Hydroxyl stretch frequency

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). 

Pak has shown, by a correlation between O—H stretching frequency and the strength of the M—OH bond, that the Bronsted acidity of ZnO is similar to that of MgO and NiO and is much less than that of y-Al20a. A similar conclusion was reached from studies of benzene adsorption and of its effect on hydroxyl stretching frequencies, a for ZnO of 10.5 being reported. In general then we may expect ZnO to display basic/Lewis acid properties in catalytic reactions, as shown by MgO, on which carbanions are readily produced from both alkenes... 

Other instances of a low hydroxyl-stretching frequency arising from the hydroxyl group (s) on a pair of 1,3-m-diaxial C—0 bonds have been reported in the spectra of methyl 2-C-methyl- 3-L-ribopyranoside (at 3512 cm. ) and methyl 3,6-anhydro-a-D-glucopyranoside (at 3500 cm. 0-The latter compound is constrained in the 1C conformation, and the band at 3512 cm. shows that the former compound is in the 1C conformation also. The occurrence of this characteristically low frequency in the spectra of some branched-chain sugars enabled their configuration to be determined by indicating the presence of such diaxial C—0 bonds. ... 

It has been shown that the majority of the polar moitles in epoxy-diamine networks, such as hydroxyl groups generated by the cross-linking reaction and residual amino hydrogens, take part in inter- or intramolecular hydrogen bonds (6, 7 ). Indeed, at ambient temperatures, the infrared hydroxyl stretch frequency of epoxy-diamine systems are characteristically shifted from its free value of 3600 cm-1 to a hydrogen bonded value of 3440 cm 1 (8). 

Libowitzky [21] showed that a regression function can be employed relating the hydroxyl stretching frequencies to the O - O distance, with regression coefficients better than 0.96 using infrared spectroscopy. The flmction is described as ... 

Fig. 9. IR spectra of the hydroxyl stretching frequency region after degassing at 723 K for 2 h (final vacuum about 10 Pa), a H-ZSM-5 b NaCl/H-ZSM-5 mixture (%aci/nAi = 1-89) calcined at 900 K for 1 h c (b) washed with water d (b) twice exchanged with 1N NH4CI solution (after...

Fig. 10. IR spectra of the hydroxyl stretching frequency region after degassing of a NH4-Y at 725 K for 12 h (final vacuum about 10 Pa) and b CSCI/NH4-Y (ncs/nAi = 1.1) at 725 K for 20 h (ex situ SSIE) and subsequently for 2 h in high vacuum (in situ SSIE) degree of exchange in NH4-Y was 98%...

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