Tetrachlorobenzenes

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Tetrachlorobenzenes
Surname 1,2,3,4-tetrachlorobenzene 1,2,3,5-tetrachlorobenzene 1,2,4,5-tetrachlorobenzene
other names 1,2,3,4-tetrachlorobenzene
1,2,3,4-TeCB
1,2,3,5-tetrachlorobenzene
1,2,3,5-TeCB
1,2,4,5-tetrachlorobenzene
1,2,4,5-TeCB
Structural formula Structure of 1,2,3,4-tetrachlorobenzene Structure of 1,2,3,5-tetrachlorobenzene Structure of 1,2,4,5-tetrachlorobenzene
CAS number 634-66-2 634-90-2 95-94-3
PubChem 12463 12468 7270
Molecular formula C 6 H 2 Cl 4
Molar mass 215.89 g mol −1
Physical state firmly
Brief description colorless crystals with a
characteristic odor
gray odorless
powder
gray odorless
powder
Melting point 47 ° C 51 ° C 139-142 ° C
boiling point 246 ° C 246 ° C 240-246 ° C
density 1.73 g cm −3 (20 ° C) - 1.86 g cm −3 (22 ° C)
solubility 28 mg l −1 (25 ° C) very poorly soluble 0.3 mg l −1 (22 ° C)
practically insoluble in water, soluble in organic solvents
GHS
labeling
07 - Warning 09 - Dangerous for the environment
Caution
H and P phrases 302-410
no EUH phrases
273 273-501 273

The tetrachlorobenzenes form a group of organochlorine compounds consisting of a benzene ring with four chlorine atoms  (–Cl) as substituents . Their different arrangement results in three constitutional isomers with the empirical formula C 6 H 2 Cl 4 .

Extraction and presentation

Tetrachlorobenzenes are obtained by catalytic chlorination of trichlorobenzenes (e.g. with iron (III) chloride as a catalyst ).

They are also obtained as an intermediate synthesis product in the manufacture of chlorobenzenes. If the amount of chlorinating agent used is significantly increased during production, larger amounts of dichlorobenzenes can be obtained, with chlorobenzene and the more highly chlorinated benzenes such as tetrachlorobenzenes 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. 1,2,4,5-tetrachlorobenzene, which has the highest symmetry, has the highest melting point. The tetrachlorobenzenes are practically insoluble in water, but soluble in organic solvents.

use

1,2,3,5- and especially 1,2,4,5-tetrachlorobenzene are used as an intermediate product in the manufacture of herbicides , insecticides , defoliants and other chemical compounds such as 2,4,5-trichlorophenol (which, for example, in the Sevesounglück der Case was) used.

Reaction sequence

In addition, they are used as waterproofing agents in electrical insulation and as temporary protection in seals.

1,2,3,4-Tetrachlorobenzene serves as an intermediate product (as a mixture with the 1,2,4,5-isomer) for pentachloronitrobenzene and as a component of dielectric liquids.

safety instructions

Polychlorinated biphenyls can be formed from tetrachlorobenzenes through exposure to sunlight . When heated, the substances decompose, whereby the formation of hydrogen chloride , carbon monoxide , carbon dioxide , chlorine , phosgene , polychlorodibenzo-p-dioxins and polychlorodibenzofurans is possible. The acute oral LD 50 value is around 1500 mg / kg.

Individual evidence

  1. a b c d e f Entry on 1,2,3,4-tetrachlorobenzene in the GESTIS substance database of the IFA , accessed on October 14, 2012(JavaScript required) .
  2. a b c d e f Entry on 1,2,3,5-tetrachlorobenzene in the GESTIS substance database of the IFA , accessed on October 14, 2012(JavaScript required) .
  3. a b c d e f Entry on 1,2,4,5-tetrachlorobenzene in the GESTIS substance database of the IFA , accessed on October 14, 2012(JavaScript required) .
  4. Process for 1,2,4,5-Tetrachlorobenzene (Freepatentsonline)
  5. Tetrachlorobenzene (EPA) (PDF file; 8 kB)
  6. 1,2,4,5-tetrachlorobenzene (Enius)
  7. 1,2,3,5-tetrachlorobenzene (Enius)
  8. 1,2,3,4-tetrachlorobenzene (Enius)
  9. Toxicity to laboratory animals (VetPharm)

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