Infrared spectra hydrates

Dehydration of gibbsite under pressure in moist air produces boehmite (aluminum oxide mono-hydrate). An infrared spectrum of boehmite (Kaiser substrate grade alumina) is shown in Figure 3c. 

Both the dimer and the photohydrate from photolysis of uracil have been isolated not only as spots on a chromatogram7 but also as crystalline or amorphous solids—the dimer by Smietanowska and Shugar45 and Swenson and Setlow48 and the hydrate by Gattner and Fahr.45 Many physical properties have not been recorded for these materials. The melting points of the principal dimer is 380°.34 The infrared spectrum is not reported. The elementary composition of the hydrate has been reported.45 ... 

The relationship of Lewis and Brpnsted acid site concentrations on H—Y zeolite was explored further in a study by Ward (156) of the effect of added water. At low calcination temperatures (<500°C) only a small increase in the Brpnsted acid site concentration occurred upon addition of water to the sample. Rehydration of samples dehydroxylated by calcination above 600°C resulted in a threefold increase in the amount of Brpnsted-bound pyridine. However, no discreet hydroxyl bands were present in the infrared spectrum after rehydration. Thus, the hydroxyl groups reformed upon hydration must be in locations different from those present in the original H—Y zeolite, which gave rise to discreet OH bands at 3650 and 3550 cm-1. 

The infrared spectrum of a protein is dominated by its peptide backbone amide I (C=0) and amide II (C-N. NH) vibrations. Fig. 6.6-1 shows a typical IR absorption spectrum of a hydrated protein film, in this case bacteriorhodopsin. In addition to the strong amide I (1658 cm ) and amide II (1546 cm ) bands water also contributes largely to the absorption (3379 cm , 1650 cm ). 

Commercial grade (NH4)2[OsCl6] (2.37 g) is added in small portions to ice-cold hydrazine hydrate (85 %, 23 ml). After the vigorous effervescence subsides, the solution is refluxed, with stirring, for 15 hr. A yellow precipitate of [Os(NH3)5(N2)]Cl2 is formed and is filtered from the cooled mixture, washed with ethanol and ether, and air-dried. To the filtrate is added solid potassium iodide until precipitation of [Os(NH3)5(N2)]l2 is complete. The product is collected on a filter and washed and dried as above. The chloride salt is converted to the iodide by metathesis using solid potassium iodide until precipitation is complete. Total yield of [Os(NH3)s(N2)]l2 2.36 g (78%). Anal. Calcd. for OSN7H15I2 N, 17.6. Found N, 17.0. Infrared spectrum, v(N2)(iodide salt) = 2033 (vs) 2043 (sh). 

The hydrated product (which may also be designated as UO3 2H2O or H2UO4 H2O) was identified by its powder pattern and its infrared spectrum. 

Tbe effect of hydration on the infrared spectrum of a 7.6 mole % H-SPS is shown in figure 3. After 19 hours the sample absorbed about 9% water, which corresponds to 9 moles H O per sulfonic acid group. This was accompanied by a ljirge decrease in the intensity of the absorbance band at 1176 cm and increases in the intensities of the bands at 1126 cm and 1007 cm. This result was expected, since upon hydration the acidic proton of the sulfonic acid is removed from the anion (1176 cm is characteristic of the S 0 symmetric stretch of the -SO.H and 1126 cm and 1007 cm are due to the ln-plane skeleton and the in-plane bending vibrations of a benzene ring with a SO, group attached). An absorbance at 1033 cm in the 19 hour sample is due to the symmetric stretch of the -SO and is further evidence of hydration Similarly, the decrease in intensity of the band at 1100 cm in the hydrated sample indicates that fewer -SO.H groups are present. 

Most of the studies described above were on partially hydrated protein powders or films. It is necessary to relate the conformation of the protein in this state to that in solution. There is a substantial body of evidence supporting the conclusion that the conformation of the protein does not change measurably between about 0.2 ti and the dilute solution 1) enzymatic activity is observable at 0.2 li. 2) The infrared spectrum changes continuously with hydration above 0.1 li and is consistent with surface group hydration without change in protein conformation. 

Sites Sp-Gp achieve a somewhat concave step, accommodating what has been called inner silanols (22). The present assignment gives an improved picture of the surface and of the hydration mechanism of a fumed silica. However, the infrared spectrum is intricate, and its assignment is still partly speculative. Whereas the comparison of the infrared and Raman spectra supports the conclusion that the formation of three-fold rings is mainly due to the condensation of weakly perturbed silanols (that absorb above about 3600 cm-1), the reciprocity is not warranted. For instance, the contribution of isolated silanols (i/OH = 3750 cm-1), postulated by Brinker et al (16), is excluded. In fact, a further analysis of both spectra will be necessary to know their relation to the various sites of a silica. 

A complex (NH4)[Zr(02)I 5] H20 was crystallized from a solution made by dissolving freshly prepared hydrated zirconium hydroxide in cold (—5°C) 40% hydrofluoric acid, then adding excess 30% hydrogen peroxide, and finally aqueous ammonia until pH 7 is reached. The infrared spectrum showed vq q at 839w, at 555w, and at 480s, br (226). 

Dimethyl sulfoxide adducts of zirconium perchlorate were prepared (326) by dissolving the metal perchlorate hydrate in dimethyl sulfoxide at 20°C. The addition of a large excess of benzene resulted in the precipitation of white, crystalline, Zr0(C104)2 8DMS0. The infrared spectrum shows an adsorption at 1024 cm due to the presence of unbound S=0,... 

An understanding of the infrared spectrum of chloral hydrate should be approached from a study of the spectrum of chloral, which has been described in some detail in the literature 1 2,3. Chloral hydrate has been shown to have a gem-diol structure by Raman spectra and by N.M.R.5 Comparison of the infrared (mull) spectra of the compound and of its deuterated analogl71 indicates that the two OH groups are not equal. This is confirmed by solution spectra sl8,23,168,171 and Ogawa23 suggests that chloral hydrate exists in solution in an equilibrium state, which may be represented as follows -... 

SchillS rejected the possibility of enantiotropy or the existence of isomeric forms of chloral hydrate. However, he was able to prepare a hemihydrate (m.p. 95°C) reproducing the work of Meyer and Dulkl24, Piguet and Jacot-Guillarmod7 more recently prepared a "hemihydrate" that gave a well-defined infrared spectrum different from those of chloral hydrate or of a mixture of chloral and chloral hydrate. 

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