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The structure of cimetidine (C 10 H 16 N 6 S) solved from synchrotron‐radiation X‐ray powder diffraction data
Author(s) -
Cernik R. J.,
Cheetham A. K.,
Prout C. K.,
Watkin D. J.,
Wilkinson A. P.,
Willis B. T. M.
Publication year - 1991
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889890013486
Subject(s) - monoclinic crystal system , synchrotron radiation , crystal structure , crystallography , synchrotron , atom (system on chip) , powder diffraction , fourier transform , diffraction , materials science , x ray crystallography , x ray , resolution (logic) , analytical chemistry (journal) , physics , chemistry , optics , chromatography , quantum mechanics , artificial intelligence , computer science , embedded system
The crystal structure of cimetidine (C 10 H 16 N 6 S) has been solved and refined from high‐resolution synchrotron X‐ray powder data collected on station 8.3 at Daresbury Laboratory. The structure is monoclinic, P 2 1 / n , Z = 4, a = 10.7029 (3), b = 18.8262 (1), c = 6.8266 (2) Å, β = 111.306 (2)°. The data were auto‐indexed and the integrated intensities were obtained by pattern decomposition. The structure was solved by direct methods followed by iterative cycles of least‐squares refinement and Fourier syntheses. All 17 non‐H atoms were located. The structure was then refined using the method of Rietveld [ J. Appl. Cryst. (1969), 2 , 65–71]. A difference Fourier synthesis after the convergence of the non‐H‐atom model showed positive electron density at the expected positions of all 16 H atoms, ten of which were significantly above the background. The H atoms were allowed to refine unconstrained and the final agreement factors were R I = 1.9, R wp = 8.5 and R ex = 6.9%; the equivalent R ‐factors without the H atoms were R I = 10.3 and R wp = 16.2%, demonstrating the significant contribution of the H atoms to the profile.