Vinyl chloride
From Wikipedia, the free encyclopedia
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General |
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| Name | Vinyl chloride, chloroethene |
| Chemical formula | CH2=CHCl |
| Appearance | Colorless gas |
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Physical |
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| Formula weight | 62.5 u |
| Melting point | 119 K (−154 °C) |
| Boiling point | 259 K (−13 °C) |
| Density | 0.91g/cm³ (liquid) |
| Solubility | insoluble in water |
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Thermochemistry |
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| ΔfH0gas | -28.45 kJ/mol |
| ΔfH0liquid | ? kJ/mol |
| ΔfH0solid | ? kJ/mol |
| S0gas, 1 bar | ? J/(mol·K) |
| S0liquid, 1 bar | ? J/(mol·K)] |
| S0solid | ? J/(mol·K) |
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Safety |
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| Ingestion | May cause nausea, vomiting, severe stomach pain. |
| Inhalation | Can cause dizziness, drowsiness, confusion, unconsciousness, and respiratory failure. Long-term effects such as asthma may result. |
| Skin | Frostbite and irritation can result from skin contact with the refrigerated liquid. |
| Eyes | Possible irritant. |
| More info | Hazardous Chemical Database |
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SI units were used where possible. Unless otherwise stated, standard conditions were used. |
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Vinyl chloride, also known as chloroethene in IUPAC nomenclature, is an important industrial chemical chiefly used to produce its polymer, polyvinyl chloride (PVC). At room temperature, it is a toxic, colorless gas with a sweet odor.
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[edit] History
Vinyl chloride was first produced in 1835 by Justus von Liebig and his student Henri Victor Regnault. They obtained it by treating ethylene dichloride with a solution of potassium hydroxide in ethanol.
In 1912, Fritz Klatte, a German chemist working for Griesheim-Elektron, patented a means to produce vinyl chloride from acetylene and hydrogen chloride using mercuric chloride as a catalyst. While this method was widely used during the 1930s and 1940s, it has since been superseded by more economical processes
[edit] Production
Vinyl chloride is manufactured on the industrial scale[1] from ethylene and chlorine. In the presence of iron(III) chloride as a catalyst, these compounds react to produce ethylene dichloride according to the chemical equation
- CH2=CH2 + Cl2 → ClCH2CH2Cl
Typically, this reaction is conducted in a bath of boiling ethylene dichloride. When then heated to 500 °C at 15–30 atm (1.5 to 3 MPa) pressure, the ethylene dichloride decomposes to produce vinyl chloride and hydrogen chloride.
- ClCH2CH2Cl → CH2=CHCl + HCl
In industrial practice, the hydrogen chloride produced in this step is mixed with oxygen and then reacted with additional ethylene on a copper(II) chloride catalyst to produce even more ethylene dichloride via the reaction
- CH2=CH2 + 2 HCl + ½ O2 → ClCH2CH2Cl + H2O
The hydrogen chloride consumed in this step exactly balances that produced in the second step, and the resulting balanced process neither requires hydrogen chloride as an input nor produces it as a waste. Due to the economical advantages of this process, most vinyl chloride has been produced via this technique since the late 1950s.
[edit] Uses
By far the most important use of vinyl chloride is its polymerization to make PVC. Much smaller amounts are used to produce other chlorinated hydrocarbons including ethylidene dichloride, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene, and vinylidene chloride.
Vinyl chloride's toxicity limits its use in consumer goods, though it has been historically (until 1974) utilized as an aerosol spray propellant; carcinogenic potential has long been established and the prospective legal liability is comparable to that of asbestos (implicated in the causality of mesothelioma). Accumulation of vinyl chloride vapor in hair salons readily exceeded the NOAEL (NO Adverse Effect Level) exposure guidelines, its high index of mutagenicity possibly responsible for an increase of an order of magnitude of the occurrence of cancer in the most severely affected occupations.
It was briefly used as an inhalational anaesthetic, in a similar vein to ethyl chloride, though its toxicity forced this practice to be abandoned.
[edit] Health effects
Vinyl chloride depresses the central nervous system, and inhaling its vapors produces symptoms similar to alcohol intoxication. These include headache, dizziness, and loss of coordination, and in severe cases may progress to hallucination, unconsciousness, and death by respiratory failure.
In laboratory animals, exposure to vinyl chloride during pregnancy has produced miscarriages and birth defects. Its effect on human reproduction is unknown.
Long-term exposure to vinyl chloride can cause chronic skin irritations and has also been linked to a painful inflammation of the extremities called Raynaud's syndrome. Vinyl chloride is considered to be a carcinogen and has in particular been linked to certain cancers of the liver— particularly, angiosarcoma and hepatocellular carcinoma.
