What Is Allyl Alcohol?
Allyl alcohol is an unsaturated alcohol with the simplest structure, represented by the structural formula CH2=CHCH2OH.
Other names include 2-propene-1-ol, propenyl alcohol, and 3-hydroxypropene. The unsaturated alcohol with the lowest molecular weight in its structural formula is vinyl alcohol (CH2＝CHOH), but vinyl alcohol isomerizes to acetaldehyde (CH3COH), which is a more stable structure, making substantial allyl alcohol the lowest molecular weight unsaturated alcohol.
Uses of Allyl Alcohol
Allyl alcohol is used in a variety of fields as a raw material for various synthetic applications. In the chemical field, it is useful as an intermediate in the synthesis of epichlorohydrin, allyl glycidyl ethers, and propanesultone.
It is also used as a raw material for diallyl phthalate resin, resin additives, and allyl compounds such as glycerol. It is also used as a raw material for pharmaceuticals, fragrances, agrochemicals, fungicides, and flame retardants.
Properties of Allyl Alcohol
Allyl alcohol is a clear, colorless liquid with a molecular weight of 58.08 and a strong pungent odor. It has a density of 0.854 g/cm3, a melting point of -129°C, a boiling point of 97°C, a flash point of 21°C, an ignition temperature of 443°C, and a refractive index of 1.4134.
It is extremely soluble in water, soluble in ethanol, chloroform, and ether, and flammable. Inhalation of allyl alcohol vapor has a strong effect on the eyes and nose, and is designated as a Class I Designated Chemical Substance under the Chemical Substances Control Law and as a toxic substance under the Poisonous and Deleterious Substances Control Law.
Because of its high flammability, it is classified as a Class 4 Hazardous Substance, Class 2 Petroleum Soluble in Water under the Fire Service Law, and its handling and storage quantity are restricted. In addition, it is designated as a flammable hazardous substance, a hazardous substance that should be labeled or notified by name, and a toxic substance under the Industrial Safety and Health Law.
Other Information on Allyl Alcohol
1. Manufacturing Process of Allyl Alcohol
Industrial methods include isomerization of propylene oxide and direct oxidation of propylene. There are several other synthetic methods, including the allyl chloride method, the acrolein method, the propylene oxide method, and the allyl acetate method.
Propylene Oxide Isomerization
CH2CH(CH3)O → CH2＝CHCH2OH
Propylene oxide is isomerized by heating in the presence of potassium aluminum sulfate to produce allyl alcohol.
Direct Oxidation of Propylene
CH3CH=CH2 + CH3COOH + 1/2O2 → CH2= CHCH2OCOCH3 + H2O
CH2= CHCH2OCOCH3 ＋ H2O → CH2＝CHCH2OH + CH3COOH
Propylene, acetic acid, and oxygen react to form allyl alcohol. This reaction is one of the methods to directly synthesize allyl alcohol from propylene, and by optimizing the reaction conditions, allyl alcohol can be obtained in high yield.
Acid Catalyzed Oxidation
Propylene is oxidized in the presence of strong acids such as phosphoric acid and sulfuric acid to produce allyl alcohol, allyl aldehyde, and allylic acid. Allyl alcohol must be separated and purified by post-treatment.
Hydrolysis of Allyl Chloride
CH2=CHCH2Cl + H2O → CH2=CHCH2OH + HCl
Allyl alcohol is obtained by hydrolysis of chloroaryl.
2. Precautions for Handling Allyl Alcohol
Allyl alcohol has a strong pungent odor and should be handled with care. It may also react with strong oxidizing agents, causing an explosive reaction, so adequate safety measures are essential when handling it.
Since it is irritating to skin and mucous membranes, appropriate protective equipment such as rubber gloves, protective glasses, and masks should be worn when handling. In addition, allyl alcohol dissolves well in water, so adequate ventilation is required when handling it. If it comes in contact with skin or mucous membranes, rinse immediately with running water and consult a physician.
The product is highly volatile and flammable. Due to its low flash point of 22°C, it is important to keep it away from fire and heat sources. Storage away from corrosive and oxidizing materials is also recommended.