G. Argay, A. Kălmăn, J. Kovács
Oct 15, 1990
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Journal
Journal of Molecular Structure
Abstract
Abstract The structure of 4-amino-( Z )-5-(4′-hydroxy-( E )-but-2′-enlydinene)-1,5-dihydro-2 H -imidazol-2-one monohydrate has been established by X-ray crystallography from diffractometer data: C 7 H 9 N 3 O 2 ·H 2 O ( M r -185.18) crystallizes in the orthorhombic, space group P 2 1 2 1 2 1 with a -4.591 (1) A, b =9.952 (3) A, c -19.271 (3) A, V -880.6 (6) A 3 , Z -4, D c -1.40 g cm −3 and μ(Cu K α)=9.0 cm −1 . The structure has been solved by direct methods and refined to R =0.037 for 777 observed reflections. While substantiating the molecular geometry inferred from NMR spectra, the X-ray analysis revealed that, in contrast to the preponderance of the 4-imino tautomer ( IIb ) in solution, in the crystalline state only the 4-amino form ( IIa ) is present. In solution, the 4-amino tautomer is terminated by the short intramolecular =CH⋯H(NH)− close contact of 2.14 A repulsing hte contact amino proton to N(3), whereas in crystalline state the hydrogen-bond network developed between the molecules with the assitance of the solvent (water) molecule seems to account for its stability. Among others, the N(1)−H⋯N(3) intermolecular hydrogen bond hardly tolerates a simultaneously protonated N(3) atom required by tautomer IIb .