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A review of our latest vibrational researches performed at the “Centro Studi di Spettroscopia Raman” of Bologna University on systems characterized by “strong” hydrogen bonds is given and discussed. This research arises from our previous studies on the problem of “anomalous” water and deals with solid and liquid , concentrated aqueous solutions of strong inorganic acids and bases, concentrated anhydrous solutions of HCl in MeOH, and with a structural model of the concentrated aqueous solutions...
To persue our foregoing researches, the problem of anomalous water is considered relative either to necessary conditions for the strong O--H--O hydrogen bonds forming or to liquid phenomena in capillaries. Anomalous water does not exist as allotropic modification of water, and its properties cannot be attributed to impurities, simply. With a good probability, the problem of anomalous water invests a more vast problem concerning the anomalies of physic properties of liquids in capillaries and superficial...
Glasses of composition xAsO-NaO and xAsO-KO have been prepared and Raman and i.r. spectra studied in relation to the vitreous AsO spectra, previously examined. In glasses richer in AsO, structural centers of vitreous AsO-namely of the claudetitic type-are present together with centers, typical of alkaline metaarsenite structure, which increase as the alkaline oxide percentage increases. Differently from vitreous AsO, which, in time, modifies its structure passing from a claudetitic type to an arsenolitic...
A series of vibrational Raman and i.r. spectroscopic researches on inorganic glasses based on BO(BO, BO-xHO, xBO-NaO), AsO(AsO, xAsO-NaO, xAsO-KO) and PO(NaO-PO, xNaO-PO) is here resumed and discussed. Vitreous BO has a structure containing BO(O) rings, where the boron atoms are trigonally coordinated with oxygen. The structure of AsO glass is mostly of the claudetitic type (formed by double indefinite chains) while the Graham salt (NaO-PO) structure is of the linear polymeric type. An addition...
U.r. and Raman spectra of glasses of composition (x = 2, 3, 4, 5, 6 e 9) are reported. By comparison with known crystalline structure of borate and polyborate u.r. spectra, it is possible to reveal a gradual boron transformation from trigonal to tetrahedral coordination, when the NaO percentage in glass composition rises. The Raman spectra too support this behaviour, moreover we may characterize the presence of BO(O) rings in the glass structure by a typical band near 800 cm. Heating the materials...
Vibrational spectra of binary glassy materials (Ramanand u.r.), (u.r.) and (u.r.) are reported and discussed. In the case of systems, spectra interpretation suggests a modification of and structures and the formation of structural centers typical, respectively, of metaarsenites and metavanadates. For these demolitions, the probable mechanisms are proposed. In the case of system (64-30% of ), the spectra agree with the ortho-, pyro-, metavanadates formation hypothesis together with...
Raman spectra of materials of binary molar composition BO/LiO variable between 9 and 1 in the glassy system BO-LiO are discussed relatively to the "boric anomaly" phenomenon presented by these glasses and relatively to the measures of diamagnetic anisotropy and nuclear magnetic resonance made by other Authors. In analogy to these latest measures the presence of structural centers consisting of boroxol groups BO(O) is made evident in the glasses richest in BO up to the composition 3BO-LiO. Moreover...
Infrared spectra of the materials composing the system have been examined. films laid down from a n-hexane suspension on KBr disks were heated to controlled temperatures in the atmosphere, under vacuum (mmHg) and at the vapour pressure of 21 mmHg. Infrared spectra indicate that a direct transformation of into anhydrous occurs in a definite temperature interval, which depends on each case. Infrared spectra, recorded from film heated under the vapour pressure of 140 mmHg, show, on the contrary,...
Infrared spectra of aqueous solutions of dimethylsulphoxide (DMSO) in a wide range of concentrations are presented and discussed. The present work is preliminary to a wider research including Raman laser and near infrared vibrational investigations. In the infrared spectra it is possible to observe the presence of at least three components in a certain range of more concentrated solutions, and the presence of a single component in the case of more dilute solutions. As a preliminary hypothesis,...
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...
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...
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....
U.r. spectra of NaHPO - 2HO samples at room temperature and after heating at 175,235 and 370 °C, are reported. At these temperatures thermogravimetric analysis indicates the loss of 2, 1/2 and 1/2 water molecules, respectively. U.r. spectra agree with NaHPO formula for the salt heated at 175 °C, with NaHPO for that heated at 235 °C and with NaPO for that heated at 370 °C. Bands corresponding to typical vibrations are discussed for each species. Particularly, in the case of NaPO, u.r. spectra makes...
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....
A structural model for the concentrated aqueous solutions of electrolytes is assigned by spectroscopical-vibrational data. The model is then applied to the concentrated aqueous solutions of guanidinium hydro chloride, considering Raman, i.r. and near i.r. spectra. Guanidinium hydrochloride has been chosen because it shows denaturing properties in regard to proteins in concentrated aqueous solutions. The aim of this work is to give a first contribution to the study of the denaturing mechanism, considering...
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...
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