The structure of N-(azol-N-yl) formamides: a crystallographic and dynamic NMR spectroscopy study

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Abstract
The molecular structures of N-(pyrazol-1-yl) formamide 1[C4H5N3O, orthorhombic, space group P212121, a= 5.269(8). b= 8.039(8). c= 12.79(2), Z= 4] and N-(indazol-1 -yl) formamide, 5[C8H7N3O, monoclinic, space group P21/c, a= 9.065(2). b= 11.089(7), c= 8.463(7), Z= 4] have been solved by X-ray crystallography. Regarding the amide bond, both compounds exist in the Z configuration, a configuration which also prevails in solution for all the N-H azolyl formamides whilst the N-substituted derivatives prefer the E configuration. The rotation barriers about the amide bond are similar although a little lower than those of N-phenylformamide and N-methyl-N-phenylformamide, a fact that may be related to the electronic properties of the N-azolyl substituent.