Difference between revisions of "Chloroacetic acid"
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Latest revision as of 10:25, 20 September 2010
| Chloroacetic acid | |
|---|---|
| Chloroacetic acid | |
| Chloroethanoic acid | |
| style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers | |
| CAS number | 79-11-8 
|
| 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 | |
| Flash point | 126 °C |
| style="background: #F8EABA; text-align: center;" colspan="2" | Related compounds | |
| Related compounds | 2-chloropropionic acid sodium chloroacetate |
 (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
- ↑ Ionization Constants of Heteroatom Organic Acids
- ↑ 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
- ↑ Burgstahler, A. W.; Worden, L. R. (1966). "Coumarone." Org. Synth. 46: 28.
External links
- "Monochloroacetic Acid". Dow Chemical. Retrieved 20 May 2007.
- "Monochloroacetic Acid". IPCS Inchem. Retrieved 20 May 2007.cs:Kyselina chloroctová
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
