Captan

Captan, with the chemical formula \(C_9H_8Cl_3NO_2S\), is a dicarboximide fungicide that is used on a variety of crops, including fruits and ornamentals[3]. It is a white, odorless, crystalline solid when pure, but the technical grade is a cream to yellow powder with a strong odor[2]. The molecular weight of captan is 300.6 g/mol[4].

Chemical Properties

• Solubility: Captan has a low aqueous solubility and is practically insoluble in water[3][4].
• Vapor Pressure: It has a vapor pressure of less than 0.00001 mmHg at 77°F (25°C)[4][5].
• Melting Point: The melting point of pure captan is 352°F (178°C), while the technical grade (90-95% pure) has a melting point range of 158-170°C[7].
• Stability: Captan is stable at room temperature but hydrolyzes in aqueous solutions, with the rate of hydrolysis depending on the pH. It decomposes rapidly in alkaline solutions[7].
• Reactivity: It may react with water to form hydrogen chloride gas and is corrosive to metals in the presence of moisture[2]. Captan is not compatible with strong alkalies, tetraethyl pyrophosphate, oil sprays, and parathion[2].
• Partition Coefficient: The log octanol/water partition coefficient (log Kow) is about 2.35 to 2.54[4].

Environmental and Health Impact

• Toxicity: Captan has a low mammalian toxicity but is considered to be an eye and skin irritant. It is also classified as a Group B2, probable human carcinogen by the EPA[4].
• Environmental Fate: It is not generally expected to leach to groundwater and is not usually persistent in soil or water systems[3].
• Ecotoxicity: Captan has a low to moderate ecotoxicity for most aquatic and terrestrial species[3].

Uses

Captan is predominantly used in agriculture as a fungicide on a wide variety of fruits, vegetables, and ornamentals. It is also used in seed treatment, cosmetics, pharmaceuticals, oil-based paints, lacquers, wallpaper paste, plasticizers, polyethylene, vinyl, rubber stabilizers, and textiles[4].

Safety Measures

In case of spills or leaks, it is recommended to moisten spilled material or use a HEPA-filter vacuum for clean-up. Absorb liquids in vermiculite, dry sand, earth, or a similar material and deposit in sealed containers[2]. Protective equipment such as gloves, coveralls, and respirators may be necessary when handling captan[2].

Fire Hazard

Captan does not burn in its pure form, but it may be dissolved in a liquid carrier that could be flammable or combustible. In case of fire, poisonous gases such as sulfur oxides, nitrogen oxides, hydrogen chloride, and phosgene can be produced[2].

Citations:

[1] https://pubchem.ncbi.nlm.nih.gov/compound/Captan

[2] https://nj.gov/health/eoh/rtkweb/documents/fs/0339.pdf

[3] http://sitem.herts.ac.uk/aeru/ppdb/en/Reports/114.htm

[4] https://www.epa.gov/sites/default/files/2016-09/documents/captan.pdf

[5] https://cameochemicals.noaa.gov/chemical/2803

[6] http://extoxnet.orst.edu/pips/captan.htm

[7] https://inchem.org/documents/pims/chemical/pim098.htm

[8] https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/captan