Crystal structures of 1,1'-di(2-propanone)-2,2'-biimidazole dihydrazone and 2,6-diacetylpyridine dihydrazone

The nucleophilic addition reactions between 1,1'-di(2-propanone)-2,2'-biimidazole or 2,6-diacetylpyridine and hydrazine hydrate afford I,1'-di(2-propanone)-2,2'-biimidazole dihydrazone (1) and 2,6-diacetylpyridine dihydrazone (2), respectively. Compound 1 crystallizes in the orthorhombic space group P2(1)2(1)2(1), with a = 9.042(2), b = 9.731(3), c = 15.683(4)Angstrom, V = 1379.9(6)Angstrom(3) and Z = 4. Compound 2 crystallizes in the orthorhombic space group Pnma, with a = 10.948(2), b = 19.742(6), c = 4.566(1)Angstrom, V = 986.9(4)Angstrom(3) and Z = 8. A pseudo center of inversion is present at the midpoint of the C-C bond joining the imidazole rings of 1, whose substituents crystallize in a trans configuration. The imidazole rings are rotated 2.5(3)degrees about the C-C bond. In contrast to the essentially planar structure of 2, the hydrazone substituent groups of 1 are at angles of 89.9(1)degrees and 88.4(1)degrees with respect to the plane of the adjacent imidazole moiety.