Difference between revisions of "Chloroacetic acid"

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Chloroacetic acid
style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers
CAS number 79-11-8 YesY
RTECS number AF8575000
style="background: #F8EABA; text-align: center;" colspan="2" | Properties
Molecular formula C2H3ClO2
Molar mass 94.50 g mol−1
Appearance Colourless or white crystals
Density 1.58 g cm−3, solid
Melting point

63 °C

Boiling point

189 °C

Solubility in water Soluble
Acidity (pKa) 2.87[1]
style="background: #F8EABA; text-align: center;" colspan="2" | Hazards
MSDS External MSDS
R-phrases 25-34-50
S-phrases 23-37-45-61
NFPA 704
1
3
0
Flash point 126 °C
style="background: #F8EABA; text-align: center;" colspan="2" | Related compounds
Related compounds 2-chloropropionic acid
sodium chloroacetate
 YesY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Chloroacetic acid is the organochlorine compound with the formula ClCH2CO2H. This carboxylic acid is a useful building block in organic synthesis.

Production

Chloroacetic acid is prepared industrially via two routes. The predominant method involve 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 + 2HCl

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.[2]

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, produces benzofuran.[3]

Industrially, chloroacetic acid is used in the production of a wide variety of useful compounds, e.g. drugs, dyes, pesticides.[2] 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 76mg/kg.[2]

See also

References

  1. Ionization Constants of Heteroatom Organic Acids
  2. 2.0 2.1 2.2 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
  3. Burgstahler, A. W.; Worden, L. R. (1966). "Coumarone." Org. Synth. 46: 28.

External links

de:Chloressigsäure fr:Acide chloroacétique nl:Chloorazijnzuur ja:クロロ酢酸 pt:Ácido cloroacético ru:Монохлоруксусная кислота fi:Kloorietikkahappo sv:Klorättiksyra zh:一氯乙酸