Pentachlorobenzene

Pentachlorobenzene
IUPAC name

1,2,3,4,5-Pentachlorobenzene
Other names

PeCB
Identifiers
CAS number 608-93-5 Y
PubChem 11855
EC number 602-074-00-5
ChEMBL CHEMBL44628 N
RTECS number DA6640000
Jmol-3D images Image 1
Properties
Molecular formula C6HCl5
Molar mass 250.34 g mol−1
Appearance White or colorless crystals
Density 1.8 g/cm3[1]
Melting point

86 °C[1]
Boiling point

275-277 °C[1]
Solubility in water 0.68 mg/L[2]
Hazards
R-phrases R11 R22 R50/53
S-phrases (S2) S41 S46 S50 S60 S61
LD50 rat: 1080 mg/kg[3]
mouse: 1175 mg/kg[3]
 N (verify) (what is: Y/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Pentachlorobenzene (PeCB) is a chemical compound with the molecular formula C6HCl5 which is a chlorinated aromatic hydrocarbon. It consists of a benzene ring substituted with five chlorine atoms. PeCB was once used industrially for a variety of uses, but because of environmental concerns there are currently no large scale uses of PeCB.[4]

Contents

Production

PeCB can be produced as a byproduct of the manufacture of carbon tetrachloride and benzene. It is extracted by distillation and crystallization. The direct production of pure PeCB is not practical because of the simultaneous production of other chlorinated compounds. Since PeCB is generally produced in small quantities in the chlorination of benzene, it is also contained in other chlorobenzenes (dichlorobenzenes, trichlorobenzenes, etc.)

Today, a majority of the PeCB released into the environment is a result of backyard trash burning and municipal waste incineration.[4]

Uses

PeCB was used as an intermediate in the manufacture of pesticides, particularly the fungicide pentachloronitrobenzene.[3] Pentachloronitrobenzene is now made by the chlorination of nitrobenzene in order to avoid the use of PeCB.[4]

PeCB was a component of a mixture of chlorobenzenes added to products containing polychlorinated biphenyls in order to reduce viscosity.[4] PeCB has also been used as a fire retardant.[3]

Safety and regulation

PeCB is a persistent organic pollutant, allowing an accumulation in the food chain.[1][4] Consequently, pentachlorobenzene was added in 2009 to the list of chemical compounds covered by the Stockholm Convention, an international treaty which restricts the production and use of persistent organic pollutants.[5][6] PeCB has been banned in the European Union since 2002.

PeCB is very toxic to aquatic organisms, and decomposes on heating or on burning with the formation of toxic, corrosive fumes including hydrogen chloride.[1] Combustion of PeCB may also result in the formation of polychlorinated dibenzodioxins ("dioxins") and polychlorinated dibenzofurans.

See also

References

  1. ^ a b c d e Pentachlorobenzene Safety Card, International Programme on Chemical Safety
  2. ^ Shen, L., Wania, F., Lei, Y. D., Teixeira, C., Muir, D. C. G., Bidleman, T. F. (2005). "Compilation, evaluation, and selection of physical-chemical property data for organochlorine pesticides". J. Chem Eng. Data 50 (3): 742–768. doi:10.1021/je049693f. 
  3. ^ a b c d Pentachlorobenzene Fact Sheet, U.S. Environmental Protection Agency
  4. ^ a b c d e Pentachlorobenzene – Sources, environmental fate and risk characterization, Robert E. Bailey, EuroChlor, July 2007
  5. ^ Governments unite to step-up reduction on global DDT reliance and add nine new chemicals under international treaty, Stockholm Convention on Persistent Organic Pollutants, 9 May 2009
  6. ^ Adding the 'Nasty Nine' to the 'Dirty Dozen', thedailygreen.com