| Abstract: | The structures of 1‐methyl‐3‐nitropyrazole and 1‐methyl‐4‐nitropyrazole, C4H5N3O2, have been determined. The 3‐nitro derivative has crystallographic m‐symmetry while the 4‐nitro compound has no imposed symmetry. The significant differences in bond distances and angles between the structures are ascribable to the electron‐withdrawing effects of the nitro group attached to C3 or C4, respectively. In both structures, the molecules are organized into layers by an extensive network of C—H?O or C—H?N hydrogen interactions. Within a layer, the molecules are arranged in a similar way, although differences of up to 0.3 Å in the analogous H?O or H?N intermolecular distances are observed. The cohesion of the layers is due to van der Waals and C—H?O contacts. |
