Tetrachloroethylene 127-18-4

Tetrachloroethylene 127-18-4, also known as perchloroethylene, is a compound formed by replacing all hydrogen atoms in ethylene with chlorine atoms. It was first synthesized by Faraday in 1821 during the thermal decomposition of hexachloroethane.

It is a colorless, transparent liquid with an ether-like odor. It is non-flammable. Its relative molecular mass is 165.85. Relative density: 1.6220. Melting point: -22.7°C. Boiling point: 121.2°C, 33.2°C (4.000×10³ Pa). Refractive index: 1.5055. Viscosity: 0.839 mPa·s (20°C). Vapor pressure (×10³ Pa): 5.466 (40°C), 13.865 (60°C), 30.131 (80°C), 58.128 (100°C).

Tetrachloroethylene is insoluble in sugar, glycerol, and proteins, slightly soluble in water (0.015 at 25°C), and miscible with ethanol, ether, chloroform, benzene, and chlorinated organic solvents. It does not hydrolyze.

According to Chemicalbook, it remains stable even when heated to 500°C in the absence of air, moisture, and catalysts. Hydrogenation produces tetrachloroethane. Chlorination produces hexachloroethane.

Tetrachloroethylene can also react with bromine to form monobromotrichloromethane or dibromodichloromethane compounds. Under the action of a catalyst, it can also react with hydrogen fluoride.

When exposed to light, air, and water over an extended period, it slowly decomposes into trichloroacetaldehyde and phosgene, corroding metals such as iron, aluminum, and zinc.

This decomposition can be inhibited by adding stabilizers. In the presence of activated carbon, heating to 700°C causes it to decompose into hexachlorobenzene and hexachloroethane. Tetrachloroethylene can be oxidized by strong oxidizing agents. Tetrachloroethylene reacts violently with barium powder, beryllium powder, lithium shavings, nitrogen tetroxide, and sodium hydroxide.

Tetrachloroethylene is toxic and acts as a central nervous system depressant, causing headaches, nausea, vomiting, and even coma. The oral LD50 in mice is 8850 mg/kg.

The maximum allowable concentration in the workplace is 100 × 10⁻⁶.