The structure of aminoazoles and its relationship with aromaticity. Crystal and molecular structure of two polymorphic forms of 4-aminopyrazole

Quantum mechanic calculations have been done at MP2 and B3LYP/ 6-31G** leve ls on six C-aminoazoles (alpha-aminopyrrole, 3-aminopyrazole, 5-aminopyrazo le, 4-aminopyrazole, 5-amino-1,2,4-triazole, and 5-amino-1,2,3,4-tetrazole) . These calculations have been used to discuss the molecular structure of t hese compounds in relation to their aromaticity. The crystal and molecular structure of two polymorphic forms of 4-aminopyrazole has been determined b y X-Ray analysis. The main differences, between the two polymorphs, at mole cular level lie in the conformation of the amino group and at the packing l evel in the hydrogen interactions involving the amino group.