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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...
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...
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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