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DESIGNATIONS
CAS No.: 70776-03-3
Registry name: Chlorinated naphthalenes
Chemical name: Chlorinated naphthalenes
Synonyms, Trade names; Chloronaphthalene, chloronaphthalene derivatives, PCN, Halowax
Chemical name (German): Chlorierte Naphthaline
Chemical name (French): Naphthalènes chlorés
Appearance: Except for 1-monochloronaphthalene, which is a liquid at room temperature, pure chlorinated naphthalenes are colourless, crystalline compounds
BASIC CHEMICAL AND PHYSICAL DATA
| Empirical formula: | C10H8-nCln (n=1-8) |
| Rel. molecular mass: | 162.5-404.0 g |
| Density: | 1.2 - 2.0 g/cm3 |
| Boiling point: | 250 - 440°C |
| Melting point: | -25 - 197°C |
| Flash point: | 135 - >430°C |
| Solvolysis/solubility: | soluble in aromatic solvents |
Note: |
The chemical structure of the molecules results in 75 chlorinated naphthalene congeners. The physical and chemical properties are dependent on the degree of chlorination. Whereas the melting and boiling point increase with an increase in the number of chlorine atoms, there is a simultaneous reduction in vapour pressure and water solubility. |
ORIGIN AND USE
Usage:
Chlorinated naphthalenes are used in the electrical industry and
as additives. Only isomeric mixtures characterised by their
chlorine content are commercially available.
Origin/derivation:
The substances are not found naturally. They are obtained by
batchwise chlorination of naphthalene in the presence of ferric
chloride as a catalyst.
Production figures:
Worldwide approximately 5,000 t per annum with a declining
tendency (acc. KOCH, 1989).
Toxicity
| Humans: | TCLo 30 mg/m3, inhalation (trichloronaphthalene) | acc. KOCH, 1989 |
| Mammals: | ||
| Rat: | LD50 1,540 mg/kg, oral | acc. KOCH, 1989 |
| LD50 868 mg/kg, oral (2-chloronaphthalene) | acc. KOCH, 1989 | |
| Mouse: | LD50 1,091 mg/kg, oral | acc. KOCH, 1989 |
| LD50 2,087 mg/kg, oral (2-chloronaphthalene) | acc. KOCH, 1989 | |
Characteristic effects:
Humans/mammals: Poisoning is due to oral application (foodstuffs) or inhalation. The toxicity is largely governed by the degree of chlorination. Chloracne and liver damage are especially caused by pentachloro- and hexachloronaphthalene while chlorinated naphthalenes with 1 to 3 chlorine atoms hardly have any toxic effects.
ENVIRONMENTAL BEHAVIOUR
Chlorinated naphthalenes are very resistant to degradation. Mobility is slight in water and soil, but there is a pronounced tendency towards bioaccumulation and geoaccumulation depending on the degree of chlorination. Highly chlorinated naphthalenes are very persistent. Incomplete combustion results in the formation of polychlorinated dibenzodioxins and -furans (PCDD/F).
ENVIRONMENTAL STANDARDS
Recommended limits in the USA for drinking water (acc. KOCH,
1989):
Trichloronaphthalene isomers: 3.9 m
g/l
Tetrachloronaphthalene isomers: 1.5 m
g/l
Pentachloronaphthalene isomers: 0.39 m
g/l
Hexachloronaphthalene isomers: 0.15 m
g/l
Octachloronaphthalene isomers: 0.08 m
g/l
(Refer also to 'naphthalene')
Comparison/reference values
| Medium/origin | Country | Value | Source |
| Air | up to 25 ng/m3 | acc. KOCH, 1989 | |
| Surface water | up to 200 ng/l | acc. KOCH, 1989 | |
| Seawater | up to 20 ng/l | acc. KOCH, 1989 | |
| Sediments/soil | up to 100 µg/kg | acc. KOCH, 1989 | |
| Fish | up to 0.12 µg/kg | acc. KOCH, 1989 | |
| Birds | up to 70 µg/kg | acc. KOCH, 1989 | |
| Humans (fatty tissue) | up to 15 µg/kg | acc. KOCH, 1989 |
Assessment/comments
Similarly to chlorinated biphenyls, the toxicity and the environmental persistence of chlorinated naphthalenes increase with the degree of chlorination. The use of naphthalene with a high degree of chlorination should therefore be kept to a minimum.