Chloroacetic acid, industrially known as monochloroacetic acid (MCA), is the
organochlorine compound
An organochloride, organochlorine compound, chlorocarbon, or chlorinated hydrocarbon is an organic compound containing at least one covalent bond, covalently bonded atom of chlorine. The chloroalkane class (alkanes with one or more hydrogens subst ...
with the formula ClCH
2CO
2H. This
carboxylic acid
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic ...
is a useful building block in
organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...
. It is a colorless solid. Related compounds are
dichloroacetic acid
Dichloroacetic acid (DCA), sometimes called bichloroacetic acid (BCA), is the chemical compound with formula . It is an acid, an analogue of acetic acid, in which 2 of the 3 hydrogen atoms of the methyl group have been replaced by chlorine atoms. ...
and
trichloroacetic acid
Trichloroacetic acid (TCA; TCAA; also known as trichloroethanoic acid) is an analogue of acetic acid in which the three hydrogen atoms of the methyl group have all been replaced by chlorine atoms. Salts and esters of trichloroacetic acid are calle ...
.
Production
Chloroacetic acid was first prepared (in impure form) by the French chemist Félix LeBlanc (1813–1886) in 1843 by chlorinating acetic acid in the presence of sunlight, and in 1857 (in pure form) by the German chemist Reinhold Hoffmann (1831–1919) by refluxing
glacial 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 component ...
in the presence of chlorine and sunlight, and then by the French chemist
Charles Adolphe Wurtz
Charles Adolphe Wurtz (; 26 November 181710 May 1884) was an Alsatian French chemist. He is best remembered for his decades-long advocacy for the atomic theory and for ideas about the structures of chemical compounds, against the skeptical opinio ...
by hydrolysis of
chloroacetyl chloride
Chloroacetyl chloride is a chlorinated acyl chloride. It is a bifunctional compound, making it a useful building block chemical.
Production
Industrially, it is produced by the carbonylation of methylene chloride, oxidation of vinylidene chlorid ...
(ClCH
2COCl), also in 1857.
Chloroacetic acid is prepared industrially by two routes. The predominant method involves
chlorination Chlorination may refer to:
* Chlorination reaction
In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transform ...
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 component ...
, with
acetic anhydride
Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula (CH3CO)2O. Commonly abbreviated Ac2O, it is the simplest isolable anhydride of a carboxylic acid and is widely used as a reagent in organic synthesis. It is a col ...
as a
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 ...
:
: + → +
This route suffers from the production of
dichloroacetic acid
Dichloroacetic acid (DCA), sometimes called bichloroacetic acid (BCA), is the chemical compound with formula . It is an acid, an analogue of acetic acid, in which 2 of the 3 hydrogen atoms of the methyl group have been replaced by chlorine atoms. ...
and
trichloroacetic acid
Trichloroacetic acid (TCA; TCAA; also known as trichloroethanoic acid) is an analogue of acetic acid in which the three hydrogen atoms of the methyl group have all been replaced by chlorine atoms. Salts and esters of trichloroacetic acid are calle ...
as impurities, which are difficult to separate by
distillation
Distillation, or classical distillation, is the process of separation process, separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distilla ...
:
: + 2 → + 2
: + 3 → + 3
The second method entails hydrolysis of
trichloroethylene
The chemical compound trichloroethylene is a halocarbon commonly used as an industrial solvent. It is a clear, colourless non-flammable liquid with a chloroform-like sweet smell. It should not be confused with the similar 1,1,1-trichloroethane, ...
:
: + 2 → + 2
The hydrolysis is conducted at 130–140 °C in a concentrated (at least 75%) solution of sulfuric acid. This method produces a highly pure product, unlike the halogenation route. However, the significant quantities of HCl released have led to the increased popularity of the halogenation route. Approximately 420,000 tonnes are produced globally per year.
Uses and reactions
Most reactions take advantage of the high reactivity of the C–Cl bond.
In its largest-scale application, chloroacetic acid is used to prepare the thickening agent
carboxymethyl cellulose
Carboxymethyl cellulose (CMC) or cellulose gum is a cellulose derivative with carboxymethyl groups (-CH2-COOH) bound to some of the hydroxyl groups of the glucopyranose monomers that make up the cellulose backbone. It is often used as its sodi ...
and
carboxymethyl starch.
