Crystal Structure of the Biocide Methylisothiazolinone

Methylisothiazolinone (MIT) is widely used as a biocide in numerous personal care products, glass-cleaning liquids, paints, and industrial applications. MIT and related isothiazolinones have attracted much attention for their allergenic properties such as contact dermatitis. Although the compound was first prepared in 1964 and has been widely used as a biocide since the 1970s, its crystal structure has so far not been reported. Here we report the solid state structure of MIT as determined by single crystal X-ray diffraction (SC-XRD) analysis of a crystal grown from the melt. MIT crystallizes as a layered structure with short C-H···O hydrogen bonding interactions within the sheets. The average distance between the sheets parallel to (1 0 2) is ca. 3.2 Å. The molecule exhibits a small C-S-N angle of 90.81(2)° and a methyl group that is slightly bent out of the plane of the planar five-membered ring. The sulfur atom does not undergo any significant intermolecular interactions.