Styrene oxide is an organic compound with the molecular formula C8H8O
and the IUPAC name phenyloxirane. It is an epoxide derived from
styrene, which is a common monomer used to make polystyrene and other
plastics. Styrene oxide has a chiral center at the benzylic carbon atom,
so it exists as two enantiomers: ®-styrene oxide and (S)-styrene oxide.
Styrene oxide belongs to the class of oxiranes, which are
three-membered cyclic ethers with one oxygen atom and two carbon atoms.
Styrene oxide is a colorless to light yellow liquid with a sweet
odor. It is slightly soluble in water and miscible with most organic
solvents. It is unstable and reactive, and can undergo polymerization,
hydrolysis, isomerization, ring-opening, and other reactions. It is also
toxic and carcinogenic, and can cause irritation and sensitization to
the skin, eyes, and respiratory tract.
Styrene oxide is mainly used as an intermediate in the synthesis of
various chemicals, such as styrene glycol, phenethyl alcohol,
phenylacetaldehyde, and other derivatives. These chemicals are further
used in the production of fragrances, flavors, pharmaceuticals,
pesticides, polymers, and other products. Styrene oxide can also be used
as a reactive diluent in epoxy resins or as a modifier for unsaturated
polyester resins.
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Color: Colorless to light yellow
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Shape: Liquid
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Odor: Sweet
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Density: 1.054 g/mL at 25 °C
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Melting point: -37 °C
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Boiling point: 194 °C
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Flash point: 79 °C
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Vapor pressure: 0.7 mmHg at 20 °C
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Vapor density: 4.14 (air = 1)
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Solubility in water: 3 g/L at 20 °C
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Refractive index: 1.535 at 20 °C
The following are some of the chemical properties of styrene oxide:
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Stability: Styrene oxide is unstable and prone to polymerization
with compounds possessing a labile hydrogen (such as acids and alcohols)
in the presence of acids, bases or some salts. It is also sensitive to
moisture and heat, and can decompose violently when heated above 200 °C
or under UV light.
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Reactivity: Styrene oxide is highly reactive and can undergo various
reactions, such as hydrolysis, isomerization, ring-opening, addition,
substitution, oxidation, reduction, and elimination. Some of the common
reactions are:
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Hydrolysis: Styrene oxide can be hydrolyzed by water or acids to
form racemic phenylethyleneglycol or phenylacetaldehyde, depending on
the amount of water and the pH.
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Isomerization: Styrene oxide can be isomerized by acids or bases to form phenylacetaldehyde or phenylacetic acid.
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Ring-opening: Styrene oxide can be opened by nucleophiles (such as
alcohols, amines, thiols, halides) to form various alkoxy-, amino-,
thio-, or halo-substituted ethylbenzenes.
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Addition: Styrene oxide can be added by electrophiles (such as
hydrogen halides, sulfuric acid) or radicals (such as bromine) to form
halogenated or sulfonated ethylbenzenes.
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Substitution: Styrene oxide can be substituted by nucleophiles
(such as cyanide, azide) or electrophiles (such as nitric acid) to form
nitrile-, azido-, nitro-, or nitrate-substituted ethylbenzenes.
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Oxidation: Styrene oxide can be oxidized by strong oxidizing
agents (such as permanganate, chromate, hydrogen peroxide) to form
benzoic acid or phenylglyoxylic acid.
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Reduction: Styrene oxide can be reduced by hydrogen or hydride
donors (such as sodium borohydride, lithium aluminum hydride) to form
phenethyl alcohol or phenylethylamine.
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Elimination: Styrene oxide can be eliminated by bases (such as
sodium hydroxide, potassium carbonate) to form styrene or vinylbenzene.
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Acidity and basicity: Styrene oxide is neither acidic nor basic, but
it can act as a Lewis acid or a Lewis base, depending on the reaction
conditions and the reagents involved. For example, it can coordinate
with Lewis bases (such as amines, phosphines) to form complexes, or it
can accept electrons from Lewis acids (such as boron trifluoride,
aluminum chloride) to form adducts.
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Redox potential: Styrene oxide has a moderate redox potential and
can be oxidized or reduced by various reagents. The standard electrode
potential of styrene oxide/styrene couple is -0.62 V (vs. SHE) at 25 °C
and pH 7.
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Flammability and explosiveness: Styrene oxide is combustible and can
form explosive mixtures with air. The lower and upper explosive limits
are 1.1% and 22% (v/v), respectively. The autoignition temperature is
500 °C.
Styrene oxide Synthesis methods
Styrene oxide can be synthesized by various methods, such as:
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Epoxidation of styrene: This is the most common and industrial
method for producing styrene oxide. Styrene can be epoxidized by
different oxidizing agents, such as peracids (perbenzoic acid, peracetic
acid, performic acid), hydrogen peroxide, oxygen, ozone, or metal
oxides (molybdenum trioxide, vanadium pentoxide). The epoxidation can be
catalyzed by various catalysts, such as acids, bases, metal salts,
metal complexes, enzymes, or zeolites. The epoxidation can be performed
in different solvents, such as chloroform, acetone, acetonitrile, or
water. The epoxidation can produce either racemic or enantioselective
styrene oxide, depending on the choice of oxidizing agent, catalyst,
solvent, and reaction conditions.
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Oxidation of ethylbenzene: This is an alternative method for
producing styrene oxide. Ethylbenzene can be oxidized by oxygen or air
in the presence of a cobalt catalyst to form styrene oxide and
acetaldehyde. The oxidation can be performed in a gas phase or a liquid
phase reactor at high temperature and pressure.
