Hydrogen bonds infrared absorption

The exit gas from the generator ice trap is dissolved directly in water. The hydrogen-ion concentration of the resulting solution is determined by titration with standard base, and the iodide-ion concentration by the precipitation of silver iodide. Only traces of tetrahydronaphthalene are detected by the very slight carbon-hydrogen bond-infrared absorption in the samples of the anhydrous gas prepared by this procedure. 

Samples of a-Si H prepared under these conditions have an E°pt of 1.9-2.0eV and contain 10-15% of bonded hydrogen atoms. Infrared absorption measurement of a-Si H provides information about the Si-H bonding configuration (see Volume 2IB, Chap. 4 by Zanzucchi). 

The infrared spectra of A-4-thiazoline-2-ones are characterized by a strong absorption around 1650 cm (55, 86, 103, 107. 870). For the N-H derivatives, the whole range 2700 to 3200 cm is covered by a strong absorption related to the dimeric and oligomeric states of the hydrogen-bonded structures (85, 86). 

As discussed earlier in Section lOC.l, ultraviolet, visible and infrared absorption bands result from the absorption of electromagnetic radiation by specific valence electrons or bonds. The energy at which the absorption occurs, as well as the intensity of the absorption, is determined by the chemical environment of the absorbing moiety. Eor example, benzene has several ultraviolet absorption bands due to 7t —> 71 transitions. The position and intensity of two of these bands, 203.5 nm (8 = 7400) and 254 nm (8 = 204), are very sensitive to substitution. Eor benzoic acid, in which a carboxylic acid group replaces one of the aromatic hydrogens, the... 

Bohlmann et al. (118-121) observed that an infrared absorption band between 2700-2800 cm is characteristic of a piperidine derivative possessing at least two axial carbon-hydrogen bonds in antiperiplanar position to the free-electron pair on the nitrogen atom. The possibility of forming an enamine by dehydrogenation can be determined by this test. Compounds which do not fulfill this condition cannot usually be dehydrogenated (50, 122,123). Thus, for example, yohimbine can be dehydrogenated by mercuric acetate,whereas reserpine or pseudoyohimbine do not react (124). The quinolizidine (125) enamines (Scheme 4), l-azabicyclo(4,3,0)-nonane, l-azabicyclo(5,3,0)decane, l-azabicyclo(5,4,0)undecane, and l-azabicyclo(5,5,0)dodecane have been prepared in this manner (112,126). 

As mentioned in Section II,B, solutions of y9-hydroxypyridines in the nonpolar solvents chloroform and carbon tetrachloride show sharp infrared absorption bands near 3600 cm indicating that they exist in the hydroxy form. Infrared spectral data also led Mason to conclude that -hydroxypyridines probably exist largely as such in the solid state and exhibit O— 0 hydrogen bonding, a conclusion which is contrary to an earlier proposal favoring a zwitterion structure. 

During the reaction, protons are extracted from the brucite lattice. Infrared spectra [24, 25, 31] show that during charge the sharp hydroxyl band at 3644 cm" disappears. This absorption is replaced by a diffuse band at 3450 cm"1. The spectra indicate a hydrogen-bonded structure for ft-NiOOH with no free hydroxyl groups. ft-NiOOH probably has some adsorbed and absorbed water. However, TGA data... 

Infrared Hydroxyl Absorption Bands and Hydrogen-bonding Strength (Xv cm ) for Various Sugars and Their Relative Sweetness ... 

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