Trichlorethylene

Structural formula
General
Surname	Trichlorethylene
other names	Trichlorethylene (tri) Ethylene trichloride Acetylene trichloride Triles TCE R-1120
Molecular formula	C 2 HCl 3
Brief description	colorless liquid with a sweet, ethereal odor
External identifiers / databases
CAS number 79-01-6 EC number 201-167-4 ECHA InfoCard 100.001.062 PubChem 6575 ChemSpider 13837280 DrugBank DB13323 Wikidata Q407936
properties
Molar mass	131.39 g mol −1
Physical state	liquid
density	1.46 g cm −3
Melting point	−86 ° C
boiling point	87 ° C
Vapor pressure	78 h Pa (20 ° C)
solubility	bad in water (1 g l −1 )
Refractive index	1.4782 (20 ° C)
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger H and P phrases H: 350-341-319-315-336-412 P: 201-261-273-281-305 + 351 + 338-308 + 313
Authorization procedure under REACH	of particular concern : carcinogenic ( CMR ); subject to approval
MAK	Switzerland: 20 ml m −3 or 110 mg m −3
Toxicological data	2402 mg kg −1 ( LD 50 ,  mouse ,  oral )
Thermodynamic properties
ΔH f 0	−43.6 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

Trichlorethylene (common name: trichlorethylene , trichlor , tri ) is a colorless, clear liquid. It smells like chloroform and is non-flammable. It acts as a strong solvent and was therefore used earlier in mold and roller washing agents in the printing industry and in metalworking plants as a parts cleaning agent.

Trichlorethylene dissolves polyolefins and chemically related plastics and makes them soft and opaque.

Extraction and presentation

Until the early 1970s, trichloroethene was usually produced from ethyne in a two-step process . First ethyne is reacted with chlorine , and a ferric chloride - catalyst at 90 ° C to 1,1,2,2-tetrachloroethane reacted:

${\displaystyle {\ce {HC#CH + 2Cl2 -> Cl2CHCHCl2}}}$

The 1,1,2,2-tetrachloroethane was then dehydrochlorinated to trichloroethene. This can either be done with an aqueous solution of calcium hydroxide

${\displaystyle {\ce {2Cl2CHCHCl2 + Ca(OH)2 ->2ClCH=CCl2 + CaCl2 + 2H2O}}}$

or in the gas phase by heating to 300–500 ° C with a barium or calcium chloride catalyst:

${\displaystyle {\ce {Cl2CHCHCl2 -> ClCH=CCl2 + HCl}}}$

Today trichlorethylene is mostly produced from ethene . This is first of an iron chloride catalyst by chlorination in using 1,2-dichloroethane converted

${\displaystyle {\ce {CH2=CH2 + Cl2 -> ClCH2CH2Cl}}}$

and then converted to trichlorethylene at 400 ° C with additional chlorine.

${\displaystyle {\ce {ClCH2CH2Cl + 2Cl2 -> ClCH=CCl2 + 3HCl}}}$

This reaction can be catalyzed by a large number of substances. The most common catalyst used is a mixture of potassium chloride and aluminum chloride . However, various forms of porous carbon can also be used. This reaction also produces tetrachloroethene as a by-product , which, depending on the amount of chlorine added, can also become the main product. Typically, trichloroethene and tetrachloroethene are collected and then separated by distillation.

use

Due to its good fat-dissolving properties, volatility and non-flammability, trichloroethene, in addition to related compounds such as B. tetrachlorethylene, one of the most common cleaning, degreasing and extraction agents . It was used, for example, in the metal and glass industries, in chemical cleaning and in textile processing. It is still important today as a heavy liquid for minerals and as an intermediate product in chemical syntheses . It is also used in the bitumen and asphalt industries as a solvent for bitumen.

safety instructions

Trichlorethylene is harmful and has a strong narcotic effect : Inhaling air with 200  ppm leads to fatigue. The MAK commission classified it as carcinogenic (especially kidney cancer ) (Category 1B) and germ cell mutagenic (Category 2). It is to be labeled as " toxic ".