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Other methods: Styrene oxide can also be synthesized by other methods, such as:
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Hydroxylation of styrene: Styrene can be hydroxylated by hydrogen
peroxide in the presence of a titanium catalyst to form phenylethylene
glycol, which can then be dehydrated by sulfuric acid to form styrene
oxide.
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Chlorohydrination of styrene: Styrene can be chlorohydrinated by
chlorine and water in the presence of an iron catalyst to form
2-chloroethylbenzene, which can then be dehydrochlorinated by sodium
hydroxide to form styrene oxide.
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Bromination of ethylbenzene: Ethylbenzene can be brominated by
bromine in the presence of light to form 1-bromoethylbenzene, which can
then be dehydrobrominated by sodium hydroxide to form styrene oxide.
Styrene oxide Applications and effects
Styrene oxide has various applications and effects in different fields
Organic synthesis: Styrene oxide is an important intermediate for
organic synthesis and can be used to prepare various chemicals, such as:
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Styrene glycol: This is the main product of the hydrolysis of
styrene oxide and can be used as a solvent, a plasticizer, a surfactant,
or a precursor for other chemicals.
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Phenethyl alcohol: This is the main product of the hydrogenation of
styrene oxide and can be used as a fragrance ingredient, a
preservative, an antiseptic, or a precursor for other chemicals.
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Phenylacetaldehyde: This is the main product of the isomerization
of styrene oxide and can be used as a flavor ingredient, a perfume
ingredient, or a precursor for other chemicals.
Chemical industry: Styrene oxide is an important raw material for the
chemical industry and can be used to produce various polymers, such as:
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Epoxy resins: Styrene oxide can be used as a reactive diluent or a
modifier for epoxy resins, which are widely used as adhesives, coatings,
composites, and electrical insulators.
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Unsaturated polyester resins: Styrene oxide can be used to modify
the properties of unsaturated polyester resins, which are commonly used
as plastics, fiberglass, and gel coats.
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Polyamides: Styrene oxide can be used to synthesize polyamides,
which are synthetic polymers with high strength, toughness, and
resistance to heat and chemicals.
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Polyurethanes: Styrene oxide can be used to prepare polyurethanes,
which are versatile polymers with various applications in foams,
elastomers, coatings, and adhesives.
Pharmaceutical industry: Styrene oxide is an intermediate for the
pharmaceutical industry and can be used to synthesize various drugs,
such as:
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Antihistamines: Styrene oxide can be used to produce
antihistamines, which are drugs that block the action of histamine and
relieve allergic symptoms.
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Antidepressants: Styrene oxide can be used to make antidepressants,
which are drugs that affect the mood and behavior by altering the
levels of neurotransmitters in the brain.
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Anticonvulsants: Styrene oxide can be used to create
anticonvulsants, which are drugs that prevent or reduce the frequency
and severity of seizures.
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Analgesics: Styrene oxide can be used to generate analgesics, which
are drugs that relieve pain by blocking the transmission of pain
signals.
Fragrance and flavor industry: Styrene oxide is an intermediate for
the fragrance and flavor industry and can be used to produce various
ingredients, such as:
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Phenethyl alcohol: This is a fragrance ingredient with a rose-like
odor and a flavor enhancer with a honey-like taste. It is widely used in
perfumes, cosmetics, foods, and beverages.
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Phenylacetaldehyde: This is a fragrance ingredient with a
hyacinth-like odor and a flavor enhancer with a floral taste. It is
commonly used in perfumes, cosmetics, foods, and beverages.
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Other derivatives: Styrene oxide can also be used to prepare other
derivatives with different odors and tastes by various reactions, such
as ring-opening, addition, substitution, oxidation, reduction, or
elimination. These derivatives include alkoxy-, amino-, thio-, halo-,
nitrile-, azido-, nitro-, nitrate-, sulfonated ethylbenzenes.
Environmental effects: Styrene oxide has negative effects on the
environment and can cause harm to aquatic life and soil organisms. It is
toxic to fish, algae, bacteria, fungi, earthworms, and plants. It can
bioaccumulate in aquatic organisms and biomagnify in the food chain. It
can also degrade into more toxic compounds in the environment.
Health effects: Styrene oxide has adverse effects on human health and
can cause damage to various organs and systems. It is toxic by
inhalation, ingestion, or skin contact. It can cause irritation and
sensitization to the skin, eyes, and respiratory tract. It can also
cause drowsiness or dizziness. It is suspected of causing genetic
defects, damaging fertility or the unborn child. It is known to cause
cancer.
Styrene oxide Safety precautions
Styrene oxide is a hazardous substance that requires special
precautions for handling, storage, and disposal. Some of the safety
measures are:
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Handling: Work under hood. Do not inhale substance/mixture. Avoid
generation of vapors/aerosols. Use personal protective equipment as
required. Wear protective gloves/protective clothing/eye protection/face
protection. Wash hands thoroughly after handling. Do not eat, drink or
smoke when using this product. Contaminated work clothing should not be
allowed out of the workplace.
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Storage: Store locked up. Store in a well-ventilated place. Keep
container tightly closed. Keep away from heat/sparks/open flames/hot
surfaces. Do not expose to light or moisture.
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Disposal: Dispose of contents/container to an approved waste
disposal plant. Do not release into the environment. Follow local
regulations for waste disposal.
