Chloroacetic acid
Encyclopedia
Chloroacetic acid, industrially known as monochloroacetic acid (MCA) is the organochlorine compound with the formula ClCH2CO2H. This carboxylic acid
is a useful building-block in organic synthesis
.
.
of acetic acid
:
Acetic anhydride
serves as a catalyst for this reaction.
The other main industrial route to chloroacetic acid is hydrolysis
of trichloroethylene
using sulfuric acid
as a catalyst.
The hydrolysis method produces a highly pure product, which can be important since mono-, di-, and trichloroacetic acids are difficult to separate by distillation. Approximately, 420,000,000 kg/y are produced globally.
with chloroacetic acid, followed by decarboxylation
of the resulting ether
, producing benzofuran
.
In industry, chloroacetic acid is used in the production of a wide variety of useful compounds, e.g., drugs, dyes, pesticides. Most reactions taking advantage of the high reactivity of the C–Cl bond. It is the precursor to the herbicide glyphosate. The herbicides MCPA
(2-methyl-4-chlorophenoxyacetic acid) and dimethoate
are prepared by alkylation with chloroacetic acid. Chloroacetic acid is converted to chloroacetyl chloride
, a precursor to adrenaline (epinephrine). Displacement of chloride by sulfide gives thioglycolic acid
, which is used as a stabilizer in PVC
and a component in some cosmetics
.
In its largest-scale application, chloroacetic acid is used to prepare the thickening agent carboxymethyl cellulose
and carboxymethyl starch
.
and related halocarbons, chloroacetic acid is a potentially dangerous alkylating agent. The for rats is 76 mg/kg.
Chloroacetic acid easily penetrates skin and mucous membranes and interferes with cellular energy production. Initial dermal exposure to high concentrations (e.g., 80% solution) may not appear very damaging at first, however systemic poisoning may present within hours. Exposure can be fatal if greater than 6% body surface area is exposed to chloroacetic acid. The sodium salt does not penetrate the skin as well as the acid but can be as damaging given a longer duration and greater surface area of exposure.
Upon one's exposure to chloroacetic acid, immediate decontamination should be commenced by rinsing the affected area with water or bicarbonate solution in order to neutralize the acid and prevent further skin absorption.
The antidote of chloroacetic acid poisoning is sodium dichloroacetate (50 mg/kg IV over 10 mins, repeated in 2h; double dosage if hemodialysis is performed).
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...
is a useful building-block in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
.
Production
The production of chloroacetic acid was 706,000 tonnes/year in 2010, of which over half is produced in China. Other countries with significant production capacity are Germany (105,000), the Netherlands (100,000), India (>65,000), and the United States (55,000). The world's largest producer is Akzo NobelAkzo Nobel
Akzo Nobel N.V., trading as AkzoNobel, is a Dutch multinational, active in the fields of decorative paints, performance coatings and specialty chemicals. Headquartered in Amsterdam, the company has activities in more than 80 countries, and employs approximately 55,000 people. Sales in 2010 were EUR...
.
Processes
Chloroacetic acid is prepared industrially via two routes. The predominant method involves chlorinationChlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
of acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
:
- + → +
Acetic anhydride
Acetic anhydride
Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula 2O. Commonly abbreviated Ac2O, it is the simplest isolatable acid anhydride and is a widely used reagent in organic synthesis...
serves as a catalyst for this reaction.
The other main industrial route to chloroacetic acid is hydrolysis
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
of trichloroethylene
Trichloroethylene
The chemical compound trichloroethylene is a chlorinated hydrocarbon commonly used as an industrial solvent. It is a clear non-flammable liquid with a sweet smell. It should not be confused with the similar 1,1,1-trichloroethane, which is commonly known as chlorothene.The IUPAC name is...
using sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
as a catalyst.
- + 2 → + 2
The hydrolysis method produces a highly pure product, which can be important since mono-, di-, and trichloroacetic acids are difficult to separate by distillation. Approximately, 420,000,000 kg/y are produced globally.
Reactivity and uses
Illustrative of its usefulness in organic chemistry is the O-alkylation of salicylaldehydeSalicylaldehyde
Salicylaldehyde is the chemical compound with the formula C6H4CHO-2-OH. Along with 3-hydroxybenzaldehyde and 4-hydroxybenzaldehyde, it is one of the three isomers of hydroxybenzaldehyde. This colorless oily liquid has a bitter almond odor at higher concentration and a characteristic buckwheat...
with chloroacetic acid, followed by decarboxylation
Decarboxylation
Decarboxylation is a chemical reaction that releases carbon dioxide . Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain. The reverse process, which is the first chemical step in photosynthesis, is called carbonation, the addition of CO2 to...
of the resulting ether
Ether
Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...
