Chloroacetic acid

Chloroacetic acid
Names
	Preferred IUPAC name Chloroacetic acid
	Systematic IUPAC name Chloroethanoic acid
	Other names 2-Chloroacetic acid; 2-Chloroethanoic acid
Identifiers
CAS Number	79-11-8 ;
3D model (JSmol)	Interactive image;
3DMet	B02139;
ChEBI	CHEBI:27869 ;
ChEMBL	ChEMBL14090 ;
ChemSpider	10772140 ;
ECHA InfoCard	100.001.072
EC Number	201-178-4;
KEGG	D07677 ; C06755;
PubChem CID	300;
RTECS number	AF8575000;
UNII	5GD84Y125G ;
CompTox Dashboard (EPA)	DTXSID4020901 ;
	InChI InChI=1S/C2H3ClO2/c3-1-2(4)5/h1H2,(H,4,5) Key: FOCAUTSVDIKZOP-UHFFFAOYSA-N ; InChI=1/C2H3ClO2/c3-1-2(4)5/h1H2,(H,4,5) Key: FOCAUTSVDIKZOP-UHFFFAOYAR;
	SMILES ClCC(O)=O;
Properties
Chemical formula	ClCH2CO2H
Molar mass	94.49 g·mol−1
Appearance	Colorless or white crystals
Density	1.58 g/cm3
Melting point	63 °C (145 °F; 336 K)
Boiling point	189.3 °C (372.7 °F; 462.4 K)
Solubility in water	85.8 g/(100 mL) (25 °C)
Solubility	Soluble in methanol, acetone, diethyl ether, benzene, chloroform, ethanol
log P	0.22
Vapor pressure	0.22 hPa
Acidity (pKa)	2.86
Magnetic susceptibility (χ)	−48.1×10−6 cm3/mol
Refractive index (nD)	1.4351 (55 °C)
Structure
Crystal structure	Monoclinic
Thermochemistry
Heat capacity (C)	144.02 J/(K·mol)
Std enthalpy of; formation (ΔfH⦵298)	−490.1 kJ/mol
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	alkylating agent
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H301, H311, H314, H331, H400
Precautionary statements	P260, P261, P264, P270, P271, P273, P280, P301+P310, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P310, P311, P312, P321, P322, P330, P361, P363, P391, P403+P233, P405, P501
NFPA 704 (fire diamond)	3 1 0
Flash point	126 °C (259 °F; 399 K)
Autoignition; temperature	470 °C (878 °F; 743 K)
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	76 mg/kg.
Safety data sheet (SDS)	External MSDS
Related compounds
Related compounds	Dichloroacetic acid; Trichloroacetic acid; Fluoroacetic acid; Bromoacetic acid; Iodoacetic acid; Acetic acid; 2-Chloropropionic acid; 3-Chloropropanoic acid; 2,2-Dichloropropionic acid; Sodium chloroacetate;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Chloroacetic acid, industrially known as monochloroacetic acid (MCA), is the organochlorine compound with the formula Cl C H₂CO₂H. This carboxylic acid is a useful building block in organic synthesis. It is a colorless solid. Related compounds are dichloroacetic acid and trichloroacetic acid.

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,^[3] and in 1857 (in pure form) by the German chemist Reinhold Hoffmann (1831–1919) by refluxing glacial acetic acid in the presence of chlorine and sunlight,^[4] and then by the French chemist Charles Adolphe Wurtz by hydrolysis of chloroacetyl chloride (ClCH₂COCl), also in 1857.^[5]

Chloroacetic acid is prepared industrially by two routes. The predominant method involves chlorination of acetic acid, with acetic anhydride as a catalyst:

H₃C−COOH + Cl₂ → ClH₂C−COOH + HCl

This route suffers from the production of dichloroacetic acid and trichloroacetic acid as impurities, which are difficult to separate by distillation:

H₃C−COOH + 2 Cl₂ → Cl₂HC−COOH + 2 HCl

H₃C−COOH + 3 Cl₂ → Cl₃C−COOH + 3 HCl

The second method entails hydrolysis of trichloroethylene:

ClHC=CCl₂ + 2 H₂O → ClH₂C−COOH + 2 HCl

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.^[2]

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 and carboxymethyl starch.

