Four trifluoromethylnitrobenzene analogues.

The crystal structures of four trifluoromethylnitrobenzene analogues (CF(3))C(6)H(3)(NO(2))[C(4)H(8)N(2)]R (where C(4)H(8)N(2) is piperazinyl and R is ethyl carboxylate, CO(2)C(2)H(5), or phenyl, C(6)H(5)), have been determined, and their conformations and packing arrangements are compared. The four compounds are ethyl 4-[4-nitro-2-(trifluoromethyl)phenyl]piperazine-1-carboxylate, (I), and ethyl 4-[2-nitro-4-(trifluoromethyl)phenyl]piperazine-1-carboxylate, (II), both C(14)H(16)F(3)N(3)O(4), and 1-[4-nitro-2-(trifluoromethyl)phenyl]-4-phenylpiperazine, (III), and 1-[2-nitro-4-(trifluoromethyl)phenyl]-4-phenylpiperazine, (IV), both C(17)H(16)F(3)N(3)O(2). All molecules adopt a rod-like conformation, while the asymmetric units of (II) and (IV) contain two unique molecules that pack as monodirectional pairs. All molecules pack with C-H...O/F close contacts to all but one of the O atoms and to five of the 18 F atoms.