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Chloroform

physical science Maturity 11-13 Next article →

Chloroform, also known as trichloromethane (TCM), is a colorless, dense, and volatile liquid. It has a distinctively sweet smell and belongs to a group of chemicals called organochlorides. Because it is an organochloride, its structure is built from carbon and chlorine. Chloroform is highly useful in modern industry as a chemical precursor. This means it is a starting material used to create other substances. It is also a versatile solvent, which is a liquid used to dissolve other materials.

Chickamauga 2009, Chloroform
Chickamauga 2009, Chloroform

The molecular structure of chloroform is quite specific. It follows a tetrahedral molecular geometry, which means its atoms are arranged in a shape similar to a four-sided pyramid. You can visualize the molecule as a methane molecule where three of the hydrogen atoms have been replaced by three chlorine atoms. This leaves only one hydrogen atom remaining. The name "chloroform" is actually a portmanteau. It combines the words "terchloride," meaning a trichloride, and "formyle," which was an old name for a specific part of formic acid.

Industrial production of chloroform happens through a process called free radical halogenation. To start, engineers heat a mixture of chlorine and either methane or methyl chloride. This reaction occurs at very high temperatures, specifically between 400 and 500 degrees Celsius. As the chemicals react, they transform into a mixture of four different chloromethanes. These include chloromethane, methylene chloride, trichloromethane, and carbon tetrachloride. To get pure chloroform, workers use a process called distillation to separate it from the other three substances. On a smaller scale, chloroform can also be made through the haloform reaction between acetone and sodium hypochlorite.

The history of its discovery is filled with many different scientists. In 1830, a German pharmacist named Moldenhawer produced it by mixing ethanol with chlorinated lime, though he thought it was something else. In 1831, an American physician named Samuel Guthrie also produced it and noticed its effects. However, it was the French chemist Jean-Baptiste Dumas who truly defined it. In 1834, Dumas determined the correct empirical formula and gave the substance the name "chloroform." By the year 1895, the production of this chemical had grown significantly, with Britain producing about 750,000 doses a week using the Liebig procedure.

Chloroform played a massive role in the history of medicine as an inhalational anesthetic. In 1842, Robert Mortimer Glover discovered its anesthetic qualities through experiments on laboratory animals. In 1847, a Scottish obstetrician named James Y. Simpson demonstrated its use in humans. This helped make chloroform very popular in medical settings. However, the substance was quite dangerous. Accidental overdoses caused many deaths, including the death of a 15-year-old girl named Hannah Greener in 1848. To make the process safer, John Snow developed an inhaler in 1848 to regulate the dosage. Later, Joseph Thomas Clover invented a more controllable apparatus in 1862.

James Young Simpson chloroform
James Young Simpson chloroform

Despite its medical history, chloroform is still vital to modern manufacturing. One of its most important uses is reacting with hydrogen fluoride to create monochlorodifluoromethane (HCFC-22). This chemical is a key precursor for making polytetrafluoroethylene, which is commonly known as Teflon. This material is used to make non-stick coatings. Chloroform is also used to produce refrigerants. While it has a low global warming potential of only 31, it is mostly used to create other cooling agents rather than being used directly in consumer products. It is also used in the production of various fluoropolymers.

Beyond making plastics, chloroform serves many other industrial purposes. Because the hydrogen atom in the molecule can participate in hydrogen bonding, it is an excellent solvent. It is used worldwide in pesticide formulations and to dissolve substances like rubber, waxes, and resins. It even finds use in fire extinguishers and as a grain fumigant. In scientific laboratories, a special version called deuterochloroform is used. This version contains a deuterium atom instead of a standard hydrogen atom. Scientists use it as a solvent in NMR spectroscopy, a tool used to study the structure of molecules. It can even be formed accidentally in homes if chlorine bleach is mixed with liquids like acetone or isopropyl alcohol.

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File:Chickamauga 2009, Chloroform.jpg
Chickamauga 2009, Chloroform.jpg
File:James Young Simpson chloroform.png
James Young Simpson chloroform.png
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