Chloroform (trichloromethane): properties, uses, history and safety

Physical and chemical characteristics

Chloroform is heavier than water and only sparingly soluble in it; it evaporates readily at room temperature. It is relatively non-flammable under normal conditions, but it can react or degrade to form hazardous byproducts if exposed to air and light over time. In structure it contains one carbon atom bonded to one hydrogen and three chlorine atoms (hence "tri"chloromethane). Its reactivity makes it useful in many organic reactions and separations.

History and medical use

In the 19th century chloroform became widely used as a general anesthetic and was celebrated for its rapid induction of unconsciousness. Its use was popular in surgery and obstetrics for a time, but concerns about unpredictable toxicity, including cardiac complications and sudden death, led to its abandonment as a routine anesthetic. A readable historical perspective notes this medical role and its eventual replacement by safer agents; see an overview on historical anesthetics.

Industrial production and applications

Today chloroform is produced industrially, often as a result of controlled chlorination reactions, and has several applications. It serves as a solvent in laboratories and industry — for example in extraction procedures and certain synthetic steps — and as an intermediate in manufacture of other chemicals. One notable industrial link is its role as a precursor or intermediate in processes related to polytetrafluoroethylene (PTFE), commercially known as Teflon. Chloroform's solvent uses are commonly referenced in chemical supply information about solvents.

Uses, distinctions and examples

• Common laboratory use: organic extractions, reagent carrier and chromatography solvent.
• Industrial intermediates: feedstock for the synthesis of other chlorinated compounds and fluorochemical precursors.
• Distinct from related chemicals such as carbon tetrachloride and methylene chloride in toxicity profile and reactivity; it is properly called trichloromethane to distinguish it from other chlorinated methanes (compound comparisons).

Health, environmental and regulatory considerations

Chloroform is a central nervous system depressant; acute exposure can cause dizziness, nausea and loss of consciousness. Chronic or high-level exposure has been associated with liver and kidney damage and is treated cautiously by regulatory agencies as a potential carcinogen. It can also degrade to form phosgene and other harmful byproducts if stored improperly, so stabilized grades and controlled storage are standard practice. Use is subject to workplace controls, handling precautions and environmental regulations in many jurisdictions.

For topical chemical summaries and safety guidelines see general references on solvents and anesthetic history: chemical summaries, organic compound guides, and industry notes on solvents and intermediates solvent information, PTFE production. Further background on historical medical use is available here.