chloroform

chloroform
Name	Chloroform
IUPACName	Trichloromethane
OtherNames	Formyl trichloride, Methane trichloride

chloroform is a dense, colorless, sweet-smelling liquid belonging to the class of haloalkanes. Its chemical formula is CHCl₃, and it is produced on an industrial scale primarily as a precursor to polytetrafluoroethylene and refrigerants. Historically, it gained widespread fame as one of the first general anesthetics, revolutionizing surgery in the 19th century, but its medical use has been abandoned due to significant toxicity. Today, its applications are largely restricted to industrial processes and as a solvent in chemical laboratories.

Properties

Chloroform is a trihalomethane, characterized by its relatively high density and low solubility in water. It is miscible with many organic solvents such as diethyl ether and ethanol. The molecule has a tetrahedral geometry, and it is not flammable under normal conditions. It slowly undergoes decomposition in air when exposed to light and oxygen, forming toxic phosgene and hydrogen chloride, a process inhibited by storing it with stabilizers like ethanol. Its physical properties, including its boiling point and vapor pressure, make it a volatile compound at room temperature.

Production

The primary industrial method for synthesizing chloroform is the chlorination of methane or chloromethane. This process, often conducted at temperatures between 400–500 °C, yields a mixture of products including methylene chloride and carbon tetrachloride, from which it is separated by distillation. A historical laboratory-scale preparation involved the haloform reaction between acetone or ethanol and sodium hypochlorite (bleach). Modern production is dominated by large-scale chemical manufacturers, with significant historical operations conducted by companies like Imperial Chemical Industries and Dow Chemical Company.

Uses

Its most famous historical use was as an inhalation anesthetic, notably popularized by figures such as James Young Simpson in Edinburgh. Industrially, it serves as a key intermediate in the production of HCFC-22, a refrigerant and precursor to polytetrafluoroethylene (Teflon). In laboratory settings, it is a common solvent for lipids, alkaloids, and iodine, and is used in extraction processes and spectroscopy, particularly NMR spectroscopy. It has also been used in the past in formulations like cough syrup, but such consumer applications have been discontinued.

Safety and toxicity

Exposure poses serious health risks, primarily causing central nervous system depression, and damage to the liver and kidneys. Inhalation of high concentrations can rapidly lead to respiratory failure and cardiac arrhythmia, a condition historically termed "chloroform syncope." It is classified as a probable human carcinogen by agencies like the International Agency for Research on Cancer and the United States Environmental Protection Agency. Safe handling requires the use of fume hoods and personal protective equipment, and its transport is regulated under guidelines from the Department of Transportation.

History

Chloroform was independently discovered in 1831 by the American physician Samuel Guthrie and the French chemist Eugène Soubeiran, with its formula determined shortly after by the renowned French chemist Jean-Baptiste Dumas. Its anesthetic properties were first demonstrated publicly in 1847 by James Young Simpson, leading to its rapid adoption in surgical procedures, including use during childbirth for Queen Victoria. Its popularity waned in the early 20th century with the introduction of safer agents like diethyl ether and halothane, and its non-anesthetic uses expanded through the work of industrial chemists at BASF and DuPont.

Environmental impact

It is a volatile organic compound that can contaminate groundwater and atmosphere, often formed as a byproduct of water chlorination at treatment facilities. In the atmosphere, it contributes to stratospheric ozone depletion, though its ozone-depleting potential is lower than that of chlorofluorocarbons. Its environmental persistence and toxicity have led to strict regulations on its release under international agreements like the Montreal Protocol and national laws such as the Clean Air Act in the United States. Remediation of contaminated sites may involve advanced oxidation processes or bioremediation techniques.

Category:Anesthetics Category:Chloroalkanes Category:Solvents