OH stretching bands

The infrared spectra of alcohols change markedly with increasing concentration. For example, at very low concentration, the infrared spectrum of te/t-butyl alcohol in carbon tetrachloride contains a single sharp band at approximately 3600 cm corresponding to the OH stretching motion. As the alcohol s concentration increases (by adding more alcohol to the sample), a second broad OH stretch band grows in at approximately 3400 cm and eventually replaces the other band. 

Both the infrared and ultraviolet spectra of pyrrolidine-2,3,5-triones (75) have been interpreted to support their existence as hydroxy-maleimides (76), and the occurrence of a strong OH stretching band in the infrared spectrum of 4-phenylpyrrolidine-2,3,5-trione has been taken as evidence that it too exists in a hydroxy form, probably 76 (R CeHg). However, the trioxo formulation is suggested by t/j the infrared spectra of jV-substituted pyrrolidine-2,3,5-triones, although an equilibrium apparently occurs depending upon the substituents and conditions. The zwitterion formulation 77 has been advanced for 4-aminopyrrolidine-2,3,5-trione. For chemical evidence... 

The long tail on the OH stretching band that extends from 3700 to 3400 cm is due to a small amount of residual water adsorbed on the surface. Hydrogen bonding interactions cause the peak to be broad. 

The evidence presented for the formation of hydrogen bonds with sulphoxides and sulphones was first reported by Barnard. Fabian and Koch, who measured the characteristic infra-red stretching frequency shifts of the S—O bond in the presence of MeOH in Simultaneously the OH stretching band of MeOH at... 

Bertie JE, Lan Z. 1996. Infrared intensities of liquids. XX The intensity of the OH stretching band of liquid water revisited, and the best current values of the optical constants of H20(I) at 25 °C between 15,000 and 1 cm . Appl Spectrosc 50 1047-1057. 

FIGURE 6.11 Shift of the OH stretching band for methanol hydrogen bonded to several bases as a function of base strength. 

The O H stretching spectra of ethanol trimers and larger clusters cannot be conformationally resolved in a slit jet expansion [65, 77, 157], VUV-IR spectra [184] are even broader, sometimes by an order of magnitude, and band maxima deviate systematically by up to +50 cm 1 from the direct absorption spectra. We note that ethanol dimers and clusters have also been postulated in dilute aqueous solution and discussed in the context of the density anomaly of water ethanol mixtures [227], Recently, we have succeeded in assigning Raman OH stretching band transitions in ethanol-water, ethanol water, and ethanol water2 near 3550, 3410, and 3430cm, respectively [228],... 

Figure 6 Comparison of the positions and areas of the H-honded OH stretching bands for the unmilled and milled samples. The triangles, the circles and the squares correspond to bands f g and h in the fitted spectra in Figure 4...

Problem 19.36 The ir OH stretching bands for the three isomeric nitrophenols in KBr pellets and in dilute CClj solution are identical for the ortho but different for meta and para isomers. Explain. ... 

Having thus obtained the relationship required, we will consider several examples of infrared spectra exhibiting double OH stretching bands. 

Fig. 1. (a) OH stretching band of OH/OH (solid line) and OH/OD (dotted line) cyclic acetic acid dimers (inset) dissolved in CC14. (b) Change of absorbance AA of OH/OH dimers measured with parallel polarization of pump and probe for different delay times between pump and probe pulse. 

For the DEAand TEA Y zeolites treated under vacuum, the OH stretching bands do not appear (see, for instance, Figure 4A). This would result from the negligible transformation into NH4+. This is also in agreement with the observation by Jacobs el al. (7) that the deamination of DEA and TEA Y zeolites does not lead to the stoichiometric formation of OH groups. 

The isomers, a- and / -PMoi204o or SiW Ojo, can also be distinguished by IR spectroscopy (65). The effects of solvent on the frequency have been reported (69). IR spectra of hydrated H3PW 2O40 include a broad OH stretching band and two OH bending bands, at 1610 and 1720 cm-1. The latter two correspond to water and protonated water, respectively (7). 

The presence of two O—H stretching bands shows that there are at least two types of OH groups on the montmorillonite. Work which will be discussed later shows that interpretation of the spectra of the OH stretching bands is more complicated than would be expected. On the simplest basis the OH bands can be separated into those due to adsorbed water and those due to surface OH groups. These species can be distinguished in cases where it is possible to scan the spectral region past 6.2 p. Adsorbed water... 

The surface OH groups can be considered as small probes sticking up from the surface. The position of the OH stretching band of surface OH groups is affected by the presence of adsorbed molecules. Thus, a study of the surface OH band position provides evidence on the nature of the adsorption process even though the spectrum of the adsorbed molecule is not observed. This interesting effect was first reported by Yaroslavskii and Terenin (41) and by Kurbatov and Neuimin (42). 

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