Hexachlorobenzene

Hexachlorobenzene is an organic compound with the chemical formula C6Cl6. It belongs to the class of polychlorinated benzenes and is a colorless to pale yellow solid that is insoluble in water but readily soluble in organic solvents such as benzene and carbon disulfide. The molecule consists of a benzene ring with all six hydrogen atoms replaced by chlorine substituents.

The compound is produced mainly by the chlorination of benzene or tetrachlorobenzene using chlorine gas at high temperatures. Historically, hexachlorobenzene has been used as a fungicide against plant diseases, in the production of pigment precursors, and as a chemical intermediate for other chlorinated aromatic derivatives. However, its widespread application has declined due to environmental persistence and toxicity concerns.

Hexachlorobenzene is resistant to degradation and can accumulate in soils, sediments, and the tissues of organisms, especially in fatty tissues. It bioaccumulates in food chains, being detected in plant, fish, and mammalian fatty tissues. Its environmental transport is facilitated by its lipophilicity and low vapor pressure, which reduce volatilization but enhance long-range transport through soil particles and biota.

Toxicologically, hexachlorobenzene is associated with liver damage, immunosuppression, and endocrine disruption. Chronic exposure may lead to skin lesions and tumors. The United Nations' Stockholm Convention classifies it as a persistent organic pollutant, obligating parties to reduce or eliminate its production and use. Many national regulations restrict or ban hexachlorobenzene for agricultural and industrial purposes. Monitoring continues in environmental and food safety programs to detect its presence and mitigate human exposure.