, producing benzofuran
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 is a benzofuran derivative that occurs in several...
.
In industry, chloroacetic acid is used in the production of a wide variety of useful compounds, e.g., drugs, dyes, pesticides. Most reactions taking advantage of the high reactivity of the C–Cl bond. It is the precursor to the herbicide glyphosate. The herbicides MCPA
MCPA
MCPA or 2-methyl-4-chlorophenoxyacetic acid is a powerful, selective, widely-used phenoxy herbicide. The pure compound is a brown-colored powder.-History:...
(2-methyl-4-chlorophenoxyacetic acid) and dimethoate
Dimethoate
Dimethoate is a widely used organophosphate insecticide used to kill insects on contact. It was patented and introduced in the 1950s by American Cyanamid. Like other organophosphates, dimethoate is an anticholinesterase which disables cholinesterase, an enzyme essential for central nervous system...
are prepared by alkylation with chloroacetic acid. Chloroacetic acid is converted to chloroacetyl chloride
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 chloride, or the addition of chlorine to ketene...
, a precursor to adrenaline (epinephrine). Displacement of chloride by sulfide gives thioglycolic acid
Thioglycolic acid
Thioglycolic acid is the organic compound HSCH2CO2H. It contains both a thiol and a carboxylic acid. It is a clear liquid with a strong unpleasant odor...
, which is used as a stabilizer in PVC
PVC
Polyvinyl chloride is a plastic.PVC may also refer to:*Param Vir Chakra, India's highest military honor*Peripheral venous catheter, a small, flexible tube placed into a peripheral vein in order to administer medication or fluids...
and a component in some cosmetics
Cosmetics
Cosmetics are substances used to enhance the appearance or odor of the human body. Cosmetics include skin-care creams, lotions, powders, perfumes, lipsticks, fingernail and toe nail polish, eye and facial makeup, towelettes, permanent waves, colored contact lenses, hair colors, hair sprays and...
.
In its largest-scale application, chloroacetic acid is used to prepare the thickening agent carboxymethyl cellulose
Carboxymethyl cellulose
Carboxymethyl cellulose or cellulose gum is a cellulose derivative with carboxymethyl groups bound to some of the hydroxyl groups of the glucopyranose monomers that make up the cellulose backbone...
and carboxymethyl starch
Modified starch
Modified starch, also called starch derivatives, are prepared by physically, enzymatically, or chemically treating native starch, thereby changing the properties of the starch. Modified starches are used in practically all starch applications, such as in food products as a thickening agent,...
.
Safety
Like other chloroacetic acidsChloroacetic acids
In organic chemistry, the chloroacetic acids are three related chlorocarbon carboxylic acids:* Chloroacetic acid , CH2ClCOOH* Dichloroacetic acid , CHCl2COOH...
and related halocarbons, chloroacetic acid is a potentially dangerous alkylating agent. The for rats is 76 mg/kg.
Chloroacetic acid easily penetrates skin and mucous membranes and interferes with cellular energy production. Initial dermal exposure to high concentrations (e.g., 80% solution) may not appear very damaging at first, however systemic poisoning may present within hours. Exposure can be fatal if greater than 6% body surface area is exposed to chloroacetic acid. The sodium salt does not penetrate the skin as well as the acid but can be as damaging given a longer duration and greater surface area of exposure.
Upon one's exposure to chloroacetic acid, immediate decontamination should be commenced by rinsing the affected area with water or bicarbonate solution in order to neutralize the acid and prevent further skin absorption.
The antidote of chloroacetic acid poisoning is sodium dichloroacetate (50 mg/kg IV over 10 mins, repeated in 2h; double dosage if hemodialysis is performed).
See also
- Chloroacetic acidsChloroacetic acidsIn organic chemistry, the chloroacetic acids are three related chlorocarbon carboxylic acids:* Chloroacetic acid , CH2ClCOOH* Dichloroacetic acid , CHCl2COOH...
- Dichloroacetic acidDichloroacetic acidDichloroacetic acid, often abbreviated DCA, is the chemical compound with formula . It is an acid, an analogue of acetic acid, in which two of the three hydrogen atoms of the methyl group have been replaced by chlorine atoms. The salts and esters of dichloroacetic acid are called dichloroacetates...
- Trichloroacetic acidTrichloroacetic acidTrichloroacetic acid is an analogue of acetic acid in which the three hydrogen atoms of the methyl group have all been replaced by chlorine atoms....
- Chloracetyl chloride