A critical evaluation of the published information accompanied by additional studies allowed the elucidation of 3-amino-1,2,4-triazole reactivity in Biginelli-like condensations.

An X-ray diffraction study revealed the existence of 3,4-diamino-1,2,4-triazole in the crystal phase in two polymorphic modifications differing in the relative orientation of the molecules with respect to each other. A comparison of the character of the intermolecular interactions in the crystals of the polymorphic modifications suggests that polymorphism may be due to the formation of different weak hydrogen bonds while stronger H bonds and stacking interactions are similar in the two crystal structures. Calculations of the intermolecular interaction energy by the MP2/aug-cc-pvdz method allows determination in both crystal layers containing the strongly bonded molecules differing in the two polymorphic modifications. This approach distinguishes unambiguously the main structural pattern of packing of the molecules in the crystals of both polymorphic modifications.