Two polymorphic forms of the oxathiin systemic fungicide active carboxine

Area of Science:

• Solid-state chemistry
• Crystallography
• Materials science

Background:

• Polymorphism is crucial for compound properties and performance.
• Understanding crystal forms is essential for drug development and material design.
• The title compound, 6-methyl-N-phenyl-2,3-dihydro-1,4-oxathiine-5-carboxamide, is a molecule of interest.

Purpose of the Study:

• To investigate the polymorphic behavior of 6-methyl-N-phenyl-2,3-dihydro-1,4-oxathiine-5-carboxamide.
• To characterize the crystal structures of different polymorphic forms.
• To analyze the intermolecular interactions governing crystal packing.

Main Methods:

• A truncated polymorph screen using 12 solvents was performed on lyophilized material.
• Single crystal X-ray diffraction was used to determine the crystal structures.
• Analysis of crystal packing and hydrogen bonding was conducted.

Main Results:

• Two polymorphic crystal forms (Form 1 and Form 2) were successfully isolated.
• Form 1 crystallized in the triclinic space group P with Z'=2 (from acetonitrile).
• Form 2 crystallized in the monoclinic space group I2/a with Z'=1 (from methanol).
• Both crystal structures exhibit infinite -NH⋯O hydrogen-bonded chains formed by the carboxamide core.

Conclusions:

• The study successfully identified and characterized two distinct polymorphic forms of the title compound.
• The crystal packing is predominantly dictated by carboxamide-based hydrogen bonding, forming infinite chains.
• This detailed crystallographic analysis provides fundamental insights into the solid-state behavior of this compound.