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
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	Caution
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
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

1. ↑ ^{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) .
2. ↑ ^{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) .
3. ↑ ^{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) .
4. ↑ Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values , accessed on November 2, 2015.
5. ↑ Environmental Health Criteria (EHC) for Chlorobenzenes other than Hexachlorobenzene , accessed November 19, 2014.

Web links

Commons : Trichlorobenzenes  - Collection of images, videos and audio files

• European Union Risk Assessment Report - 1,2,4-trichlorobenzene (PDF file; 4.8 MB)