But-2-enal 2,4-dinitro-phenyl-hydrazone.

In the title compound, C(10)H(10)N(4)O(4), the but-2-enal chain is almost planar, the largest deviation from the mean plane being 0.013 (1) Å, and this plane makes a dihedral angle of 9.95 (24)° with the benzene ring,. Of the two nitro groups, one is twisted with respect to the benzene ring, making a dihedral angle of 5.7 (1)°, whereas the other is nearly in the plane of the benzene ring, with a twist angle of only 0.7 (1)°. This difference is related to the occurence of an intra-molecular N-H⋯O hydrogen bond with the O atom of the less twisted nitro group. The NH group is also involved in a weak inter-action with the same O atom of a symmetry-related mol-ecule, thus forming a pseudo inversion dimer.