Acetic acid

Acetic acid molecule

Acetic acid is a weak acid, and the defining ingredient in vinegar. Aside from its common use in food, acetic acid is an important industrial chemical. Its formulae is C₂H₄O_2.

In Situ Production

Biological Synthesis

Since prehistoric times, humans have produced acetic acid by exposing alcoholic beverages to aerobic bacteria usually of the acetobacter genus. The bacteria convert the alcohol to acetic acid. Distillation of the vinegar concentrates the acid.

Artificial Synthesis

There are several techniques used to produce acetic acid on an industrial scale.

Methanol Carbonylation

Methanol and carbon monoxide are combined under pressure, in the presence of a catalyst.

Ethylene Oxidation

Acetic Acid production process

Ethylene is oxidized in the presence of a palladium based catalyst.

Ethane Oxidation

Ethane is oxidized in the presence of a catalyst.

Use

Food Preservation

Though acetic acid is commonly generated by certain microbes, in high enough concentrations it preserves food.

Chemical Production

Acetic acid has the formula CH3COOH, and is used in the production of adhesives, inks, paints, acetic anhydride (used in synthetic textiles, photographic film, and flexible plastic type materials), it is an excellent polar protic solvent, and (its largest use on Earth) vinyl acetate monomer.

Medical Use

Since ancient times, it has been used as a medicine to reduce headaches and act is a weak blood thinner. See Aspirin.