Crystal and molecular structures of butan-2-one p-nitrophenylhydrazone (1), propanal 2,4-dinitrophenylhydrazone (2), dimethyl 2-oxo-propanedioate phenylhydrazone (3), and dimethyl 2-oxopropanedioate 2,4-dinitrophenylhydrazone (4): hydrogen bonding and bond order in phenylhydrazones

Abstract

Crystals of the title compound (1), C₁₀H₁₃N₃O₂, are monoclinic, a= 4.119(11), b= 18.992(12), c= 13.992(10)Å, β= 96.0(1)°, space group P2₁/c, Z= 4. Compound (2), C₉H₁₀N₄O₄, is monoclinic a= 5.333(7), b= 11.488(8), c= 17.713(10)Å, β= 95.0(1)°, space group P2₁/c, Z= 4. Compound (3), C₁₁H₁₂N₂O₄, is monoclinic, a= 21.331(14), b= 4.153(10), c= 13.640(12)Å, β= 102.8(1)°, space group P2₁/a, Z= 4. Compound (4), C₁₁H₁₀N₄O₈, is monoclinic, a= 11.198(8), b= 14.779(9), c= 8.443(7)Å, β= 92.4(1)°, space group P2₁/a, Z= 4. All four structures were solved by the statistical method using the SHEL-X-76 system of programs, and refined using full matrix least squares. The numbers of reflexions used in refinement and the final R values are (1) 330, 0.103; (2) 611, 0.059; (3) 863, 0.061; and (4) 1 274, 0.070, respectively. In all cases the (NO₂)–Ar–NH–NC–(CO) fragment is essentially planar. The NO₂⋯ HN and CO ⋯ HN separations suggest that there is substantial intramolecular hydrogen bonding. In addition in compound (2) there is evidence for intermolecular as well as intramolecular NO₂⋯ H–N bonding in the crystal. In phenylhydrazones whose structures are known, there is an inverse relationship between Ar–NH and N–N bond lengths, and a direct relationship between Ar–N(H) and NC bond lengths.