PubMed · 13067553
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BROUET. 1953-04-18. [Isoniazid].. https://pubmed.ncbi.nlm.nih.gov/13067553/
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The conventional (non-polarized) and linear-polarized IR-spectra of 2-pyrrolidone and laurolactam as typical representatives of lactams with cis- and trans-amide configuration, respectively, were studied by means of difference IR-spectroscopy. The application of this method to treatment of the non-polarized IR-spectra permits additional conclusions about the likely self-associates of these compounds dissolved in aprotic solvents. By means of the difference linear-dichroic IR-spectroscopy, a more precise assignment of the characteristic bands of the lactam cis- and trans-peptide forms as well as their stereo structures were accomplished. A comparative analysis with the linear-dichroic IR-spectra of epsilon-caprolactam and caprylolactam, as similar compounds, with cis- and trans-conformation, respectively, was also carried out.
From pure powders of forms I and II of phenobarbital, X-ray diffraction patterns were recorded at room temperature. The starting crystal structural models were found by a Monte-Carlo simulated annealing method. The structures of the two forms were obtained through Rietveld refinements. Soft restraints were applied on bond lengths and bond angles, all H-atom positions were calculated. The cell of form I is monoclinic with the space group P2(1)/n, Z=12, Z'=3. Form II has a triclinic cell, with the space group P1 , Z=6, Z'=3. For both forms, the crystal cohesion is achieved by networks of N-H...O hydrogen bonds along [101]. The broadening of the Bragg peak profiles is interpreted in terms of isotropic strain effects and anisotropic size effects.
Chemical preparation, infrared and Raman spectra of sodium samarium fluorosilicate, NaSmSiO(4).0.25NaF are presented. The spectra are analyzed with regard to the symmetry, and the numbers of the SiO(4)(4-) internal vibrational modes observed in the Raman and infrared spectra are consistent with the predictions.