Pentachlorophenol

July 19, 2021
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Pentachlorophenol is an old-line pest control agent that came under regulatory pressure decades ago. Beginning in the 1930s, it was used as an insecticide (including for termite control), a defoliant for crops before they were harvested, a wood preservative (notably in telephone poles), and a biocide with numerous other agricultural and industrial uses.

Pentachlorophenol is made by chlorinating phenol at high temperature. In the commercial process, chlorination is incomplete, and the product contains even more toxic impurities such as dibenzo-p-dioxin derivatives. The compound’s odor is similar to that of benzene or phenol; it is sparingly soluble in water and slow to decompose in nature.

Pentachlorophenol’s pervasive toxicity and environmental threats (see the hazard information table) doomed it to severe use restrictions by the 1980s. Today, wood preservation is the only use permitted by the US Environmental Protection Agency. Earlier this year, the EPA proposed to ban it completely. The comment period for this proposal expired in May, and EPA is currently proceeding with canceling the registration

For additional information, see EPA’s information page on pentachlorophenol.


Pentachlorophenol hazard information

Hazard class* GHS code and hazard statement
Acute toxicity, oral, category 3 H301—Toxic if swallowed Chemical Safety Warning
Acute toxicity, dermal, category 3 H311—Toxic  in contact with skin Chemical Safety Warning
Skin corrosion/irritation, category 2 H315—Causes skin irritation Chemical Safety Warning
Serious eye damage/eye irritation, category 2A H319—Causes serious eye irritation Chemical Safety Warning
Acute toxicity, inhalation, category 2 H330—Fatal if inhaled Chemical Safety Warning
Specific target organ toxicity, single exposure, respiratory tract irritation, category 3 H335—May cause respiratory irritation Chemical Safety Warning
Carcinogenicity, category 2 H351—Suspected of causing cancer Chemical Safety Warning
Short-term (acute) aquatic hazard, category 1 H400—Very toxic to aquatic life Chemical Safety Warning
Long-term (chronic) aquatic hazard, category 2 H411—Toxic to aquatic life with long-lasting effects Chemical Safety Warning

*Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. 
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Pentachlorophenol
fast facts

CAS Reg. No. 87-86-5
SciFinder
nomenclature
Phenol, 2,3,4,5,6-pentachloro-
Empirical formula C6HCl5O
Molar mass 266.34 g/mol
Appearance White crystals or powder
Melting point 191 °C
Water solubility 14 mg/L

MOTW update

Nitrous oxide (N2O) was the Molecule of the Week for January 14, 2013. It is the third-most-emitted climate change contributor, after carbon dioxide and methane, yet little has been done to curtail it. Now, pressure from government agencies and environmental groups is forcing the chemical industry worldwide to install equipment to abate N2O emissions.

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