Chloroacetic acid

Chloroacetic acid
IUPAC name Chloroacetic acid
Systematic name Chloroethanoic acid
Identifiers
CAS number	79-11-8 Y
ChemSpider	10772140 Y
UNII	5GD84Y125G Y
KEGG	D07677 Y
ChEBI	CHEBI:27869 Y
ChEMBL	CHEMBL14090 Y
RTECS number	AF8575000
Jmol-3D images	Image 1
SMILES ClCC(O)=O
InChI InChI=1S/C2H3ClO2/c3-1-2(4)5/h1H2,(H,4,5) Y Key: FOCAUTSVDIKZOP-UHFFFAOYSA-N Y InChI=1/C2H3ClO2/c3-1-2(4)5/h1H2,(H,4,5) Key: FOCAUTSVDIKZOP-UHFFFAOYAR
Properties
Molecular formula	C2H3ClO2
Molar mass	94.5 g mol−1
Appearance	Colorless or white crystals
Density	1.58 g cm−3, solid
Melting point	63 °C, 336 K, 145 °F
Boiling point	189.3 °C, 462.5 K, 372.7 °F
Solubility in water	85.8 g/100mL (25 °C)
Acidity (pKa)	2.86[1]
Hazards
MSDS	External MSDS
R-phrases	R25 R34 R50
S-phrases	S23 S37 S45 S61
Main hazards	alkylating agent
NFPA 704	1 3 0
Flash point	126 °C
Related compounds
Related compounds	2-chloropropionic acid sodium chloroacetate
Y acid (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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.

Production

The production of chloroacetic acid was 706,000 tonnes/year in 2010,^[2] 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 Nobel.^[2]

Processes

Chloroacetic acid is prepared industrially via two routes. The predominant method involves chlorination of acetic acid:

CH₃CO₂H + Cl₂ → ClCH₂CO₂H + HCl

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.

CCl₂CHCl + 2 H₂O → ClCH₂CO₂H + 2 HCl

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.^[3]

Reactivity and uses

Illustrative of its usefulness in organic chemistry is the O-alkylation of salicylaldehyde with chloroacetic acid, followed by decarboxylation of the resulting ether, producing benzofuran.^[4]

In industry, chloroacetic acid is used in the production of a wide variety of useful compounds, e.g., drugs, dyes, pesticides.^[3] 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.

Safety

Like other chloroacetic acids and related halocarbons, chloroacetic acid is a potentially dangerous alkylating agent. The LD₅₀ for rats is 76 mg/kg.^[3]

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).^{[citation needed]}

See also

• Chloroacetic acids
• Dichloroacetic acid
• Trichloroacetic acid
• Chloracetyl chloride

References

1. ^ Dippy, J.F.J., Hughes, S.R.C., Rozanski, A., J. Chem Soc., 1959, 2492.
2. ^ ^{a b} M.P. Malveda (july 2011). "CEH Marketing Research Report: MONOCHLOROACETIC ACID". Chemical Economics Handbook. SRI consulting. http://www.sriconsulting.com/CEH/Public/Reports/676.1000/. Retrieved July 2011. 
3. ^ ^{a b c} Günter Koenig, Elmar Lohmar, Norbert Rupprich "Chloroacetic Acids" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a06_537
4. ^ Burgstahler, A. W.; Worden, L. R. (1966). "Coumarone." Org. Synth. 46: 28.

External links

• "Monochloroacetic Acid". Dow Chemical. http://www.dow.com/webapps/lit/litorder.asp?filepath=gco/pdfs/noreg/103-00133.pdf&pdf=true. Retrieved 20 May 2007. 
• "Monochloroacetic Acid". IPCS Inchem. http://www.inchem.org/documents/pims/chemical/pim352.htm. Retrieved 20 May 2007.