Chlorothalonil is a colourless, odourless, crystalline solid with a melting point of 250°C and a vapour pressure of 7.63 × 10-5 Pa (5.72 × 10-7 mmHg) at 25°C. It has low water solubility (0.6-1.2 mg/litre at 25°C) and an octanol/water partition coefficient (log Kow) of 2.882. It is hydrolysed in water slowly at pH 9 but is stable at pH 7 or below (at 25°C). Chlorothalonil has been produced commercially since 1969 by chlorination of isophthalonitrile or by treatment of tetrachloroisophthaloyl amide with phosphorus oxychloride. It is a fungicide with a broad spectrum of activity used mainly in agriculture but also on turf, lawns and ornamental plants.