This antioxidant is contained in food, adhesive glues,
industrial oils, and greases, including cutting fluids.
Sensitization seems very rare.
Routes of Entry:
Absorbed through skin. Dermal contact. Inhalation. Ingestion.
Toxicity to Animals:
Acute oral toxicity (LD50): 650 mg/kg [Mouse].
Air & Water Reactions
Insoluble in water.
White crystalline solid.
1.Industrially, BHT is prepared by the reaction of p-cresol (4-methylphenol) with isobutylene (2-methylpropene) catalyzed by sulfuric acid:
CH3(C6H4)OH + 2 CH2=C(CH3)2 → ((CH3)3C)2CH3C6H2OH
Isobutene is added in the (98:2) mixture of p-cresol and concentrated sulfuric acid. The reaction is carried out at 65~70 ℃ for 5h. The acid in the mixture is washed away with water of 60 ℃. The mixture is then washed with 10% NaOH solution and hot water to obtain the neutral crude product. The crude product is dissolved in hot 50% alcohol along with 0.5% of sulfocarbamide. Filtration and spin-drying is carried out when the liquid is still hot. The finished product is obtained through the following desiccation. In this routine, the productivity rate is as high as and the product purity is with melting point of over 69.5℃.
In industry, the cascading main-vice tower technology is usually adapted. P-cresol and catalysts are put in the main and vice towers. The temperature in the main tower is maintained at 65～80℃ while that in the vice tower at 50～70℃. Isobutene gas is pumped in from the bottom, the majority of which react with p-cresol and the rest of which is let into the vice tower for further reaction with p-cresol. The reaction cycle in the main tower lasts for 4～5h. On the end of the reaction, isobutene gas is cut off and NaOH solution (20%) is added. Compressed air is pumped in to bubble the solution. The neutralized crude alkylation product is extracted through distillation tower with 8 theoretical plates. The crude product is then dissolved in 95% alcohol and separated from mineral salts using ion exchange followed by refrigeration crystallization at 10～20℃, separation and vacuum drying to obtain the finished product with its melting point at over 69℃.
2.In another synthesis routine, p-cresol and tert.-butyl alcohol are mixed in their molar ratio of 1：1.1. Under the catalysis of ortho-phosphoric acid, the react is conducted at 65～70℃ with intense stirring. The product is washed with caustic soda solution to reach certain basicity and then washed into neutral with water. The dissolvent is then removed and the product is obtained through recrystallization with alcohol.
3.Alternatively, BHT is prepared from 2,6-di-tert-butylphenol by hydroxymethylation or aminomethylation followed by hydrogenolysis.
Internal standard solution: Dissolve 500mg of diphenylamine or 4-tert butyl phenol in acetone and dilute with it to 250mL.
Standard solution ：Dissolve 100mg of BHT in acetone and dilute with it to 50mL.
Determination: Dissolve 100mg of the sample in internal standard solution and dilute with it to 50mL. The sample solution is put into a gas chromatograph equipped with a hydrogen flame ion detector. A column (1.5 m x 3 mm ID) containing 10% XE-60 at 100 to 200 mesh Aeropak 30 is kept at an constant temperature of 155 ° C. The temperature of the injector and the detector ss 225 ° C and 250 ° C, respectively. The determination is conducted with nitrogen carrier gas whose flow velocity is 30ml/min.
The standard curves are drawn according to the peak height of various concentrations of BHT and internal standard solution, and then the reference standard curve is used to determine the content of BHT.
Antioxidant 264 as general antioxidants is used widely in polymer materials, petroleum products and food processing industries. Antioxidant 264 is commonly used rubber antioxidant, heat, oxygen aging have some protective effect, but also can inhibit copper harm. This product does not change color, not pollution. Antioxidants 264 high solubility in oil, no precipitation, less volatile, non-toxic and non-corrosive.
Phenols, such as 2,6-Di-tert-butyl-4-methylphenol, do not behave as organic alcohols, as one might guess from the presence of a hydroxyl (-OH) group in their structure. Instead, they react as weak organic acids. Phenols and cresols are much weaker as acids than common carboxylic acids (phenol has Ka = 1.3 x 10^[-10]). These materials are incompatible with strong reducing substances such as hydrides, nitrides, alkali metals, and sulfides. Flammable gas (H2) is often generated, and the heat of the reaction may ignite the gas. Heat is also generated by the acid-base reaction between phenols and bases. Such heating may initiate polymerization of the organic compound. Phenols are sulfonated very readily (for example, by concentrated sulfuric acid at room temperature). The reactions generate heat. Phenols are also nitrated very rapidly, even by dilute nitric acid. Nitrated phenols often explode when heated. Many of them form metal salts that tend toward detonation by rather mild shock. May react with oxidizing materials.
ChEBI: A member of the class of phenols that is 4-methylphenol substituted by tert-butyl groups at positions 2 and 6.
