Trichloroacetic acid

Trichloroacetic acid is a strong carboxylic acid, C₂HCl₃O₂, in which three chlorine atoms replace hydrogen atoms on acetic acid’s methyl group. It is used in protein precipitation, chemical peels, and laboratory analysis.

Acid dissociation constant: A quantitative measure of an acid’s tendency to donate a proton in solution. Its low pKa accounts for trichloroacetic acid’s strong acidity.
Chemical peel: A treatment that applies a chemical solution to remove controlled layers of skin. Trichloroacetic acid is used at selected concentrations for medium-depth peels.
Acetic acid: A two-carbon carboxylic acid with formula CH₃COOH, familiar as the acid in vinegar. Replacing three methyl hydrogens in acetic acid gives trichloroacetic acid.
Hydrochloric acid: A strong inorganic acid composed of hydrogen chloride dissolved in water. Both are strong acids, but hydrochloric acid lacks trichloroacetic acid’s organic carbon framework.
Inductive effect: A shift in electron distribution transmitted through sigma bonds by electronegative atoms or charged groups. Three chlorine atoms withdraw electron density and stabilize the conjugate base.
Protein assay: A laboratory method for detecting or measuring the amount of protein in a sample. Acid precipitation can concentrate proteins or prepare samples for measurement.
Carboxylic acid: An organic compound containing a carboxyl group, –COOH. Trichloroacetic acid belongs to this family and retains its characteristic acidic group.
Perchloric acid: A strong inorganic acid with formula HClO₄. It is a much stronger mineral acid, unlike trichloroacetic acid’s moderately strong aqueous acidity.
Trichloroacetate: The conjugate base and salts of trichloroacetic acid. Deprotonation produces this ion, whose stabilization supports the acid’s strength.
Kjeldahl method: A method for measuring nitrogen in samples through digestion, distillation, and titration. Trichloroacetic acid can precipitate proteins during some nitrogen-analysis procedures.

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