Trichloroacetic acid
Trichloroacetic acid is an analogue of acetic acid in which the three hydrogen atoms of the methyl group have all been replaced by chlorine atoms. Salts and esters of trichloroacetic acid are called trichloroacetates.
Synthesis
Trichloroacetic acid was discovered by Jean-Baptiste Dumas in 1830.It is prepared by the reaction of chlorine with acetic acid in the presence of a suitable catalyst such as red phosphorus. This reaction is Hell–Volhard–Zelinsky halogenation.
Another route to trichloroacetic acid is the oxidation of trichloroacetaldehyde.
Use
Trichloroacetic acid is widely used in biochemistry for the precipitation of macromolecules, such as proteins, DNA, and RNA. TCA is used during oligonucleotide synthesis during the "deblocking" step to remove the dimethoxytrityl protecting group from the growing DNA/RNA strand for the next nucleotide incorporation. TCA and DCA are both used in cosmetic treatments and as topical medication for chemoablation of warts, including genital warts. It can kill normal cells as well. It is considered safe for use for this purpose during pregnancy.The sodium salt was used as an herbicide starting in the 1950s but regulators removed it from the market in the late 1980s and early 1990s.