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Butylated Hydroxytoluene (BHT), designated as E321 in the European food additive system, is a synthetic antioxidant.
It is commonly used to prevent oxidation in fats and oils, extending the shelf life of food, cosmetics, pharmaceuticals, rubber, and petroleum products.
BHT works by scavenging free radicals, thus inhibiting the oxidative degradation of materials.
Cas Number
128-37-0
Synonyms
BHT,Butylated hydroxytoluene,2,6-Bis(1,1-dimethylethyl)-4-methylphenol,Ionol,Avox B
EMBANOX BHT,Uviox BHT
Introduction
Definition of E321 / BHT
Butylated hydroxytoluene (BHT), also known as E321 in the European food additive index, is a synthetic organic compound that acts as a potent antioxidant.
It belongs to the class of phenolic antioxidants, commonly used to preserve fats and oils by preventing oxidative rancidity.
BHT delays or inhibits the deterioration of products caused by exposure to oxygen.
Historical Background
BHT was first synthesized in the early 1940s and introduced as a food additive by the 1950s.
Initially used in rubber and petroleum industries, its efficacy in protecting food lipids led to its adoption in food processing.
Over the decades, its utility has expanded to cosmetics, pharmaceuticals, and polymers.
Regulatory Identifiers
IUPAC Name: 2,6-di-tert-butyl-4-methylphenol
E Number: E321
CAS Number: 128-37-0
EC Number: 204-881-4
Molecular Formula: C₁₅H₂₄O
Chemical Structure and Properties
Molecular Formula and Weight
BHT’s molecular formula is C₁₅H₂₄O, and its molecular weight is 220.35 g/mol.
Chemical Structure
The compound has a phenolic ring with methyl and tert-butyl substituents that provide steric hindrance, enhancing its oxidative stability.
Physical Properties
Appearance: White or pale yellow crystalline solid
Melting Point: 69–70°C
Boiling Point: 265°C
Solubility: Soluble in alcohol, ether, and fats; insoluble in water
Chemical Properties
BHT is lipophilic and stable in neutral to alkaline conditions. It resists oxidation due to the bulky tert-butyl groups.
Reactivity
It reacts with free radicals, forming a stable phenoxyl radical, effectively halting oxidative chain reactions in food systems.
Synthesis and Production
Industrial Synthesis
BHT is synthesized by alkylating p-cresol with isobutylene in the presence of an acid catalyst such as sulfuric acid.
Reaction Mechanism
The electrophilic aromatic substitution mechanism involves the methylation of the phenol ring at ortho positions by tert-butyl groups.
Raw Materials and Inputs
p-Cresol: A methylated phenol
Isobutylene: A gaseous alkene
Catalysts: Acid catalysts or zeolites
Purification and Quality Control
Post-reaction, the product is purified via crystallization, washed with solvents, and tested for residual monomers and purity (typically >99%).
Applications
Food Industry
Used as a preservative in:
Edible fats and oils
Breakfast cereals
Snacks
Chewing gum
It prevents rancidity and extends shelf life.
Cosmetics and Pharmaceuticals
Stabilizer in lipsticks, creams, moisturizers
Used in vitamins A and E supplements to prevent degradation
Prevents oxidation of active pharmaceutical ingredients
Industrial Uses
Protects rubber and plastics from degradation
Used in lubricating oils and biodiesel
Prevents color and viscosity changes due to oxidation
Mechanism of Action
Antioxidant Function
BHT donates a hydrogen atom from its hydroxyl group to neutralize free radicals, thus terminating oxidative chain reactions.
Inhibition of Oxidative Rancidity
In food systems, BHT interrupts the peroxidation of unsaturated fatty acids by forming stable radicals.
Synergistic Mechanisms
BHT is often combined with BHA and citric acid, which regenerates its antioxidant capacity and enhances overall protection.
SAFETY INFORMATION ABOUT E321 (BUTYLHYDROXYTOLUENE)
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off contaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
