Chloroform

Chloroform, also known as trichloromethane and methyl trichloride, is a solvent. It is also considered an environmental hazard.

History

Chloroform was discovered in July, 1831 by the American physician Samuel Guthrie,^[1] and independently a few months later by the French Jean-Baptiste Dumas.^[4]

In 1847, the Edinburgh obstetrician James Young Simpson first used chloroform for general anesthesia during childbirth. The use of chloroform during surgery expanded rapidly thereafter in Europe. In the United States, chloroform began to replace carcinogenic.

Production

Industrially, chloroform is produced by heating a mixture of chloromethane to progressively more chlorinated compounds.

CH₄ + Cl₂ → CH₃Cl + HCl

CH₃Cl + Cl₂ → CH₂Cl₂ + HCl

CH₂Cl₂ + Cl₂ → CHCl₃ + HCl

Chloroform undergoes further chlorination to give CCl₄:

CHCl₃ + Cl₂ → CCl₄ + HCl

The output of this process is a mixture of the four chloromethanes: chloromethane, dichloromethane, chloroform (trichloromethane), and carbon tetrachloride, which are then separated by distillation.^{[citation needed]}

Chloroform was first produced industrially by the reaction of chloral hydrate,^{[citation needed]} or from ordinary chloroform.^[5]

Inadvertent synthesis of chloroform

The haloform reaction can also occur inadvertently in domestic settings. Sodium hypochlorite solution (chlorine bleach) mixed with common household liquids such as isopropyl alcohol will all produce chloroform.

Uses

The major use of chloroform today is in the production of the R-22. However, as the Montreal Protocol takes effect, this use can be expected to decline as R-22 is replaced by refrigerants that are less liable to result in ozone depletion. In addition, it is used under research conditions to anesthetize mosquitoes for experiments, most frequently for the study of malaria. It is sometimes seen used in movies (e.g. Ace Ventura) and TV shows (e.g. Arrested Development) as an agent to knock out an unsuspecting victim.

Anesthetic

Chloroform was developed in the mid-1800s and was mainly used as an anesthetic. Inhaling chloroform vapors depressed the central nervous system of a patient, causing dizziness, fatigue and unconsciousness, allowing a doctor or barber to perform simple surgery or other painful operations.

As a solvent

Chloroform is a common solvent because it is relatively unreactive, miscible with most organic liquids, and conveniently volatile. Small amounts of chloroform are used as a acrylic glass (which is also known under the trade name 'Perspex').

As a reagent in organic synthesis

As a reagent, chloroform serves as a source of the dichlorocarbene CCl₂ group.^[6] It reacts with aqueous cyclopropane derivative.

Safety

As might be expected from its use as an phosgene) and to the kidneys, and some people develop sores when the skin is immersed in chloroform.

Animal studies have shown that miscarriages occur in rats and mice that have breathed air containing 30 to 300 ppm chloroform during pregnancy and also in rats that have ingested chloroform during pregnancy. Offspring of rats and mice that breathed chloroform during pregnancy have a higher incidence of birth defects, and abnormal sperm have been found in male mice that have breathed air containing 400 ppm chloroform for a few days. The effect of chloroform on reproduction in humans is unknown.

Chloroform once appeared in toothpastes, cough syrups, ointments, and other pharmaceuticals, but it has been banned in consumer products in the United States since 1976.^[9]

The National Toxicology Program's eleventh report on carcinogens^[10] implicates it as reasonably anticipated to be a human dichloromethane, have resulted in a substantial reduction of its use as a solvent.

During prolonged storage hazardous amounts of ethanol or amylene, but samples that have been recovered or dried no longer contain any stabilizer and caution must be taken. Suspicious bottles should be tested for phosgene. Filter-paper strips, wetted with 5% diphenylamine, 5% dimethylaminobenzaldehyde, and then dried, turn yellow in phosgene vapor.

Commonly used in DNA extractions and generally in conjunction with phenol to form a biolayer with extraction buffer (tris etc). DNA will form in the supernatant while protein and non soluble cell materials will precipitate between the buffer chloroform layers.

See also

• Haloalkane
• Halomethane
• Chloromethane
• Dichloromethane
• Carbon tetrachloride (Tetrachloromethane)
• Fluoroform
• Bromoform
• Iodoform

References