PCE

PCE
Name	Perchloroethylene
Othernames	Tetrachloroethylene; Perc; Perc solvent
Cas number	127-18-4
Formula	C2Cl4
Molar mass	165.83 g·mol−1
Density	1.622 g·cm−3 (20 °C)
Boiling point	121 °C
Melting point	−22 °C
Solubility	150 mg·L−1 (20 °C)

PCE PCE is a chlorinated hydrocarbon widely used as an industrial solvent and chemical intermediate. It is a nonflammable, volatile, colourless liquid with a sweet, ether-like odor, employed historically in textile, metal, and building-service sectors and commonly associated with dry cleaning operations, aeronautical industry maintenance, and pharmaceutical synthesis. PCE’s physical properties and persistence have made it the subject of environmental, occupational, and regulatory attention involving agencies such as the United States Environmental Protection Agency and international bodies.

Definition and Nomenclature

The preferred IUPAC name for PCE is tetrachloroethylene, often abbreviated in industry as "perc" or "PCE". Synonyms and registry identifiers include the Chemical Abstracts Service number 127-18-4 and entries in the PubChem and ChemSpider databases. Trade names and brand labels historically tied to textile and solvent manufacturers include proprietary designations marketed by firms such as E. I. du Pont de Nemours and Company, Dow Chemical Company, and BASF SE, which appear in safety data sheets and regulatory filings. The substance is listed under classifications used by the Organisation for Economic Co-operation and Development and the International Agency for Research on Cancer.

Chemical Properties and Synthesis

Chemically, PCE is a fully chlorinated two‑carbon alkene derivative (C2Cl4) with structural analogy to ethylene where all hydrogen atoms are substituted by chlorine. It is produced industrially by chlorination and dehydrochlorination routes starting from precursors such as 1,2-dichloroethane or the chlorination of propylene followed by dehydrohalogenation and dechlorination steps. Commercial processes historically involved catalytic chlorination using agents developed by firms like Union Carbide and heat‑driven elimination stages similar to those in the manufacture of trichloroethylene. PCE exhibits low polarity, low miscibility with water, high volatility and a high density relative to water, which affects phase behavior in soil and groundwater and its compatibility with plastics and elastomers specified by manufacturers such as DuPont and 3M.

Uses and Industrial Applications

PCE’s principal historic use was as a solvent in the dry cleaning industry and for textile and leather processing, often replacing flammable solvents such as gasoline derivatives. It has been used as a degreaser in metalworking and precision cleaning in the aerospace industry for components used by organizations like Boeing and Airbus, and in formulations within pharmaceutical intermediate production and resin processing. PCE has applications as an intermediate in chemical synthesis for chlorinated intermediates utilized by specialty chemical firms, and it has served in spot-cleaning products distributed by retailers such as Procter & Gamble and professional service suppliers. Occupational applications connected to firms and unions including United Steelworkers and trade associations have driven training and solvent substitution programs.

Environmental Fate and Toxicology

In environmental systems, PCE is persistent and classified among dense non-aqueous phase liquids (DNAPLs), leading to subsurface pooling and long-term groundwater plumes documented in contamination cases investigated by agencies like the United States Geological Survey and Environment Canada. PCE undergoes anaerobic reductive dechlorination under certain microbial communities, transforming via intermediates such as trichloroethylene and dichloroethylene to vinyl chloride in localized aquifers studied in remediation projects by groups including the National Aeronautics and Space Administration and university research centers. Toxicologically, acute inhalation exposure can produce central nervous system depression described in clinical literature from institutions such as Mayo Clinic and Johns Hopkins Hospital, while chronic exposure has been evaluated for neurotoxicity, hepatotoxicity, and potential carcinogenicity by the International Agency for Research on Cancer, which has classified related chlorinated solvents in assessments influencing occupational limits set by Occupational Safety and Health Administration and National Institute for Occupational Safety and Health.

Regulation and Risk Management

Regulatory frameworks addressing PCE include ambient water and drinking water guidance from the United States Environmental Protection Agency and contaminant strategies under national environmental acts in jurisdictions such as United Kingdom administrations and the European Chemicals Agency. Occupational exposure limits have been promulgated by bodies like OSHA and ACGIH, which issue threshold limit values and biological exposure indices used by industrial hygienists in companies including General Electric and Siemens. Remediation standards and risk assessment methodologies employed by consulting firms and governmental sites reference protocols from the Environmental Protection Agency Superfund program and international guidance from the World Health Organization. Risk management measures include substitution with alternative solvents promoted by cleaner production initiatives championed by organizations such as the United Nations Environment Programme.

Historical Context and Incidents

PCE rose to prominence in the 20th century as industrial chemistry expanded, with major manufacturers like Monsanto and Union Carbide producing large volumes for the textile and metalworking sectors. Notable contamination and litigation cases, including municipal water supply incidents and Superfund sites, have involved municipalities, corporations, and legal entities comparable to cases seen with Benzene and Trichloroethylene contamination. High‑profile occupational exposure investigations and toxic tort claims have appeared in courts paralleling litigation histories involving Asbestos and other industrial chemicals, prompting changes in workplace practice, regulatory scrutiny, and community remediation efforts led by agencies such as the Environmental Protection Agency and State environmental agencies.

Category:Chlorinated solvents