Trichlorobenzenes
Trichlorobenzenes | |||||
Surname | 1,2,3-trichlorobenzene | 1,2,4-trichlorobenzene | 1,3,5-trichlorobenzene | ||
other names | 1,2,3-TCB | 1,2,4-TCB | 1,3,5-TCB | ||
Structural formula | |||||
CAS number | 87-61-6 | 120-82-1 | 108-70-3 | ||
12002-48-1 (mixture of isomers) | |||||
PubChem | 6895 | 13 | 7950 | ||
Molecular formula | C 6 H 3 Cl 3 | ||||
Molar mass | 181.45 g mol −1 | ||||
Physical state | firmly | liquid | firmly | ||
Brief description | white crystals with a faint aromatic odor |
colorless liquid with an aromatic odor |
colorless to white crystals with a smell of mothballs |
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Melting point | 53 ° C | 17 ° C | 63 ° C | ||
boiling point | 211 ° C | 213 ° C | 209 ° C | ||
density | 1.69 g cm −3 | 1.46 g cm −3 (20 ° C) | 1.87 g cm −3 (64 ° C) | ||
solubility | 16 mg l −1 (20 ° C) | 35 mg l −1 (25 ° C) | 4.1–5.9 mg l −1 (20 ° C) | ||
practically insoluble in water, soluble in organic solvents | |||||
GHS labeling |
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H and P phrases | 302-410 | 302-315-410 | 302-411 | ||
no EUH phrases | no EUH phrases | no EUH phrases | |||
262-273 | 273-302 + 352 |
264-270-273 301 + 312-330-501 |
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MAK | Switzerland: 5 ml m −3 or 38 mg m −3 |
In chemistry, trichlorobenzenes form a group of substances consisting of a benzene ring with three chlorine atoms (–Cl) as substituents . Their different arrangement results in three constitutional isomers with the empirical formula C 6 H 3 Cl 3 .
Extraction and presentation
Trichlorobenzenes are obtained by the catalytic chlorination of dichlorobenzenes .
They occur in large quantities as a synthesis intermediate. If benzene is used directly with chlorine in the presence of a Lewis acid , such as. B. iron (III) chloride or aluminum chloride reacted, the main product obtained is chlorobenzene in 80-90% yield. In this reaction, trichlorobenzenes are only obtained in small amounts as by-products. However, if the amount of chlorinating agent used is increased significantly, larger amounts of dichlorobenzenes can be obtained, with chlorobenzene and the more highly chlorinated benzenes such as trichlorobenzenes still being formed as by-products.
properties
The boiling points of the three isomers are relatively close to one another, while their melting points differ more clearly. The 1,3,5-trichlorobenzene, which has the highest symmetry, has the highest melting point. The trichlorobenzenes are practically insoluble in water and soluble in organic solvents.
use
Trichlorobenzenes are increasingly used as starting materials and intermediates for pharmaceuticals, pesticides, dyes and pesticides. They serve as solvents for paints, rubber, waxes, resins and disinfectants.
1,2,3-Trichlorobenzene is used as a herbicide .
1,2,4-Trichlorobenzene is used as a heat transfer agent, termite poison, solvent in the processing of polyester fibers, an additive in oils and lubricants and as an intermediate in the manufacture of herbicides. The earlier use as a dielectric in transformers was stopped because of the formation of highly toxic polychlorinated dioxins and dibenzofurans .
1,3,5-Trichlorobenzene is used as a termite control agent and coolant. It is also found in electrical insulators and transformer oil.
safety instructions
The MAK commission has set a value of 5 ml / m 3 and 38 mg / m 3 for 1,2,3- and 1,3,5-trichlorobenzene . 1,2,4-Trichlorobenzene is classified as a category 3B carcinogen (substances which give cause for concern because of their proven / possible carcinogenic effects). The vapors of 1,3,5-trichlorobenzene can form an explosive mixture with air when the substance is heated above its flash point. 1,2,3- and 1,2,4-trichlorobenzene are very toxic to aquatic organisms.
The substances generally decompose in the heat, releasing phosgene and hydrogen chloride .
Individual evidence
- ↑ a b c d e f g Entry on 1,2,3-trichlorobenzene in the GESTIS substance database of the IFA , accessed on March 25, 2017(JavaScript required) .
- ↑ a b c d e f g Entry on 1,2,4-trichlorobenzene in the GESTIS substance database of the IFA , accessed on March 25, 2017(JavaScript required) .
- ↑ a b c d e f g Entry on 1,3,5-trichlorobenzene in the GESTIS substance database of the IFA , accessed on March 25, 2017(JavaScript required) .
- ↑ Swiss Accident Insurance Fund (Suva): Limit values - current MAK and BAT values , accessed on November 2, 2015.
- ↑ Environmental Health Criteria (EHC) for Chlorobenzenes other than Hexachlorobenzene , accessed November 19, 2014.
Web links
- European Union Risk Assessment Report - 1,2,4-trichlorobenzene (PDF file; 4.8 MB)