Hydroxyl stretching

An aerosil sample was methoxylated at 400 C to examine the effect of surface composition on the infrared spectrum. The difference spectrum between the methoxylated silica and the dried silica is shown in Figure 2b. Comparing this with the difference spectrum for hydroxylated silica (2a) several changes are apparent. First, the band due to the hydroxyl stretches at 3744 cm is diminished and replaced by bands at 2958 and 2856 cm" due to the asymmetric and symmetric CH stretching modes of the adsorbed methoxy. 

K. J. Gaffney, Paul H. Davis, I. R. Piletic, N. E. Levinger, and M. D. Fayer, Hydrogen bond dissociation and reformation in methanol oligomers following hydroxyl stretch relaxation. J. Phys. Chem. A 106, 12012 12023 (2002). 

Infrared spectra. An FT infrared spectrum of HTE liquid polymer (fan -500) is shown in Figure 2. All spectra of HTE polymers show characteristic absorptions a broad band at 3530 cm-1- for the hydroxyl stretching, three bands at 2958, 2913, and 2875 cm-1 assigned to the carbon-hydrogen stretching, an extremely strong... 

To check the completion of the reaction depicted in Scheme 12.9, single bead FTIR seemed quite conclusive because the IR band from the starting material (alcohol) has converted to the product carbonate band (Fig. 12.13). The hydroxyl stretch disappeared completely in the FTIR data. However, the possible presence of a trace amount of hydroxyl groups might not be evident in the IR spectrum. The fluorescent dye 9-anthroylnitrile reacted with resin-bound alcohol and it was very sensitive in detecting trace amount of hydroxyl groups [19]. It was used to detect the residual resin-bound alcohol and to confirm the reaction completion. 

An intense band due to the bulk hydroxyl stretch is observed at 3140 cm . Two far less intense bands at 3660 and 3484 cm can be attributed to the surface hydroxyl groups. In general, these bands can only be detected on an evacuated surface. The most reasonable assignment for these bands appears to be that of Russell et al. (1974) who found that the band at 3660 cm disappeared completely when the surface was phosphated and so attributed it to the singly coordinated OH groups the band at 3484 cm was not replaceable by adsorbed phosphate and was considered to consist of contributions from the doubly and triply coordinated OH groups. 

Briggs, L. and Colebrook, L., Infrared spectra of flavanones and flavones. Carbonyl and hydroxyl stretching and CH out-of-plane bending absorption, Spectrochim. Acta, 18, 939, 1962. 

THE TUNNELLING OF THE PROTONS AS A CAUSE OF THE SPLITTING OF HYDROXYL STRETCHING BANDS... 

Figure 7.9. IR spectra taken from a single bead at various times in reaction 11. Spectra were taken from a single flattened bead at 0, 20, 60, and 240 min after the initiation of the oxidation reaction. The hydrogen-bonded and unbonded hydroxyl stretch near 3400-3600 cm-1 disappears as the intensities of the bands for the aldehyde C-H (2736 cm-1) and the aldehyde carbonyl (1695 cm-1) increase.

Reaction of PCTFE with a stoichiometric amount of chromium hexacarbonyl in DMF at 95°C for 5 days under a nitrogen atmosphere, followed by hydrolysis results in the formation of a brown-black polymer. Analysis of the infrared data indicates that carbonylation does indeed occur (Equation 11). The infrared absorption spectrum shows a large decrease in the C-Cl stretch at 970 cm-1 with a concomitant appearance of a very strong band in the carbonyl stretching region centered at 1680 cm1. There is also a broad band centered at 3490 cm-1 in the hydroxyl stretching region and two bands of moderate intensity... 

Fig. 7. Spectra of the hydroxyl stretching region of H Y, illustrating the interaction of OH groups with amines A, HY at 150° B, HY treated with excess pyridine at 35°, then degassed at 150°C C, HY treated with excess piperidine at 35" and degassed (41). (Reprinted with permission of the American Chemical Society.)...

Figure 10.1 FTIR-PA spectrum of the hydroxyl stretching bands of silica gel, (a) pretreated at 473 K, (b) reacted with BCl at 293 K. Spectrum (c) is the difference spectrum of (a) and (b).

Cation distributions in amphibole structures, the site occupancy data for which were obtained mainly from X-ray crystal structure refinements, Mossbauer spectroscopy and hydroxyl stretching frequency measurements in the infrared region, have been critically reviewed (Strens, 1974 Hawthorne, 198 la,b 1983). 

The exceptional strength of the hydrogen bonding is explained on the basis of the large contribution of the ionic resonance structure. Because of the strong bonding, a free hydroxyl stretching vibration (near 3520 cm-1) is observed only in very dilute solution in nonpolar solvents or in the vapor phase. 

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