Cyclotridecanone 2,4-dinitrophenylhydrazone.

In cyclotridecanone 2,4-dinitrophenylhydrazone, C(19)H(28)N(4)O(4), the 13-membered carbocycle exists in the triangular [337] conformation. The 2,4-dinitrophenylhydrazone group is almost perpendicular to the 13-membered ring, with a dihedral angle of 82.66 (2) degrees between the mean planes. The dinitrophenylhydrazone rings are packed parallel to each other and separated by 3.28 (1) A. The NH group forms an intramolecular hydrogen bond to a nitro O atom, and there is a weaker C-H...O interaction between a cyclotridecane CH group and a symmetry-related 4-nitro O atom, with a C...O distance of 3.436 (2) A and a 150 degrees angle about the H atom. The structure, in combination with additional evidence, indicates that [337] is the preferred conformation of cyclotridecane and other simple 13-membered rings.