Synthesis and Crystal Structure of 4,4-(Methylenediimino)bis-1,2,5-Oxadiazole-3-carboxylic Acid and Carboxamide
Polymers and High Performance Materials
4,4-(Methylenediimino)bis-1,2,5-oxadiazole-3-carboxylic acid and 4,4-(methylenediimino)bis-1,2,5-oxadiazole-3-carboxamide have been synthesized by the acid-catalyzed condensation of 4-amino-1,2,5-oxadiazole-3-carboxylic acid and 4-amino-1,2,5-oxadiazole-3-carboxamide with formaldehyde. The crystal and molecular structures of the compounds have been determined by X-ray crystallography. 4,4-(Methylenediimino)bis-1,2,5-oxadiazole-3-carboxylic acid crystallizes in space group C2/c, and its measured density is 1.800g/mL, significantly above the calculated value of 1.68g/mL. 4,4-(Methylenediimino)bis-1,2,5-oxadiazole-3-carboxamide crystallizes in space group P21/c, and its measured density is 1.623g/mL, in close agreement with the calculated value of 1.64g/mL. The structure of the starting amide 4-amino-1,2,5-oxadiazole-3-carboxamide has also been determined. These data, combined with literature data, suggest that ortho-aminocarboxylic acids have unusually high densities, but the reasons for this are unclear.
Journal of Heterocyclic Chemistry
(2013). Synthesis and Crystal Structure of 4,4-(Methylenediimino)bis-1,2,5-Oxadiazole-3-carboxylic Acid and Carboxamide. Journal of Heterocyclic Chemistry, 50(4), 949-954.
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