Vinyl chloride

March 06, 2023
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Vinyl chloride is a colorless gas with a mild, sweet odor that belies how hazardous it is. (See the hazard information table.) It has been in the news lately because of the February 3 rail disaster in East Palestine, OH.

Vinyl chloride has been known since at least 1835, when Henri Victor Regnault at the University of Giessen (Germany)1 synthesized it via the reaction of 1,2-dichloroethane2 and potassium hydroxide in ethanol solution. 1,2-Dichloroethane, frequently called ethylene dichloride, is still the precursor to vinyl chloride today. In 2021, the worldwide market for vinyl chloride was 51 megatonnes.

By far the largest use of vinyl chloride is in the manufacture of poly(vinyl chloride)3 (PVC) plastics, which have a multitude of applications that range from pipes to packaging to phonograph records (“vinyls”). Until the 1970s, vinyl chloride was also a commercial refrigerant; its use was discontinued because of its virulent toxicity.

The train derailment in East Palestine included five railcars that carried almost 500,000 L of vinyl chloride as a liquefied gas. Only one of the cars released a small amount of its contents; but the authorities, fearing a vinyl chloride explosion caused by fires from other derailed cars, decided to conduct a controlled release and burn of the chemical in all five cars. This operation resulted not only in the release of highly toxic vinyl chloride but also in the formation of extremely hazardous combustion products, particularly the gases hydrogen chloride4 and phosgene5.

For other compounds released by the derailment, see the sidebar “Additional East Palestine chemical releases”. In the weeks after the accident, the handling of its effects on the residents was widely criticized, as reported in C&EN on February 17.

The authorities state that the cleanup is mostly complete; but air, soil, and water testing will continue indefinitely. Although the US Environmental Protection Agency states that the air quality is normal, residents continue to experience symptoms such as headaches and rashes. The release will likely cause long-term environmental damage.

EPA issues a daily update on its response to the derailment.

1. Regnault was a student of the renowned chemist Justus von Liebig, for whom the university is now named.
2. CA Reg. No. 107-06-2.
3. CA Reg. No. 9002-86-2.
4. CA Reg. No. 7647-01-0.
5. CA Reg. No. 75-44-5.

Vinyl chloride hazard information*

Hazard class** GHS code and hazard statement
Flammable gases, category 1 H220—Extremely flammable gas; may form explosive mixtures with air Chemical Safety Warning
Gases under pressure, liquefied gas H280—Contains gas under pressure; may explode if heated Chemical Safety Warning
Acute toxicity, dermal, category 2 H310—Fatal in contact with skin Chemical Safety Warning
Serious eye damage/eye irritation, category 2B H320—Causes eye irritation Chemical Safety Warning
Specific target organ toxicity, single exposure, respiratory tract irritation, category 3 H335—May cause respiratory irritation Chemical Safety Warning
Specific target organ toxicity, single exposure, narcotic effects, category 3 H336—May cause drowsiness or dizziness Chemical Safety Warning
Germ cell mutagenicity, category 2 H341—Suspected of causing genetic defects Chemical Safety Warning
Carcinogenicity, category 1A H350—May cause cancer Chemical Safety Warning
Reproduction toxicity, category 2 H361—Suspected of damaging fertility or the unborn child Chemical Safety Warning
Specific target organ toxicity, repeated exposure, category 1 H372—Causes damage to liver, blood, nervous system, lymphatic system, musculoskeletal system, respiratory system, through prolonged or repeated exposure Chemical Safety Warning
Simple asphyxiant*** May displace oxygen and cause rapid suffocation

*Compilation of multiple safety data sheets.
**Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. Explanation of pictograms.
*** Hazard class not included in GHS; no pictogram assigned.

Additional East Palestine chemical releases

Vinyl acetate was the most hazardous chemical released in East Palestine, but the five other compounds that were released pose various degrees of danger as well. Two are solvents and the other three are monomers. The table lists the chemicals and their hazardous properties.

Compound            CA Reg. No. Amount released (L) Primary
Primary hazardous
Benzene 71-43-2 228,000 Solvent Carcinogen
2-Butoxyethanolb 111-76-2 114,000 Solvent, surfactant Skin, eye
damage / irritation
Isobutylene 115-11-7 114,000 Monomer, feedstock Gas under pressure, asphyxiant
n-Butyl acrylate 141-32-2 114,000 Monomer Skin, eye irritation / sensitization
2-Ethylhexyl acrylate 103-11-7 98,000 Monomer Skin irritation / sensitization, reproductive toxicity

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Vinyl chloride fast facts

CAS Reg. No. 75-01-4
SciFinder nomenclature Ethene, chloro-
Empirical formula C2H3Cl
Molar mass 62.50 g/mol 
Appearance Colorless gas
Boiling point –13 °C
Water solubility ≈1.0 g/L (15–85 °C)
Chemical Abstract Service - a division of ACS

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