What Is Acetaldehyde?
Acetaldehyde is an organic compound, an aldehyde with the chemical formula C2H4O.
Its IUPAC nomenclature name is ethanal, and another name for it is ethylaldehyde.
It has a molecular weight of 44.05, a melting point of -123°C, and a boiling point of 20.1°C. It is a clear, colorless liquid at room temperature with a putrid smell. Its density is 0.790 g/cm3 (at 10°C), and it is extremely soluble in water and solvents such as ethanol and diethyl ether.
Uses of Acetaldehyde
The main uses of acetaldehyde include as a raw material for manufacturing various organic compounds like acetic acid, aldehydes, antifungal agents, antiseptics, solvents, photo-developing chemicals, fuel blending agents, reducing agents, and medical chemicals.
It is used to synthesize pentaerythritol, crotonaldehyde, glyoxal, pyridine, acetonitrile, and acetic acid.
Principle of Acetaldehyde
The principle of acetaldehyde includes aspects of production and chemical reaction:
1. Production of Acetaldehyde
Acetaldehyde is industrially obtained by Wacker oxidation of ethylene.
2. Chemical Reaction of Acetaldehyde
Acetaldehyde is primarily used in the industrial synthesis of ethyl acetate by the Tishchenko reaction. In this reaction, two acetaldehyde molecules disproportionate into a carboxylic acid and an alcohol using an alkoxide as a catalyst, forming ethyl acetate by dehydration condensation.
It was previously used for synthesizing acetic acid but is now less common due to more efficient methods using methanol or acetylene.
3. Chemical Properties of Acetaldehyde
Acetaldehyde is a volatile substance with a low boiling point of 20.1℃ and exhibits keto-enol tautomerism. It is primarily in the keto form, with an equilibrium constant at room temperature of 6 × 10-5.
With a flash point of -38 ºC, it is highly flammable. It may form explosive peroxides in contact with air and react explosively with substances like oxygen, cobalt chloride, dinitrogen pentoxide, mercury chlorate, mercury perchlorate, silver nitrate, and hydrogen peroxide.
In the presence of trace metals, it may polymerize due to acids and alkaline hydroxides. It acts as a reducing agent and can pose a fire and explosion hazard when reacting with oxidants, strong acids, halogens, and amines.
4. Acetaldehyde and the Human Body
Acetaldehyde has a distinctive odor and irritating properties. It is an air pollutant derived from automobile exhaust, cigarette smoke, and glue used in plywood. Exposure to high amounts can be harmful, increasing cancer risk. It is one of the causative agents of sick building syndrome.
In the body, acetaldehyde is produced by alcohol dehydrogenase in the liver when ethanol is ingested, and is metabolized to acetic acid by acetaldehyde dehydrogenase.
Acetaldehyde is known for causing hangover symptoms. Its metabolism varies depending on race and constitution, influencing alcohol consumption constitution.
Types of Acetaldehyde
Acetaldehyde is sold as a reagent product for research and development and as a raw material for industrial organic synthesis.
Reagent products are available in capacities like 100mL, 500mL, 1L, and 500g. Industrial chemicals are available in larger capacities such as 14 kg canister cans.