1,2-Dichloroethane

The chemical compound 1,2-dichloroethane, commonly known by its old name of ethylene dichloride (EDC), is a chlorinated hydrocarbon, mainly used to produce vinyl chloride monomer (VCM, chloroethene), the major precursor for PVC production. It is a colourless liquid with a chloroform-like odour. 1,2-Dichloroethane is also used generally as an intermediate for other organic chemical compounds, and as a solvent.

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History

In 1794, a group of four Dutch friends under the name of Gezelschap der Hollandsche Scheikundigen (Society of Dutch Chemists) consisted of physician Jan Rudolph Deerman, merchant Adriaan Paets van Troopstwijkity, chemist Anthoni Lauwerenburgest and botanist Nicolaas Bondtitigutrud. They were the first to produce 1,2-dichloroethane from olefiant gas (oil-making gas, ethylene) and chlorine gas. Although the Gezelschap in practice didn't do much in-depth scientific research, they and their publications where highly regarded. Part of that acknowledgement is that 1,2-dichloroethane has been called Dutch oil in old chemistry.

Chemistry

1,2-Dichloroethane has chemical formula C₂H₄Cl₂.

Cf. 1,1-Dichloroethane (ethylidene dichloride).

Production

Every year 17.5 million tons of 1,2-dichloroethane are produced in the United States, Western Europe and Japan.^[1] This is primarily achieved through the iron(III) chloride catalysed reaction of ethene (ethylene) and chlorine.

H₂C=CH₂ + Cl₂ → Cl-CH₂-CH₂-Cl

In subsequent reactions, notably to vinyl chloride (chloroethene), hydrogen chloride is formed and re-used in a copper(II) chloride catalysed reaction, to also produce 1,2-dichloroethane from ethene and oxygen.

H₂C=CH₂ + 2 HCl + ½ O₂ → Cl-CH₂-CH₂-Cl + H₂O

Uses

Vinyl chloride monomer (VCM) production

With approximately 80% of the world's consumption of 1,2-dichloroethane, the major application is in the production of vinyl chloride monomer (VCM, chloroethene), which is the precursor to polyvinyl chloride under the formation of hydrogen chloride.

Cl-CH₂-CH₂-Cl → H₂C=CH-Cl + HCl

The hydrogen chloride can be re-used in the production process, in the formation of more 1,2-dichloroethane (see Production).

Other Uses

As a good apolar aprotic solvent, 1,2-dichloroethane is used as degreaser and paint remover. As a useful 'building block' reagent, it is used as an intermediate in the production of various organic compounds. It is also used as a reagent as an electrophillic source of chlorine, with elimination of ethene and chloride.

Historically, it was used as an anti-knock additive in leaded fuels.

Safety

1,2-dichloroethane is toxic (especially by inhalation due to its high vapour pressure), corrosive, highly flammable,^{[citation needed]} and possibly carcinogenic. Its high solubility and 50-year half-life in anoxic aquifers make it a perennial pollutant and health risk that is very expensive to treat conventionally, requiring a method of bioremediation.^[2]

References

1. ^ J.A. Field & R. Sierra-Alvarez (2004). "Biodegradability of chlorinated solvents and related chlorinated aliphatic compounds". Rev. Environ. Sci. Biotechnol. 3: 185-254.
2. ^ S. De Wildeman & W. Verstraete (25 Mar., 2003). "The quest for microbial reductive dechlorination of C2 to C4 chloroalkanes is warranted". Appl. Microbiol. Biotechnol. 61 (2): 94-102. doi:10.1007/s00253-002-1174-6.