1,4,5,6,7,7-hexachloro-5-norbornene-2,3-dicarboxylic acid

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Structural formula
Structural formula of chlorenedioic acid
Surname 1,4,5,6,7,7-hexachloro-5-norbornene-2,3-dicarboxylic acid
other names
  • Chlorenedioic acid
  • Hexachloro-endomethylenetetrahydrophthalic acid
  • HET acid
Molecular formula C 9 H 4 Cl 6 O 4
Brief description

white solid

External identifiers / databases
CAS number 115-28-6
EC number 204-078-9
ECHA InfoCard 100.003.708
PubChem 8266
Wikidata Q1854296
Molar mass 388.84 g mol −1
Physical state


Melting point

239-242 ° C

safety instructions
GHS labeling of hazardous substances
05 - Corrosive 08 - Dangerous to health


H and P phrases H: 318-351
P: 280-305 + 351 + 338
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

1,4,5,6,7,7-hexachloro-5-norbornene-2,3-dicarboxylic acid is a chemical compound from the group of carboxylic acids and hexachloronorbornenes. The anhydride of the compound is 1,4,5,6,7,7-hexachloro-8,9,10-trinorborn-5-ene-2,3-dicarboxylic anhydride and structurally with chlorinated cyclodiene insecticides such as aldrin , dieldrin , endrin , isodrin , Endosulfan , chlordane and heptachlor related.

Extraction and presentation

1,4,5,6,7,7-hexachloro-5-norbornene-2,3-dicarboxylic acid can be obtained by a Diels-Alder reaction of hexachlorocyclopentadiene with maleic anhydride and subsequent hydrolysis of the anhydride formed.


1,4,5,6,7,7-hexachloro-5-norbornene-2,3-dicarboxylic acid is a white crystalline solid which, when heated, begins to decompose to anhydride before the melting point is reached. The compound is very resistant to hydrolytic dechlorination, easily forms salts with a wide variety of metals. It forms esters when heated with or without azeotropic solvents (e.g. chlorobenzene ) and easily forms alkyl-type polyester resins by reaction with glycols and other polyols .


1,4,5,6,7,7-Hexachloro-5-norbornene-2,3-dicarboxylic acid is used as an intermediate for the production of polyester resins and as a flame retardant .

Individual evidence

  1. a b c d e Environmental Health Criteria (EHC) for Chlorendic acid and anhydride , accessed June 20, 2018.
  2. a b c d e data sheet 1,4,5,6,7,7-Hexachloro-5-norbornene-2,3-dicarboxylic acid, 99% from Sigma-Aldrich , accessed on June 20, 2018 ( PDF ).
  3. a b c d e Entry on chlorendic acid in the Hazardous Substances Data Bank , accessed on June 12, 2018.