Chloroacetic acid is also used in the production of
phenoxy herbicide
Phenoxy herbicides (or "phenoxies") are two families of chemicals that have been developed as commercially important herbicides, widely used in agriculture. They share the part structure of phenoxyacetic acid. Auxins
The first group to be discover ...
s by etherification with chlorophenols. In this way
2-methyl-4-chlorophenoxyacetic acid (MCPA),
2,4-dichlorophenoxyacetic acid, and
2,4,5-trichlorophenoxyacetic acid (2,4,5-T) are produced. It is the precursor to the herbicide
glyphosate
Glyphosate (IUPAC name: ''N''-(phosphonomethyl)glycine) is a broad-spectrum Herbicide, systemic herbicide and Crop desiccation, crop desiccant. It is an organophosphorus compound, specifically a phosphonate, which acts by inhibiting the plan ...
and
dimethoate
Dimethoate is a widely used organophosphate insecticide and acaricide. It was patented and introduced in the 1950s by American Cyanamid. Like other organophosphates, dimethoate is an acetylcholinesterase inhibitor which disables cholinesterase, an ...
. Chloroacetic acid is converted to
chloroacetyl chloride
Chloroacetyl chloride is a chlorinated acyl chloride. It is a bifunctional compound, making it a useful building block chemical.
Production
Industrially, it is produced by the carbonylation of methylene chloride, oxidation of vinylidene chlorid ...
, a precursor to
adrenaline
Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands and ...
(epinephrine). Displacement of chloride by sulfide gives
thioglycolic acid
Thioglycolic acid (TGA) is the organic compound HSCH2CO2H. TGA is often called mercaptoacetic acid (MAA). It contains both a thiol ( mercaptan) and carboxylic acid functional groups. It is a colorless liquid with a strongly unpleasant odor. TGA i ...
, which is used as a stabilizer in
PVC and a component in some
cosmetics
Cosmetics are constituted mixtures of chemical compounds derived from either natural sources, or synthetically created ones. Cosmetics have various purposes. Those designed for personal care and skin care can be used to cleanse or protect ...
.
[
Illustrative of its usefulness in organic chemistry is the ''O''-alkylation of ]salicylaldehyde
Salicylic aldehyde (2-hydroxybenzaldehyde) is the organic compound with the formula (C7 H6 O2) C6H4CHO-2-OH. Along with 3-hydroxybenzaldehyde and 4-hydroxybenzaldehyde, it is one of the three isomers of hydroxybenzaldehyde. This colorless oil ...
with chloroacetic acid, followed by decarboxylation of the resulting ether
In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be c ...
, producing benzofuran
Benzofuran is the heterocyclic compound consisting of fused benzene and furan rings. This colourless liquid is a component of coal tar. Benzofuran is the "parent" of many related compounds with more complex structures. For example, psoralen i ...
.
Safety
Like other chloroacetic acids
In organic chemistry, the chloroacetic acids (systematic name chloroethanoic acids) are three related chlorocarbon carboxylic acids:
* Chloroacetic acid (chloroethanoic acid), CH2ClCOOH
* Dichloroacetic acid (dichloroethanoic acid; bichloroacetic ...
and related halocarbons, chloroacetic acid is a hazardous alkylating agent
Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effectin ...
. The for rats is 76 mg/kg.[
It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. ]Emergency Planning and Community Right-to-Know Act
The Emergency Planning and Community Right-to-Know Act of 1986 is a United States federal law passed by the 99th United States Congress located at Title 42, Chapter 116 of the U.S. Code, concerned with emergency response preparedness.
On October ...
(42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.
See also
*Fluoroacetic acid
Fluoroacetic acid is a organofluorine compound with formula CH2FCO2H. It is a colorless solid that is noted for its relatively high toxicity. The conjugate base, fluoroacetate occurs naturally in at least 40 plants in Australia, Brazil, and Afric ...
References
External links
*
*
{{DEFAULTSORT:Chloroacetic Acid
Acetic acids
Alkylating agents
Organochlorides
Organic compounds with 2 carbon atoms