Chloroacetic acid is also used in the production of phenoxy herbicides 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 and dimethoate. 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.^[2]

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.^[6]^[7]

Safety

Like other chloroacetic acids and related halocarbons, chloroacetic acid is a hazardous alkylating agent. The LD₅₀ for rats is 76 mg/kg.^[2]

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 (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.^[8]

References

^ Dippy, J. F. J.; Hughes, S. R. C.; Rozanski, A. (1959). "498. The dissociation constants of some symmetrically disubstituted succinic acids". Journal of the Chemical Society. 1959: 2492–2498. doi:10.1039/JR9590002492.
^ ^a ^b ^c ^d Koenig, G.; Lohmar, E.; Rupprich, N. (2005). "Chloroacetic Acids". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a06_537. ISBN 978-3527306732.
^ LeBlanc, Félix (1844) "Recherches sur les produits dérivés de l'éther acétique par l'action du chlore, et en particulier sur l'éther acétique perchloruré" (in French), Annales de Chimie et de Physique, 3rd series, 10 : 197–221 ; see especially p. 212.
^ Hoffmann, Reinhold (1857) "Ueber Monochloressigsäure" (in German) (On mono-chloroacetic acid), Annalen der Chemie und Pharmacie, 102 (1) : 1–20.
^ Wurtz, Adolphe (1857) "Note sur l'aldéhyde et sur le chlorure d'acétyle" (in French) (Note on aldehyde and on acetyl chloride), Annales de chimie et de physique, 3rd series, 49 : 58–62, see p. 61.
^ Burgstahler, A. W.; Worden, L. R. (1966). "Coumarone". Organic Syntheses. 46: 28. doi:10.15227/orgsyn.046.0028; Collected Volumes, vol. 5, p. 251..
^ Inglis, J. K. H. (1928). "Ethyl Cyanoacetate". Organic Syntheses. 8: 74. doi:10.15227/orgsyn.008.0074.
^ 40 C.F.R.: Appendix A to Part 355—The List of Extremely Hazardous Substances and Their Threshold Planning Quantities (PDF) (1 July 2008 ed.), Government Printing Office, archived from the original (PDF) on 25 February 2012, retrieved 29 October 2011

External links

"Monochloroacetic Acid". CABB. Archived from the original on 6 February 2015. Retrieved 6 February 2015.
"Monochloroacetic Acid". IPCS Inchem. Retrieved 20 May 2007.

[1] Dippy, J. F. J.; Hughes, S. R. C.; Rozanski, A. (1959). "498. The dissociation constants of some symmetrically disubstituted succinic acids". Journal of the Chemical Society. 1959: 2492–2498. doi:10.1039/JR9590002492.

[Ullmann-2] Koenig, G.; Lohmar, E.; Rupprich, N. (2005). "Chloroacetic Acids". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a06_537. ISBN 978-3527306732.

[3] LeBlanc, Félix (1844) "Recherches sur les produits dérivés de l'éther acétique par l'action du chlore, et en particulier sur l'éther acétique perchloruré" (in French), Annales de Chimie et de Physique, 3rd series, 10 : 197–221 ; see especially p. 212.

[4] Hoffmann, Reinhold (1857) "Ueber Monochloressigsäure" (in German) (On mono-chloroacetic acid), Annalen der Chemie und Pharmacie, 102 (1) : 1–20.

[5] Wurtz, Adolphe (1857) "Note sur l'aldéhyde et sur le chlorure d'acétyle" (in French) (Note on aldehyde and on acetyl chloride), Annales de chimie et de physique, 3rd series, 49 : 58–62, see p. 61.

[6] Burgstahler, A. W.; Worden, L. R. (1966). "Coumarone". Organic Syntheses. 46: 28. doi:10.15227/orgsyn.046.0028; Collected Volumes, vol. 5, p. 251..

[7] Inglis, J. K. H. (1928). "Ethyl Cyanoacetate". Organic Syntheses. 8: 74. doi:10.15227/orgsyn.008.0074.

[gov-right-know-8] 40 C.F.R.: Appendix A to Part 355—The List of Extremely Hazardous Substances and Their Threshold Planning Quantities (PDF) (1 July 2008 ed.), Government Printing Office, archived from the original (PDF) on 25 February 2012, retrieved 29 October 2011

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]