Trichloroacetic acid (TCA; TCAA; also known as trichloroethanoic acid) is an analogue of

acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main componen ...

in which the three

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-to ...

atoms of the

methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in ...

group have all been replaced by

chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...

atoms.

Salts In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively c ...

and

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ...

s of trichloroacetic acid are called trichloroacetates.

Synthesis

It is prepared by the reaction of chlorine with

in the presence of a suitable

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

such as

red phosphorus Elemental phosphorus can exist in several allotropes, the most common of which are white and red solids. Solid violet and black allotropes are also known. Gaseous phosphorus exists as diphosphorus and atomic phosphorus. White phosphorus Whit ...

. This reaction is

Hell–Volhard–Zelinsky halogenation The Hell–Volhard–Zelinsky halogenation reaction is a chemical transformation that involves the halogenation of a carboxylic acid at the α carbon. For this reaction to occur the α carbon must bear at least one proton. The reaction is named ...

. : + 3 → + 3 Another route to trichloroacetic acid is the oxidation of trichloroacetaldehyde.

Use

It is widely used in

biochemistry Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology and ...

for the precipitation of macromolecules, such as

proteins Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

, DNA, and RNA. TCA and DCA are both used in cosmetic treatments (such as chemical peels and tattoo removal) and as

topical medication A topical medication is a medication that is applied to a particular place on or in the body. Most often topical medication means application to body surfaces such as the skin or mucous membranes to treat ailments via a large range of classes ...

for

chemoablation Ablation ( la, ablatio – removal) is removal or destruction of something from an object by vaporization, chipping, erosive processes or by other means. Examples of ablative materials are described below, and include spacecraft material for a ...

warts Warts are typically small, rough, hard growths that are similar in color to the rest of the skin. They typically do not result in other symptoms, except when on the bottom of the feet, where they may be painful. While they usually occur on the ...

, including

genital warts Genital warts are a sexually transmitted infection caused by certain types of human papillomavirus (HPV). They are generally pink in color and project out from the surface of the skin. Usually they cause few symptoms, but can occasionally be pai ...

. It can kill normal cells as well. It is considered safe for use for this purpose during pregnancy. The sodium salt (

sodium trichloroacetate Sodium trichloroacetate is a chemical compound with a formula of CCl3CO2Na. It is used to increase sensitivity and precision during transcript mapping. It was previously used as an herbicide starting in the 1950s but regulators removed it from th ...

) was used as an

herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page f ...

starting in the 1950s but regulators removed it from the market in the late 1980s and early 1990s.

Environmental and health concerns

According to the European Chemicals Agency, "This substance causes severe skin burns and eye damage, is very toxic to aquatic life and has long lasting toxic effects." Trichloroacetic acid was placed on the California Proposition 65 List in 2013 "as a chemical known to the state to cause cancer".

History

The discovery of trichloroacetic acid by

Jean-Baptiste Dumas Jean Baptiste André Dumas (14 July 180010 April 1884) was a French chemist, best known for his works on organic analysis and synthesis, as well as the determination of atomic weights (relative atomic masses) and molecular weights by measuring ...

in 1839 delivered a striking example to the slowly evolving theory of organic radicals and valences. The theory was contrary to the beliefs of Jöns Jakob Berzelius, starting a long dispute between Dumas and Berzelius.

Popular Culture

In the 1958 film,

The Blob ''The Blob'' is a 1958 American science fiction horror film directed by Irvin Yeaworth, and written by Kay Linaker and Theodore Simonson. It stars Steve McQueen (in his first feature film leading role) and Aneta Corsaut and co-stars Earl Rowe ...

, a bottle of trichloroacetic acid is tossed at the Blob in a futile attempt to fend it off.

References

External links

*
CDC - NIOSH Pocket Guide to Chemical Hazards
{{DEFAULTSORT:Trichloroacetic Acid Acetic acids IARC Group 2B carcinogens Trichloromethyl compounds Organic compounds with 2 carbon atoms