Infrared spectroscopy structural hydroxyl groups

Russell, J.D. (1979) Infrared spectroscopy of fer-rihydrite evidence for the presence of structural hydroxyl groups. Clay Min. 14 109—114 Russell, J.D. Parfitt, R.L., Eraser, A.R. Farmer,... 

These structural problems are also insoluble by physical methods alone. The infrared spectrum often gives an unambiguous decision about the structure in the solid state the characteristic bands of the carbonyl or the hydroxyl group decided whether the compound in question is a carbinolamine or an amino-aldehyde. However, tautomeric equilibria occur only in solution or in the liquid or gaseous states. Neither infrared nor ultraviolet spectroscopy are sufficiently sensitive to investigate equilibria in which the concentration of one of the isomers is very small but is still not negligible with respect to the chemical reaction. 

Preliminary examinations of dextran structures were conducted by optical rotation, infrared spectroscopy and periodate-oxidation reactions. More detailed results can be achieved by methylation analysis [19]. The hydroxyl groups are methylated with methyl iodide after activation with sodium methylsulfinyl carbanion (Fig. 2). The methyl dextran is hydrolysed to the corresponding different methylated monosaccharides, which are furthermore reduced and peracetylated. The resulting alditol acetates of methylated sugars are separated by gas chromatography and identified by their retention times. In particular, a combined capillary gas-liquid chromatography/mass... 

Oare earth forms of zeolites X and Y type faujasites possess superior catalytic properties for various reactions such as alkylation, isomerization, and cracking (9, 12, 18). Structural studies involving x-ray diffraction and CO chemisorption have been made to locate the positions of the rare earth (11, 14, 16). Hydroxyl groups and their relationship to surface acidity have been studied by infrared spectroscopy, utilizing the adsorption of pyridine and other basic molecules (2, 6, 21, 22, 23). Since much of the previous research has involved measurements on mixed rare earth faujasites, a need existed for a more systematic study of the individual rare earth zeolites, in regard to both structural and catalytic properties. The present investigation deals with the Y, La, Ce, Pr, Sm,... 

The infrared spectroscopy shows the presence of surface SiOH groups [35,36]. Infrared spectra also reveal the surface B-OH groups but only after degasing of CPG at elevated temperatures under vacuum conditions [32-34,37], Geminal OH structures bonded with Si as well as B atoms can be detect among hydroxyl groups [38]. 

Let ns stay a bit with the example of the spectroscopist. Let ns assume he is a specialist in infrared spectroscopy. One of the features of a structural drawing he wonld pay special attention to is hydroxy groups. The reason he does this is because his experience tells him that hydroxyl groups can usually be seen as a broad band at the beginning of an infrared spectrum. He translates this information almost automatically into a hydroxyl band in the spectrum. 

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