Determining the crystal structure of twinned 2-methylpyrazine.

Although systematic absences and symmetry relations among reflections pointed to space group I4(1)22 (one molecule in the asymmetric unit), a direct methods solution could only be obtained in I(-)4 (two molecules in the asymmetric unit). Refinement in I(-)4 was unsatisfactory until merohedral twinning was taken into account. The resulting molecular dimensions are in excellent agreement with analogous values in the literature. The molecular arrangement is described.