Two polymorphic forms of the oxathiin systemic fungicide active carboxine

Two polymorphic crystal forms of the title compound, C(12)H(13)NO(2)S (systematic name: 6-methyl-N-phenyl-2,3-di­hydro-1,4-oxathiine-5-carboxamide), were isolated from a truncated, (12 solvent), polymorph screen on pure lyophillized material. Crystals of form 1 were obtained from all solvents included in the screen with the exception of methanol. As isolated from aceto­nitrile the crystals are triclinic, space group P [Image: see text] with Z′ = 2. Crystals of form 2, which were isolated from methanol only are monoclinic, space group I2/a with Z′ = 1. The crystal packing in both structures is dominated by the formation of infinite –NH⋯O hydrogen-bonded chains through the carboxamide core.