The
Chemical Compound ethylene oxide is an important industrial chemical used as an intermediate in the production of
Ethylene Glycol and other chemicals, and as a sterilant for foodstuffs and medical supplies. It is a colorless flammable gas or refrigerated liquid with a faintly sweet odor. It is the simplest example of an
Epoxide .
Its
IUPAC name is
1,2-epoxyethane. Other names for it include '''oxirane''' and '''dimethylene oxide'''.
History
Ethylene oxide was first prepared in
1859 by the
French chemist
Charles Wurtz , who prepared it by treating
2-chloroethanol with a
Base . It achieved industrial importance during
World War I as a precursor to both the coolant
Ethylene Glycol and the
Chemical Weapon Mustard Gas . In
1931 ,
Theodore Lefort , another French chemist, discovered a means to prepare ethylene oxide directly from
Ethylene and
Oxygen , using
Silver as a
Catalyst . Since
1940 , almost all ethylene oxide produced industrially has been made using this method.
Production
Industrially, ethylene oxide is produced when ethylene and oxygen react on a silver catalyst at 200–300 °C. Pressures used are in the region of 1-2MPa. The
Chemical Equation for this
Reaction is
:
CH2=CH2 + ½
O2 → C
2H
4O
The typical yield for this reaction is 70-80%, the major side reaction being
Combustion of ethylene to produce
Carbon Dioxide . Several methods to produce ethylene oxide more selectively have been proposed, but none have achieved industrial importance.
Uses
Ethylene oxide gas kills
Bacteria ,
Mold , and
Fungi , and can therefore be used to sterilize substances that would be damaged by sterilizing techniques such as
Pasteurization that rely on heat. Ethylene oxide sterilization for the preservation of
Spice s was patented in
1938 by the
American chemist
Lloyd Hall , and it is still used in that role. Additionally, ethylene oxide is widely used to sterilize medical supplies such as bandages, sutures, and surgical implements.
Most ethylene oxide, however, is used as an intermediate in the production of other chemicals. The major use of ethylene oxide is in the production of
Ethylene Glycol , which is widely used as an automotive coolant and
Antifreeze , and is also used to produce
Polyester polymers.
Reactions
Most reactions are ring openings by
Nucleophiles .
In industry, epoxyethane is reacted with
Water in the presence of a
Sulfuric Acid catalyst. A ten-fold molar excess of water is used to obtain ethylene glycol:
C
2H
4O + H
2O → HOCH
2CH
2OH
Despite the large excess of water, various types of
Polyethylene Glycol (PEG) or
Polyethylene Oxide (PEO) are still formed as secondary products. The degree of
Polymerization increases as a smaller proportion of water is used:
n(CH
2CH
2O) + H
2O → HO(CH
2CH
2O)
nH
For example, under the right conditions it can give diethylene glycol (HOCH
2CH
2OCH
2CH
2OH), triethylene glycol, etc.
Similarly, reaction with
Ammonia can yield
Ethanolamine , diethanolamine, or triethanolamine.
Ethylene oxide is also important in the manufacture of
Surfactant s and other
Detergent s, in a process called
Ethoxylation .
One class of ethylene oxide derivatives that has attracted much scientific attention is the
Crown Ether s, which are cyclic
Oligomer s of ethylene oxide. These compounds have the ability to make
Ionic Compound s such as
Salt s soluble in nonpolar
Solvent s which they otherwise could not dissolve in. However, the high cost of these compounds has largely confined their use to the laboratory rather than industrial practice.
Health effects
Ethylene oxide is toxic by inhalation. Symptoms of overexposure include headache and dizziness, progressing with increasing exposure to convulsions, seizure and coma. It is also an irritant to skin and the respiratory tract, and inhaling the vapors may cause the lungs to fill with fluid several hours after exposure.
Ethylene oxide is usually stored as a pressurized or refrigerated liquid. At room temperature and pressure, it rapidly evaporates, potentially causing frostbite in cases of skin exposure.
Laboratory animals exposed to ethylene oxide for their entire lives have had a higher incidence of
Liver Cancer . However, studies on human beings who have worked with ethylene oxide for extended periods and may have experienced low doses during that time have found no increase in cancer risk. Chronic ethylene oxide exposure may increase the risk of
Cataract s in humans.
In animals, ethylene oxide can cause numerous reproductive effects, including
Mutation s and a higher rate of
Miscarriage s. Its reproductive effects on humans have not been well studied, but it is considered probable that ethylene oxide exposure has similar effects on human reproduction.
See also
External links
