dichloramine

Dichloramine, with the chemical formula NHCl2, is an inorganic chloramine derived from ammonia by replacing two hydrogen atoms with chlorine. It is part of the chloramine family, which also includes monochloramine (NH2Cl) and trichloramine (NCl3). In aqueous systems, dichloramine is a reactive, relatively short‑lived intermediate formed during the chlorination of ammonia-containing water.

Formation and occurrence: In water treated with chlorine, monochloramine forms first from ammonia and hypochlorous acid (HOCl); further oxidation of monochloramine with HOCl yields dichloramine, and additional oxidation can produce trichloramine. The relative amounts of these species depend on factors such as pH, temperature, and the chlorine-to-ammonia ratio. Dichloramine is typically more prevalent at moderate chlorine excess and near neutral pH.

Properties and stability: Dichloramine is less stable than monochloramine and tends to decompose under light, heat, or strongly oxidizing conditions. In water, it is soluble and can contribute to taste and odor concerns; it may also volatilize under certain conditions. As a chloramine intermediate, it plays a role in the broader chemistry of disinfection byproducts formed during chlorination.

Health and safety: Exposure to dichloramine can irritate the eyes, skin, and respiratory tract. In drinking water contexts, its formation is monitored because chloramine species can impact water taste, odor, and safety. Handling requires appropriate safety measures to avoid inhalation of vapors and contact with skin or eyes.

See also: Monochloramine, Trichloramine, Water disinfection.