Chloroacetic acid

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Chloroacetic acid
Chloroacetic acid
Chloroacetic acid
Identifiers
CAS number 79-11-8 YesY
PubChem 300
ChemSpider 10772140 YesY
UNII 5GD84Y125G YesY
EC number 201-178-4
KEGG D07677 YesY
ChEBI CHEBI:27869 YesY
ChEMBL CHEMBL14090 YesY
RTECS number AF8575000
Jmol-3D images Image 1
Properties
Molecular formula C2H3ClO2
Molar mass 94.50 g mol−1
Appearance Colorless or white crystals
Density 1.58 g·cm−3, solid
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/100mL (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[1]
Refractive index (nD) 1.4351 (55 °C)
Structure
Crystal structure monoclinic
Thermochemistry
Specific
heat capacity
C
144.02 J/K mol
Std enthalpy of
formation
ΔfHo298
-490.1 kJ/mol
Hazards
MSDS External MSDS
R-phrases R25 R34 R50
S-phrases S23 S37 S45 S61
Main hazards alkylating agent
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 126 °C (259 °F; 399 K)
Autoignition temperature < 500 °C
LD50 165 mg/kg (mouse, oral)
Related compounds
Related compounds 2-chloropropionic acid
sodium chloroacetate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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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[edit]

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[edit]

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

CH
3
CO
2
H
+ Cl
2
ClCH
2
CO
2
H
+ HCl

The other main industrial route to chloroacetic acid is hydrolysis of trichloroethylene using sulfuric acid as a catalyst.

CCl
2
CHCl
+ 2 H
2
O
ClCH
2
CO
2
H
+ 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[edit]

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 take advantage of the high reactivity of the C–Cl bond. It is the precursor to the herbicide glyphosate, and 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[edit]

Like other chloroacetic acids and related halocarbons, chloroacetic acid is a hazardous 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 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).[5][6][7]

See also[edit]

References[edit]

  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. 
  2. ^ a b Malveda, M. P. (2011). "CEH Marketing Research Report: MONOCHLOROACETIC ACID". Chemical Economics Handbook. SRI consulting. Retrieved July 2011. 
  3. ^ a b c Koenig, G.; Lohmar, E.; Rupprich, N. (2005), "Chloroacetic Acids", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a06_537 
  4. ^ Burgstahler, A. W.; Worden, L. R. (1966), "Coumarone", Org. Synth. 46: 28 ; Coll. Vol. 5: 251 
  5. ^ Antidote treatment
  6. ^ Mitroka, J.G. 1989. Monochloroacetic Acid Lethality in the Rat in Relation to Lactic Acid Accumulation in the Cerebrospinal Fluid. Ph.D. Dissertation, Rutgers, State University of New Jersey, New Brunswick, NJ.;
  7. ^ Régnier JF, et al. Experimental evaluation of potential antidotes for monochloroacetic acid (MCA) acute poisoning. Hum Exp Toxicol 1996;15:850.

External links[edit]