Determining the crystal structure of twinned 2-methylpyrazine

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