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Ethylene oxide

What is ethylene oxide?

Ethylene oxide is a cyclic ether or simple epoxide compound with the molecular formula C2H4O. In ethylene oxide structure, an oxygen atom is linked to the two carbon atoms with a three-member cyclic ring. It is a colourless gas with a boiling point of 10.7 °C. The viscosity of liquid ethylene oxide is much lower than that of water. Industrially, it has been produced by passing ethylene and air under pressure over a silver catalyst at 200 to 400 °C. A large volume of EtO is used for making different chemicals like ethylene glycol, cellosolve, etc. It is also used for the sterilization of medical equipment.

Chemical structure and formula of ethylene oxide

According to the IUPAC system of nomenclature, it is denoted by the prefix epoxy. Thus, EtO is called epoxyethane. It is named oxiran due to the presence of the oxiran ring. Oxiran compounds are also referred to as cyclic ethers or alkenes oxides.

Properties
Chemical formula C2H4O
IUPAC name Epoxyethane
Oxacyclopropane
Molar mass 44.052 g/mol
Density 0.8821 g/cm3
Melting point −112.46 °C
Boiling point 10.4 °C
Dipole moment 1.94 D
Heat capacity 47.9 J mol−1 K−1

Ethylene oxide production

Ethylene oxide production from ethylene and 2-chloroethanol

Oxidation of ethylene by peroxy acids

Ethylene oxide is prepared by epoxidation of alkenes like ethylene with peroxy acids. Peroxybenzoic acid (C6H5COO2H), meta-chloro-peroxybenzoic acid, monoperoxyphthalic acid, and p-nitro-peroxybezoic acid are used for epoxidation. Emmons has found that peroxy trifluoroacetic acid is a very good reagent for epoxidation and hydroxylation. It is converted double bond of ethylene into an epoxide.

Industrial production

It is manufactured by passing ethylene and air under pressure over a chemical catalyst like silver at 200 to 400 °C.

Dehydrochlorination of 2-chloroethanol

It can be prepared by dehydrochlorination of 2-chloroethanol at elevated temperature, and beside sodium hydroxide or potassium hydroxide, calcium hydroxide, barium hydroxide, magnesium hydroxide, or carbonates of alkali or alkaline earth metals.

Chemical reaction

Molecular rearrangement

It undergoes molecular rearrangement on heating to form acetaldehyde.

Reduction reaction

It is symmetrical epoxide that is reduced by lithium aluminum hydride to form ethyl alcohol. For unsymmetrical epoxides, the main product is more highly substituted alcohol. It is readily reduced to the corresponding alkenes by t-phosphines.

Dimerization

In presence of dilute sulfuric acid, it dimerizes to form dioxan. Dioxan is a useful solvent for cryoscopic and ebullioscopy work.

Methyl cellosolve

Methyl cellosolve or monomethyl ether is prepared by heating ethylene oxide with methanol under pressure. Cellosolves are very useful solvents since they contain both alcohol and ether functional groups.

Ethylene oxide to ethylene glycol

Ethylene oxide is converted into ethylene glycol in a dilute acid solution. It also produced mono-ethers with alcohol in presence of a small amount of acid. The mechanism of the reaction in acid media follows the steps given in the picture.

Ethylene oxide to ethylene glycol preparation and mechanism

Ethylene oxide uses

  • Ethylene dioxide, most impotent intermediate used for the production of different types of industrial organic compounds. It is used mainly for the production of ethylene glycol.
  • When ethylene oxide heated is heated with methanol under pressure, the monomethyl ether of glycol is formed. It is known as methyl cellosolve. The corresponding ethyl ether is known as ethyl cellosolve. Cellosolves are very useful solvents due to the presence of alcohol and ether functional groups.
  • The direct use of ethylene oxide is very low due to health hazards and reactivity. It is readily flammable in the air. Directly, it is used as a sterilizing agent, disinfecting agent, and fumigant. For gas-phase sterilization of medical equipment and instruments, packaging materials and clothing, surgical and scientific equipment, we used ethylene oxide.
  • It reacts with ammonia to form a mixture of three amino alcohol which are usually referred to as ethanolamines. It is widely used for the preparation of emulsion.
  • It is used as a fungicide. Ethylene oxide is used to accelerate the maturation of tobacco leaves.