Dissolve BHT in n-hexane at room temperature, then cool with rapid stirring, to -60o. The precipitate is separated, redissolved in hexane, and the process is repeated until the mother liquor is no longer coloured. The final product is stored under N2 at 0o [Blanchard J Am Chem Soc 82 2014 1960]. It has also been recrystallised from EtOH, MeOH, *benzene, n-hexane, methylcyclohexane or pet ether (b 60-80o), and is dried in a vacuum. [Beilstein 6 IV 3511.]
- Suitable extinguishing media
- Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
- Special protective equipment for fire-fighters
- Wear self contained breathing apparatus for fire fighting if necessary.
Physical State: Solid /Crystal
Appearance: White. It turns yellow in the presence of light and gradually becomes darker.
Odor: Faint, characteristic odor.
Vapor Pressure: 0.01 mm Hg at 20 ?C
Vapor Density: 7.6
Viscosity: 3.47cSt at 20 ?C
Boiling Point: 265 ?C
Freezing/Melting Point: 70 ?C
Solubility: Insoluble in water and soluble in benzene, methylbenzene, methanol, methyl ethyl ketone, ethanol, isopropanol, petroleum ether and flaxseed oil.
Specific Gravity/Density: 1.048
Molecular Formula: C15H24O
Molecular Weight: 220.35
General Phenolic Antioxidant
Antioxidant 264 is an excellent general type of phenolic antioxidants with no toxicity, no flammability, no corrosion and excellent storage stability. It can inhibit and delay the oxidation-degradation of plastic or rubber and prolong their service life.
2,6-Di-tert-butyl-4-methylphenol is combustible.
Antioxidant for food, animal feed, petroleum products, synthetic rubbers, plastics, animal and vegetable oils, soaps. Antiskinning agent in paints and inks.
Handling and Storage
Precautions for safe handling
Avoid contact with skin and eyes. Avoid formation of dust and aerosols.
Provide appropriate exhaust ventilation at places where dust is formed.
Normal measures for preventive fire protection.
Conditions for safe storage
Keep container tightly closed in a dry and well-ventilated place.Keep in a dry place.
BHT is listed under three categories in catalogues and databases, such as food additive, household product ingredient, industrial additive, personal care product/cosmetic ingredient, pesticide ingredient, plastic/Rubber ingredient and Medical/Veterinary/Research
BHT is primarily used as an antioxidant food additive. In the United States, it is classified as generally recognized as safe (GRAS) based on a National Cancer Institute study from 1979 in rats and mice. It is approved for use in the U.S. by the Food and Drug Administration: For example, 21 CFR § 137.350(a)(4) allows BHT up to 0.0033% by weight in "enriched rice", while 9 CFR § 381.147(f)(1) allows up to 0.01% in poultry "by fat content". It is permitted in the European Union under E321. It is forbidden as food additive in Japan (since 1958), Romania, Sweden, and Australia. Since the 1970s, BHT has been steadily replaced with butylated hydroxyanisole (BHA). Some food companies have voluntarily eliminated BHT from their products. Others like General Mills and Kellogg's announced in February 2015, following a petition by Vani Hari, that they were going to phase it out.
BHT is also used as an antioxidant in products such as cosmetics, pharmaceuticals, rubber, electrical transformer oil (at 0.35%),and embalming fluid. In the petroleum industry, where BHT is known as the fuel additive AO-29, it is used in hydraulic fluids, turbine and gear oils, and jet fuels. BHT is also used to prevent peroxide formation in diethyl ether and other laboratory chemicals. As rubber antioxidant, BHT can protect rubber from heat and oxidation aging as well as control the harm from copper. It is also applied as stabilizer used on synthesized rubber in the handling and storage.
BHT can be applied by dip-moulding, direct mixing, nebulization and indirect mixing in alcobolic solution.
Some additive products contain BHT as their primary ingredient, while others contain the chemical merely as a component of their formulation, sometimes alongside butylated hydroxyanisole (BHA).
- FAO/WHO(1984，mg/kg)： 200 in general edible oils and fats， 200 in butter oil ( not allowed in direct consumption and recombined milk), 100 in margarine.
- In Japan (g/kg)： 0.2 in grease and pickled fishes， 1 in impregnation liquid for frozen fishes， 0.75 in gum confection.
- USDA (9CFR， §318．7， §381．147，2000%)： 0.003 in dry sausage； 0.01 in refined animal oil； 0.02 in margarine； 0.01 in poultry (calculated by fat content).
- FDA (21CFR， §172．115， §172．615，§173．340，§181．24， §182．3173； §172．515；2000，mg/kg) 50 in dehydrated potato and cereal； 0.1% in defoamer； 0.005％ migrated from packaging material for food； 0.5% in essential oil； 0.1% in gum base；0.02% in fat food.
- EEC-HACSG：not allowed in infantal food except used for the supplement of vitamin A.
white crystalline solid