Trichloroacetic acid

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Structural formula
Structural formula of trichloroacetic acid
Wedges to clarify the geometry
General
Surname Trichloroacetic acid
other names
  • Trichloroethanoic acid
  • 2,2,2-trichloroethanoic acid
  • TCA
Molecular formula C 2 HCl 3 O 2
Brief description

colorless, slightly acidic smelling crystals

External identifiers / databases
CAS number 76-03-9
EC number 200-927-2
ECHA InfoCard 100,000,844
PubChem 6421
ChemSpider 10772050
Wikidata Q410116
properties
Molar mass 163.39 g mol −1
Physical state

firmly

density

1.61 g cm −3 (64 ° C)

Melting point

59 ° C

boiling point

196 ° C

Vapor pressure

0.1 h Pa (20 ° C)

pK s value

0.65

solubility

very easily in water (1300 g l −1 at 20 ° C), ethanol and diethyl ether

Refractive index

1.4603 (61 ° C)

safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary
05 - Corrosive 09 - Dangerous for the environment

danger

H and P phrases H: 314-410
P: 273-280-303 + 361 + 353-304 + 340-310-305 + 351 + 338-391
MAK

Switzerland: 1 ml m −3 or 7 mg m −3

Toxicological data
Thermodynamic properties
ΔH f 0

−503.3 kJ / mol

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

The trichloroacetic acid (short TCA , from the English trichloroacetic acid ) is a chlorinated organic chemical compound from the group of carboxylic acids . The three hydrogen atoms of the methyl group are completely replaced ( substituted ) by chlorine atoms . Their salts are called trichloroacetates .

properties

Trichloroacetic acid, Cl 3 CCOOH, is provided with a pK s value of 0.65 because of the -I effect a much stronger acid than acetic acid (pK s 4.75). It forms colorless, pungent-smelling crystals with a melting point of 59 ° C and a boiling point of 196 ° C. Trichloroacetic acid is also very hygroscopic .

use

Trichloroacetic acid is used in cosmetics to remove calluses (" peeling "). However, trichloroacetic acid is banned as an ingredient in cosmetic products in Europe. Its sodium salt, sodium trichloroacetate , was used as a herbicide . There is no longer any approval as a plant protection product in the European Union or Switzerland.

In medicine, TCA is a treatment option for genital warts . For this purpose, an 80–90% solution is applied to the warts and the excess acid is then neutralized with baking soda .

Around 40% trichloroacetic acid is also used to either stop insatiable nosebleeds by etching the corresponding blood vessel, or to preventively prevent sensitive vessels of the nasal mucous membrane from tearing open.

In addition, it is used in the course of a TCA precipitation as a precipitant for proteins from a cell homogenate or from the culture medium (in the case of extracellular proteins).

In analytical chemistry, easily soluble metals can be extracted from complex biological samples such as food or body juices with trichloroacetic acid, so that there is no need for complicated, wet-chemical oxidation of the disruptive organic matrix. For example, if the calcium content of milk or the iron content in blood is to be determined, the aqueous sample material is mixed with a TCA solution in a ratio of 1: 1 and centrifuged after a short extraction time. The sediment contains insoluble components such as denatured proteins and cell fragments. The protruding solution can be measured directly.

safety instructions

The IARC classified trichloroacetic acid as a possible carcinogen in 2014.

See also

Individual evidence

  1. ↑ a b c d e f g Entry on trichloroacetic acid in the GESTIS substance database of the IFA , accessed on February 22, 2017(JavaScript required) .
  2. ↑ a b c d Entry on trichloroacetic acid. In: Römpp Online . Georg Thieme Verlag, accessed on October 14, 2014.
  3. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-490.
  4. ↑ Entry on trichloroacetic acid in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
  5. ↑ Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values (search for 76-03-9 or trichloroacetic acid ), accessed on November 2, 2015.
  6. ↑ Drugs in Japan Vol. 6 , Pg. 879, 1982.
  7. ↑ a b Entry on trichloroacetic acid in the ChemIDplus database of the United States National Library of Medicine (NLM), accessed on October 24, 2017.
  8. ^ Summary Tables of Biological Tests , National Research Council Chemical-Biological Coordination Center. Vol. 6, Pg. 214, 1954.
  9. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-21.
  10. ↑ Annex II of Regulation (EC) No. 1223/2009 .
  11. ↑ General Directorate Health and Food Safety of the European Commission: Entry on TCA in the EU pesticide database; Entry in the national registers of plant protection products in Switzerland , Austria and Germany ; accessed on February 17, 2016.
  12. ↑ GUIDELINES FOR THE MANAGEMENT OF SEXUALLY TRANSMITTED INFECTIONS WHO 2003, page 52, accessed on June 8, 2014 (PDF; 2.82 MB).
  13. ↑ Article Nosebleed (epistaxis): Therapy on Onmeda.de, accessed on March 2, 2015.
  14. ↑ IARC Monograph 106 - Trichloroacetic Acid, 2014

Web links

Wiktionary: Trichloroacetic acid  - explanations of meanings, word origins, synonyms, translations