Two solid phases of pyrimidin-1-ium hydrogen chloranilate monohydrate determined at 225 and 120 K

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Abstract

The crystal structures of two solid phases of the title compound, C4H5N2 +·C6HCl2O4 -·H2O, have been determined at 225 and 120 K. In the high-temperature phase, stable above 198 K, the transition temperature of which has been determined by 35Cl nuclear quadrupole resonance and differential thermal analysis measurements, the three components are held together by O-H⋯O, N⋯H⋯O, C-H⋯O and C-H⋯Cl hydrogen bonds, forming a centrosymmetric 2+2+2 aggregate. In the N⋯H⋯O hydrogen bond formed between the pyrimidin-1-ium cation and the water molecule, the H atom is disordered over two positions, resulting in two states, viz. pyrimidin-1-ium-water and pyrimidine-oxonium. In the low-temperature phase, the title compound crystallizes in the same monoclinic space group and has a similar mol-ecular packing, but the 2+2+2 aggregate loses the centrosymmetry, resulting in a doubling of the unit cell and two crystallographically independent molecules for each component in the asymmetric unit. The H atom in one N⋯H⋯O hydrogen bond between the pyrimidin-1-ium cation and the water molecule is disordered, while the H atom in the other hydrogen bond is found to be ordered at the N-atom site with a long N-H distance [1.10 (3) Å].

Original languageEnglish
Pages (from-to)o114-o118
JournalActa Crystallographica Section C: Crystal Structure Communications
Volume66
Issue number3
DOIs
Publication statusPublished - Mar 16 2010

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ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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