The IARC classified trichlorethylene as a carcinogen for humans in 2014.

Air limit value at the workplace: There is currently no binding limit value in Germany. In the European Union, the Scientific Committee for Occupational Exposure Limits ( SCOEL ) recommends a limit value for workers of 10 ppm (54.7 mg / m ³ ) for 8-hour TWA and of 30 ppm (164.1 mg / m ³ ) for STEL (15 min.). In the USA the limit is 50 ppm.

Acute poisoning leads to brain damage , blindness and the loss of smell and taste .

In the body, it is converted to trichloroethene oxide , trichloroacetaldehyde , trichloroethanol and trichloroacetic acid by monooxygenases . Trichloroethanol is glucoronided and excreted with the urine, while trichloroacetic acid is concentrated and has a neurotoxic effect due to its strong binding to proteins in the blood plasma .

legislation

Existing EU legislation for the protection of employees against possible health hazards caused by chemical substances (including Chemical Agents Directive 98/24 / EC and Carcinogens Directive 2004/37 / EC) do not provide any binding minimum requirements for risk control for employees during the use phase or throughout the life cycle of trichlorethylene. However, if the ongoing discussions within the framework of the Carcinogen Directive result in the establishment of a binding maximum workplace concentration for trichlorethylene for the protection of workers, this conclusion can be checked.

The VOC Directive 1999/13 / EC and the Industrial Emissions Directive 2010/75 / EU set binding minimum requirements for the emissions of trichlorethylene to the environment, including emissions for surface cleaning. Activities with a solvent consumption below a specified threshold are not covered by these minimum requirements.

According to the European regulation, the use of trichlorethylene by persons in a concentration of more than 0.1% is prohibited. In the industry, trichlorethylene should be replaced by other products such as tetrachlorethylene ( perchlorethylene ), methylene chloride ( dichloromethane ) or other hydrocarbon derivatives ( ketones , alcohols ...) by April 21, 2016 , unless approval is applied for before October 21, 2014.

Individual evidence

1. ↑ ^{a b c d e f g h i} Entry on trichloroethene in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
2. ↑ ^{a b} Environmental Health Criteria (EHC) for trichlorethylene , accessed November 19, 2014.
3. ↑ Entry on trichlorethylene 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 .
4. ↑ Entry in the SVHC list of the European Chemicals Agency , accessed on July 14, 2014.
5. ↑ Entry in the register of substances subject to authorization of the European Chemicals Agency , accessed on July 14, 2014.
6. ↑ Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values (search for 79-01-6 or trichloroethene ), accessed on November 2, 2015.
7. ↑ Entry on trichlorethylene in the ChemIDplus database of the United States National Library of Medicine (NLM)
8. ↑ 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.
9. ↑ Lawrence Fishbein, Potential Industrial Carcinogens and Mutagens, ISBN 978-0-444-41777-0 .
10. ↑ Joachim Buddrus: Fundamentals of Organic Chemistry , Walter de Gruyter Verlag, Berlin, 4th edition, 2011, p. 252, ISBN 978-3-11-024894-4 .
11. ↑ IARC Monograph 106 - Trichlorethylene, 2014
12. ↑ Scientific Committee on Occupational Exposure Limits (SCOEL) Directorate-General for Employment, Social Affairs and Inclusion of the European Commission, accessed June 23, 2015
13. ↑ Recommendation from the Scientific Committee on Occupational Exposure Limits for Trichlorethylene. SCOEL / SUM / 142, April 2009.
14. ↑ eur-lex.europa.eu: Chemical agents directive 98/24 / EG (PDF)
15. ↑ eur-lex.europa.eu: Carcinogenic Substance Directive 2004/37 / EC (PDF)
16. ↑ eur-lex.europa.eu: VOC Directive 1999/13 / EC (PDF)
17. ↑ eur-lex.europa.eu: Industrial Emissions Directive 2010/75 / EU (PDF)
18. ↑ Regulation (EU) No. 348/2013 of the Commission of April 17, 2013 amending Annex XIV of Regulation (EC) No. 1907/2006 of the European Parliament and of the Council on the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH ) (PDF)