Trichloroacetic acid

Trichloroacetic acid
Names
Preferred IUPAC name
Trichloroacetic acid
Identifiers
3D model (JSmol)
970119
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.000.844 Edit this at Wikidata
2842
KEGG
RTECS number
  • AJ7875000
UNII
  • InChI=1S/C2HCl3O2/c3-2(4,5)1(6)7/h(H,6,7)
    Key: YNJBWRMUSHSURL-UHFFFAOYSA-N
  • ClC(Cl)(Cl)C(O)=O
Properties
C2HCl3O2
Molar mass 163.38 g·mol−1
Appearance Colorless to white, crystalline solid
Odor Sharp, pungent
Density 1.63 g/cm3
Melting point 57 to 58 °C (135 to 136 °F; 330 to 331 K)
Boiling point 196 to 197 °C (385 to 387 °F; 469 to 470 K)
1000 g/100 mL
Vapor pressure 1 mmHg (51.1 °C)
Acidity (pKa) 0.66
−73.0·10−6 cm3/mol
Structure
3.23 D
Hazards
GHS labelling:
GHS05: CorrosiveGHS09: Environmental hazard
Danger
H314, H410
P260, P264, P273, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P391, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
1
0
Lethal dose or concentration (LD, LC):
5000 mg/kg (rat, oral)
NIOSH (US health exposure limits):
PEL (Permissible)
 None
REL (Recommended)
 TWA 1 ppm (7 mg/m3)
IDLH (Immediate danger)
 N.D.
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Trichloroacetic acid (TCA; TCAA; also known as trichloroethanoic acid) is an organochlorine compound with the formula CCl3CO2H. It is an analogue of acetic acid in which the three hydrogen atoms of the methyl group have all been replaced by chlorine atoms. It is a colorless solid that dissolves in water.

Salts and esters of trichloroacetic acid are called trichloroacetates.

Synthesis and reactivity

It is prepared by the reaction of chlorine with acetic acid in the presence of a suitable catalyst such as red phosphorus.

CH3CO2H + 3 Cl2 → CCl3CO2H + 3 HCl

Another route to trichloroacetic acid is the oxidation of trichloroacetaldehyde.[citation needed]

In water, trichloroacetic acid converts to trichloroacetate as indicated by its low pKa. Thus trichloroacetic acid does not exist in aqueous solution, on the conjugate base. It can be converted to trichloroacetyl chloride using thionyl chloride.

Use

It is a precursor to various herbicides. Sodium trichloroacetate was marketed as such in the 1950s but has since been highly regulated.

Niche

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.[citation needed]

TCA and DCA are both used in cosmetic treatments (such as chemical peels and tattoo removal) 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.

Toxicity

According to the European Chemicals Agency, "This substance causes severe skin burns and eye damage, is very toxic to aquatic life and has long lasting toxic effects."

History

The discovery of trichloroacetic acid by Jean-Baptiste Dumas in 1839 delivered a striking example to the slowly evolving theory of organic radicals and valences. The theory was contrary to the beliefs of Jöns Jakob Berzelius, starting a long dispute between Dumas and Berzelius.

In the 1958 film The Blob, a bottle of trichloroacetic acid is tossed at the Blob in a futile attempt to fend it off.

See also

References

  1. 1 2 3 4 5 NIOSH Pocket Guide to Chemical Hazards #0626 National Institute for Occupational Safety and Health (NIOSH)
  2. 1 2 3 4 Budavari, Susan, ed. (1996). The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (12th ed.). Merck. ISBN 0911910123.
  3. ↑ Databog fysik kemi, F&K Forlaget 11. udgave 2009
  4. 1 2 3 4 Koenig, Günter; Lohmar, Elmar; Rupprich, Norbert (2000). "Chloroacetic Acids". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a06_537. ISBN 3-527-30673-0.
  5. ↑ TCA-sodium in the Pesticide Properties DataBase (PPDB), accessed June 20, 2014
  6. ↑ United Nations Environment Programme. "Trichloroacetic Acid CAS N°: 76-03-9" (OECD SIDS). Accessed June 20, 2014. Archived from the original on 15 August 2018.
  7. ↑ Heier, Al (December 1991). "Trichloroacetic Acid (TCA)". EPA. Accessed June 20, 2014 — via Cornell PMEP Pesticide Active Ingredient Information database. Archived from the original on 15 Aug 2020.
  8. ↑ Jones, Kirtly (June 21, 2012). Marshall, Sarah (ed.). "Trichloroacetic Acid or Bichloroacetic Acid for Genital Warts (Human Papillomavirus)". WebMD. HealthWise. Archived from the original on 16 July 2015.
  9. ↑ Wiley DJ, Douglas J, Beutner K, Cox T, Fife K, Moscicki AB, Fukumoto L (2002). "External genital warts: Diagnosis, treatment, and prevention". Clinical Infectious Diseases. 35 (Suppl 2): S210–S224. doi:10.1086/342109. PMID 12353208.
  10. ↑ "Trichloroacetic acid". C&L Inventory. European Chemical Agency. Retrieved 14 March 2022.
  11. ↑ Terchloracetic Acid in Gmelin, L., Hand-book of Chemistry: Organic chemistry
  12. ↑ Dumas (1839). "Trichloroacetic acid". Annalen der Pharmacie. 32: 101–119. doi:10.1002/jlac.18390320109.
  13. ↑ William Albert Noyes (1927). "Valence". Proceedings of the American Philosophical Society. 66: 287–308. JSTOR 3301070.