CAS number
- 608-93-5
Molecular formula
- C6HCl5
Formula weight
- 250.3 g/mol
Family
- Chlorobenzenes
Compound properties list|
| Melting/boiling point | 85 °C | Solid |
| Relative density | 1.83 g/cm3 | Sinks in water |
| Vapour pressure | 0.006 mm Hg | Very low volatility |
| Vapour density | 0 | N/A |
| Solubility in water | 0.5 mg/L | Very low solubility |
| Henry's law constant | 6 x 10-4atm·m3/mol | Moderately volatile when dissolved |
| log Koc (Depending on soil or sediment characteristics) | 4.1 - 6.3* | Very strong adsorption to organic matter |
At 20 0C, pentachlorobenzene is a solid with very low volatility and solubility. Once it is
dissolved, it is moderately volatile and adsorbs very strongly to organic matter. When present in
the soil, it volatilizes and dissolves very slowly. In the dissolved phase, pentachlorobenzene can
reach the water table or drain into a waterway where it will be diluted before partially
volatilizing. Fragments of pentachlorobenzene can also be carried into waterways where they will be
deposited at the bottom and dissolve very slowly. Once the source has been removed, the adsorbed
phase will take a very long time to disappear, liberating contamination in either the gaseous or
dissolved state. The resulting plumes (gaseous and dissolved) are generally small in size.
In Canada, pentachlorobenzene is considered "toxic", as defined under Paragraph 64(a) of
CEPA 1999, and has been added to Schedule 1.
Pentachlorobenzene is not currently produced or used in its pure form in Canada. The
principal current commercial use of pentachlorobenzene is as a chemical intermediate in the
formation of pentachloronitrobenzene (also known as quintozene), a fungicide which is currently
used, but not produced, in Canada. Pentachlorobenzene is present as an impurity in this and other
herbicides, pesticides and fungicides currently in use in Canada. Pentachlorobenzene is also present
as an impurity in pentachlorophenol, one of the five main wood treatment chemicals that are used in
Canada.
Pentachlorobenzene may be present as an undesirable by-product in the manufacture of
hexachlorobenzene, pentachloronitrobenzene, tetrachlorobenzenes, tetrachloroethylene,
trichloroethylene, and 1,2-dichloroethane.
Pentachlorobenzene was a component of a mixture of chlorobenzenes added to products containing
polychlorinated biphenyls (transformer dielectric fluids) in order to reduce viscosity. In Canada,
approximately 200,000 kg of pentachlorobenzene are present in transformer dielectric fluids either
in use or stored before disposal. Pentachlorobenzene has also been used as a fire retardant.
Canadian Council of Ministers of the Environment. 1999. Canadian water quality
guidelines for the protection of aquatic life: Chlorinated benzenes-Pentachlorobenzene. In:
Canadian environmental quality guidelines, 1999. Canadian Council of Ministers of the Environment,
Winnipeg. Canada. (Viewed December 2013)
Environment Canada. 2009. CEPA Environmental Registry: Toxic Substances List-Updated Schedule
1 as of December 27, 2006. (Viewed December 2013)
Environment Canada. 2009. Management of Toxic Substances: Pentachlorobenzenes (QCB). (Viewed December 2013)
Montgomery, John H. 2007. Groundwater Chemicals, Desk Reference, Fourth Edition, CRC
Press, Taylor and Francis Group, Florida, U.S.A.
