haloform

Haloforms are a class of organohalogen compounds with the general formula CHX3, where X is a halogen (typically chlorine, bromine or iodine). The best-known members are chloroform (CHCl3), bromoform (CHBr3) and iodoform (CHI3). These compounds are volatile and relatively nonpolar, with chloroform and bromoform existing as liquids at room temperature and iodoform as a pale yellow solid.

Haloforms appear in various chemical contexts, including as byproducts of oxidation and chlorination processes and in certain laboratory reactions. A central theme in haloform chemistry is the haloform reaction, in which a methyl ketone or an ethanol-like substrate undergoes three halogenations in the presence of base, followed by cleavage to yield the haloform CHX3 and a carboxylate. Typical reagents are halogen (Cl2, Br2, or I2) in a basic medium such as sodium hydroxide. The reaction provides a useful diagnostic test for methyl ketones and for alcohols that can be oxidized to methyl ketones.

Applications and significance include analytical use, where the haloform test detects methyl ketones and related substrates. In industry and public health, haloforms—especially chloroform—are monitored because they can be toxic and, in some contexts, carcinogenic. Chloroform is restricted in many applications, and haloforms can form as disinfection byproducts during water treatment and other chlorination processes, prompting regulatory controls and safety considerations. See also relationships to trihalomethanes and haloalkane chemistry.