Chloroacetic acid

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Chloroacetic acid
Names
IUPAC name
Chloroethanoic acid
Preferred IUPAC name
Chloroethanoic acid
Systematic IUPAC name
Chloroethanoic acid
Other names
2-Chloroacetic acid
α-Chloroacetic acid
Properties
C2H3ClO2
Molar mass 94.49 g/mol
Appearance Colorless or white crystals
Odor Vinegar-like
Density 1.58 g/cm3
Melting point 63 °C (145 °F; 336 K)
Boiling point 189.3 °C (372.7 °F; 462.4 K)
85.8 g/100ml (25 °C)
Solubility Soluble in acetone, benzene, chloroform, diethyl ether, ethanol, methanol
Slightly soluble in carbon tetrachloride, hexane
Vapor pressure 6.50·10-2 mmHg at 25 °C
Acidity (pKa) 2.86
Thermochemistry
-490.1 kJ/mol
Hazards
Safety data sheet Sigma-Aldrich
Flash point 126 °C (259 °F; 399 K)
Lethal dose or concentration (LD, LC):
165 mg/kg (mouse, oral)
Related compounds
Related compounds
Acetic acid
Fluoroacetic acid
Bromoacetic acid
Iodoacetic acid
Dichloroacetic acid
Trichloroacetic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Chloroacetic acid or monochloroacetic acid (MCA), is an organochlorine compound with the formula ClCH2CO2H.

Properties

Chemical

Hydrolysis of chloroacetic acid will yield glycolic acid.

ClCH2COOH + 2 NaOH → OH-CH2COONa + NaCl + H2O

Physical

Chloroacetic acid is a colorless solid, very soluble in water.

Availability

Chloroacetic acid is very difficult to acquire, as it's very toxic. It's salts however, are much more accessible and safer to handle.

Preparation

Chloroacetic acid is prepared industrially via two routes.

The predominant method involves chlorination of acetic acid, with acetic anhydride as a catalyst, in the presence of UV light. Sulfur can also be used as catalyst[1], as can red phosphorus[2].

CH3COOH + Cl2 → ClCH2COOH + HCl

This reaction also produces acetyl chloride as side product, which may be recovered.

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

CCl2=CHCl + 2 H2O → ClCH2COOH + 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.

Projects

Handling

Safety

Chloroacetic acid is toxic by inhalation, ingestion and skin contact. It is corrosive to metals and tissue. Wear gloves when handling the compound, and make sure you do not breathe the fumes.

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.

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).

Storage

Chloroacetic acid should be kept in closed bottles with a proper label.

Disposal

Chlorocetic acid can be neutralized with an excess of sodium hydroxide to sodium glycolate, which can be poured down the drain.

References

  1. http://www.prepchem.com/synthesis-of-chloroacetic-acid/
  2. https://www.erowid.org/archive/rhodium/chemistry/chloroacetic.html

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