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ethylene glycol

Product name ethylene glycol
Synonyms monoethylene glycol
1,2-ethanediol
MEG
GOST 19710-83
CAS 107-21-1

Ethylene glycol (MEG) is a colorless, viscous, hygroscopic liquid with a sweetish taste. It is fully miscible in water, lower alcohols and acetone; boundedly soluble in diethyl ether, carbon tetrachloride, benzene, toluene, chloroform. Mineral oils, polyvinyl chloride, paraffin, rubber are almost insoluble in ethylene glycol. MEG dissolves in water with liberaton of heat and contraction of volume. Its water solutions are characterized with low freezing point.

Ethylene glycol is a simplest diatomic alcohol (diol). It was first prepared in 1859 by the French chemist Charles-Adolphe Wurtz. MEG reacts with alkali metals and alkalis to form corresponding salts, which are known as glycolates. It can be esterified with organic acids or their anhydrides to give mono- and di- substituted esters. Ethylene glycol dehydrates in the presence of zinc chloride ZnCl2 resulting in acetaldehyde:

HOCH2CH2OH --> CH3CHO + H2O

Dehydration in alkaline media depending on conditions leads to 1,4-dioxane or diethylene glycol. Ethylene glycol reacts with ethylene oxide to form mixture of oligomers, such as diethylene glycol (DEG), triethylene glycol (TEG), tetraethylene glycol and polyethylene glycols. MEG can be used for carbonyl group protection in synthetic organic chemistry. Its reaction with carbonyl compounds results in five-member cyclic ethers 1,3-dioxolanes formation:

protection of carbonyl group by the reaction with ethylene glycol


Hydroxyl group in ethylene glycol can be substituted with chlorine or bromine by the action of corresponding hydrogen halide or phosphorus pentahalide. Being oxidized MEG forms a mixture of products: glycol aldehyde HOCH2CHO, glyoxal CHOCHO, hydroxiacetic (glycolic) acid HOCH2COOH, glyoxylic acid CHOCOOH and oxalic acid HOOCCOOH. The product ratio depends on reaction conditions.

Ethylene glycol is toxic, and the major danger from it is following ingestion. The result of poisoning is central nervous system and kidney injury.

Production.

Almost of industrial ethylene glycol production is based on the reaction of ethylene oxide hydration:

C2H4O + H2O --> HOCH2CH2OH

Process is conducted at 130-150°C, pressure 1.5-2MPa and 8-15 excess of water. The reaction can be catalyzed by either acids or bases, but this accelerates corrosion of equipment, or can occur at neutral pH under increased temperatures. The highest yields of ethylene glycol occur in acidic or neutral media. Under these conditions, ethylene glycol yields of 90% can be achieved. Basic contaminations of this reaction are MEG oligomers - diethylene glycol, triethylene glycol and other polyethylene glycols (PEG). Their content is increased with relative amount of ethylene oxide in the reaction mixture.

Uses.

  • MEG is widely used as an automotive antifreeze;
  • as a deicing fluid for windshields and aircraft;
  • as a component of hydraulic and hardening liquids;
  • in polyethylene terephthalate (PET) making. This is a important plastic, used to make plastic bottles for soft drinks and polyester fibers. PET is produced by condensation of terephthalic acid with ethylene glycol:

    PET making by condensation of terephthalic acid with ethylene glycol


  • as an intermediate for manufacturing of 1,4-dioxane, diethylene glycol and other ethylene glycol oligomers;
  • due to its hygroscopic property it is used as a dehydrating agent for gases;
  • for preparation of polyurethanes and alkyd resins;

  • Manufacturer(s) JSC "Nizhnekamskneftekhim" Inc.
    JSC Kazanorgsintez
    JSC Sibur-Neftehim
    Chemical structure of ethylene glycol

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