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In previous vibrational researches, we have studied the behaviour of the peptide group in various environments. Now, infrared and Raman spectra of crystalline diketopiperazine and Raman spectra of its saturated aqueous and aqueous acid (in 6 and 12 N HCl) solutions are reported and discussed. Raman spectra of this cyclic dipeptide are not reported in the literature. A substantial modification is observed in the Raman spectra going from crystalline form to solution, and it is attributed to intermolecular...
Raman (1450-4500 cm) and near i.r. spectra (4000-7500 cm) of HCl and NaOH aqueous solutions are discussed. Concentrated solutions contain H(HO) and OH-(HO) ions; they are characterized by a first "coordination-sphere" with strong (O--H--O) and (O--H--O) hydrogen-bond between H, or OH, ions and water molecules and by successive "coordination-sphere" with OHO hydrogen bonds of decreasing strength. Concentrated solutions display a large Raman continuous band that extends from the region of stretching...
Raman Laser and I.R. spectra of vitreous (NaPO) (Graham's salt), crystalline ((NaPO) (Maddrell's salt), crystalline sodium trimetaphosphate NaPO and vitreous sodium olygophosphates with molar ratios NaO/PO between 1 and 1.625 are here reported. By comparison of Graham's salt spectra with those of Maddrell's salt and trimetaphosphate, it is possible to confirm, for Graham's salt, the polyphosphatic linear chain structure. Evidence is shown for the analogy between the I.R. and Raman spectra of vitreous...
I.r. and Raman spectra of acetamide CHCONH and its emicloridrate (CHCONH)·HCl are reported and discussed. I.r. spectra of (CHCONH)·HCl shows a large and strong absorption about 850 cm, which is absent in the i.r. spectrum of CHCONH and in the Raman spectra of CHCONH and (CHCONH)·HCl. Such a band can be attributed to an antisymmetric stretching vibration of (O--H--O) strong symmetric hydrogen bond between the carbonyl groups of the (CHCONH)·H ion, vibration which is allowed in i.r. but not in Raman....
Infrared and Raman spectra of aspirin and KH diaspirinate are reported and discussed in relation to the strong hydrogen bonds shown by these compounds, according to X-ray and neutronic diffraction data of the literature. This discussion is at the basis of a hypothesis put forth here on the probable inhibition mechanism of prostaglandin biosynthesis by aspirin-like drugs. The hypothesis considers the formation of strong hydrogen bonds between the acid function aspirin-like drugs and the basic enzime...
Raman spectra of acetamide CHCONH in aqueous solution and in aqueous acid (HCl) solutions are given and discussed. The spectra make evident a gradual transformation of acetamide from a free to a protonated form. A structural hypothesis—oxonium ion—for the protonated form in aqueous acid solutions is advanced, extending the discussion to the Raman spectra of acetamide in aqueous (DO) acid (DCl) solution, of acetamide hydrochloride (CHCONH)-HCl, crystalline and in aqueous acid solution, of acetic...
A thin film of arsenic trioxide was compressed between two alkali halide discs and heated up to 15o°C for 12 hours. Several modifications, which are stronger going from KCl to KBr to KI and depend on the activation of alkali halide and on water vapour absorbed, are observed in the i.r. spectra of the thin film. They are attributed to surface interaction between the film and the alkali halide discs and emphasize the change of the film structure from "arsenolite" towards a "claudetite" type structure...
The structure of AsO glass has been studied by Raman and i.r. spectroscopy in relation to the structures of the two polymorphic crystalline modifications of AsO, arsenolite and claudetite. The claudetite has been prepared in laboratory and for the first time its Raman and i.r. spectra (extended to 200 cm) are given. Contrary to the conclusions of foregoing Authors who ascribe to AsO glass an arsenolite structure, the Raman and i.r. spectra of AsO obtained by us accord better with a claudetite structure....
Raman and i.r. spectra of vitreous sodium oligophosphates , with x between 1,000 and 1,625 are reported and discussed. As x increases, gradual modifications are particularly observed in the Raman spectra by the weakening of some typical bands of the glass with x = 1,000—Graham salt-—and the appearance of new bands. In the spectra of the glass with x = 1,625 these bands are discussed in relation to the Raman spectra of melted polyphosphates with low molecular weight.
This work concerns the spectroscopic vibrational study of the different polymorphic forms of cholesterol (anhydrous, monohydrate and form II) known in the literature in order to complete a program of vibrational researches on the structure and composition of gallstones. These three forms of cholesterol are distinguishable in i.r. spectra for the region of stretching. In particular, the structure of the water in monohydrate cholesterol has been examined relatively to a recent x-ray study. The structure...
I.r. spectra of a series of cholesterol gallstones are given and discussed in order to identify the different forms of cholesterol, anhydrous, monohydrate, form II (these forms have recently been characterized spectroscopically by us) and to reveal the other components associated with them in gallstones. It was also revealed spectroscopically that the main component in the gallstones examined was cholesterol monohydrate generally in association with organic (bilirubinate, palmitate) calcium salts....
Raman an di.r. spectra of anhydrous hydrogen chloride solutions in methanol are preliminarly anticipated in a program of vibrational studies on strong hydrogen bond. The spectra evidence the formation of protonated species corresponding to that , that we have observed in the Raman spectra of aqueous hydrogen chloride solutions, and they show an analogous behaviour. We shall give more detailed references in a next work.
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