A survey of the lone pair effect on the ring geometry of 1,2,4-triazoles and analogous 1,2,3-triazoles and imidazoles. The structures of 1-methyl-5-amino-3-methylthio-1,2,4-triazole, 1-phenyl-5-amino-3-methylthio-1,2,4-triazole and 1-(4-methylbenzyl)-3-amino-5-methylthio-1,2,4-triazole

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Abstract

The structures of the title compounds have been established by X-ray crystallography from diffractometer data. Crystals of the first (I), C4H8N4S, are monoclinic, space group P21/c, with a = 8.166(2), b = 10.481(1), c = 8.585(1) Å, β = 109.33(2)°, Z = 4, Dc = 1.381 g cm-3. Crystals of the second (II), C9H10N4S, are monoclinic, space group P21/c, with a = 11.850(4), b = 7.898(1), c = 23.981 (6) Å, β = 117.23(2)°, Z = 8, Dc = 1.373 g cm-3. Crystals of the third (III), C11H14N4S1 are also monoclinic, space group P21/c with a = 12.829(3), b = 8.348(1), c = 11.088(4) Å, β = 94.40(4)°, Z = 4, Dc = 1.314 g cm-3. The structures, determined by direct methods (I, III) and Patterson synthesis (II) were refined to R = 0.039 for 1070 reflections of I, R = 0.040 for 2792 reflections of II and R = 0.041 for 1900 reflections of III. The characteristic features of the planar five-membered rings are studied in comparison with the analogous 1,2,3-triazoles and imidazoles. It is shown that these planar rings exhibit only two patterns of the endocyclic bond angles induced dominantly by the number and relative position of the N-lone pairs. A similar effect of the double bonds (attached to C atoms) is also discussed.

Original languageEnglish
Pages (from-to)391-402
Number of pages12
JournalJournal of Molecular Structure
Volume102
Issue number3-4
DOIs
Publication statusPublished - Nov 1983

ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy
  • Organic Chemistry
  • Inorganic Chemistry

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