In organic chemistry, the chloroacetic acids (systematic name chloroethanoic acids) are three related chlorocarbon carboxylic acids:

Properties

As the number of chlorine atoms increases, the electronegativity of that end of the molecule increases, and the molecule adopts a progressively more ionic character: its density, boiling point and acidity all increase.

AcidMelting point (°C)Boiling point (°C)Density (g/cm3)pKa[1]
Acetic acid16.5118.11.054.76
Chloroacetic acid61–631891.582.87
Dichloroacetic acid9.51941.571.25
Trichloroacetic acid571961.630.77

Production

  • Chloroacetic acid is mainly made by hydrolysing trichloroethylene in the presence of sulfuric acid:
    CCl2=CHCl + 2 H2O → CH2ClCOOH + 2 HCl
  • Dichloroacetic acid is manufactured in small quantities by reducing trichloroacetic acid.
  • Trichloroacetic acid is made by directly reacting chlorine with acetic acid using a suitable catalyst.

Uses

Safety

All of these acids are unusually strong for organic acids, and should generally be treated with similar care as for strong mineral acids like hydrochloric acid. Even neutral salts however, tend to be significantly toxic, because the ions interfere in biological processes (such as the citric acid cycle) that normally process plain acetate ions. The chloroacetate anion is the most toxic, with a rat, oral LD50 of about 0.5 g/kg.

References

  1. "Ionization Constants of Heteroatom Organic Acids". Archived from the original on 2007-10-08. Retrieved 2008-02-25.
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