have observed a similar shift in the sharp absorption of U(0H)2S0ir upon deuteration (28). This absorption shifts from 3500 cm 1 to 2600 cm 1. 

Infrared absorption bands of S (n>2) complexes are usually of low intensity, while the Raman spectra often show intense and characteristic hnes. However, the assignments are difficult because of their complexity. The absorptions in electronic spectra are often assigned to intrahgand transitions, and it is known that the increasing length of the polysulfido chain leads to an increasing red shift of the absorption band. 

The infrared absorption frequencies of frans-3-substituted methyl acrylates gave a significant correlation with eq. (2). The value of p obtained is 75, which indicates predominance of the resonance effect. Three sets of nmr chemical shifts also were studied. All three sets gave significant correlation with eq. (2). The values of p obtained in two of the three sets were 70 and 78. Again, the resonance effect appears to predominate. 

Fusion of the two arylamino groups of a triarylmethane phthalide color former results in the formation of spirofluorene phthalides. Due to the increased planarity of this system, a bathochromic shift results leading also to color formers showing infrared absorption when developed. This was first exemplified in 1983102 by preparation of phthalide 26 as shown in Scheme... 

In some cases it is possible to differentiate between the various alkyl substituents. Primary, secondary and tertiary nitrates and nitrites all show clearly different infrared absorptions. The spectra of acid fluorides can be used to differentiate chain-end groups from pendant acid groups. Furthermore, the loss of all -OH species upon sulfur tetrafluoride exposure allows the reliable estimation of ketones, esters and lactones without the complication of hydrogen-bonding induced shifts in the spectra. Preliminary results from the use of these reactions to characterize y-ray oxidized polyethylene and polypropylene are used to illustrate the scope of the methods. 

The UV-spectra of azolides have already been discussed in the context of hydrolysis kinetics in Chapter 1. Specific infrared absorptions of azolides were mentioned there as well increased reactivity of azolides in nucleophilic reactions involving the carbonyl group is paralleled by a marked shift in the infrared absorption of the corresponding carbonyl bond toward shorter wavelength. For example, for the highly reactive N-acetyl-tetrazole this absorption is found in a frequency range (1780 cm-1) that is very unusual for amides obviously the effect is due to electron attraction by the heterocyclic sys-tem.[40] As mentioned previously in the context of hydrolysis kinetics of both imidazo-... 

Lin and Frei (133), upon loading of aqueous H2602 into TS-1 and removal of the solvent by evacuation, detected a peroxidic 0-0 stretch absorption at 837 cm-1 and a broad band at 3400 cm-1 by infrared difference spectroscopy. The former absorption shifted to 793 cm-1 when aqueous H2802 was loaded in TS-1 instead of H2602 (Fig. 18). No bands were observed at 837 or 3400 cm-1 with the same loading of H202 on silicalite-1. 

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