Acetic acid

About the product
Acetic acid

Acetic acid is an organic compound with the chemical formula CH3CO2H (also written as CH3COOH). It is a colourless liquid that when undiluted is also called glacial acetic acid.

Acetic acid is the main component of vinegar (apart from water; vinegar is roughly 5% acetic acid by volume), and has a distinctive sour taste and pungent smell. It is mainly produced as a precursor to polyvinylacetate and cellulose acetate. Although it is classified as a weak acid, concentrated acetic acid is corrosive, and attacks the skin.

Acetic acid is one of the simplest carboxylic acids. It is an important chemical reagent and industrial chemical, mainly used in the production of cellulose acetate mainly for photographic film and polyvinyl acetate for wood glue, as well as synthetic fibres and fabrics. In households, diluted acetic acid is often used in descaling agents.

At physiological pHs, acetic acid is usually fully ionized to acetate. In biochemistry, acetate and acetic acid are equivalent.

Applications

Acetic acid is a chemical reagent for the production of chemical compounds. The largest single use of acetic acid is in the production of vinyl acetate monomer, closely bfollowed by acetic anhydride and ester production. The volume of acetic acid used in vinegar is comparatively small.

Use as solvent

Glacial acetic acid is an excellent polar protic solvent, as noted above. It is frequently used as a solvent for recrystallization to purify organic compounds. Acetic acid is used as a solvent in the production of terephthalic acid (TPA), the raw material for polyethylene terephthalate (PET). In 2006, about 20% of acetic acid is used for TPA production.

Acetic acid is often used as a solvent for reactions involving carbocations, such as Friedel-Crafts alkylation. For example, one stage in the commercial manufacture of synthetic camphor involves a Wagner-Meerwein rearrangement of camphene to isobornyl acetate; here acetic acid acts both as a solvent and as a nucleophile to trap the rearranged carbocation. Acetic acid is the solvent of choice when reducing an aryl nitro-group to aniline using palladium-on-carbon.

Glacial acetic acid is used in analytical chemistry for the estimation of weakly alkaline substances such as organic amides. Glacial acetic acid is a much weaker base than water, so the amide behaves as a strong base in this medium. It then can be titrated using a solution in glacial acetic acid of a very strong acid, such as perchloric acid.

Dilute solutions of acetic acids are also used as a stop bath during the development of photographic films, and in descaling agents to remove limescale from taps and kettles. In the clinical laboratory dilute acetic acid lyse red blood cells in order to facilitate microscopic examination.

Acetic acid in the form of household vinegar is often used to clean indoor climbing holds of chalk.

The acidity is also used for treating the sting of the box jellyfish by disabling the stinging cells of the jellyfish, preventing serious injury or death if applied immediately, and for treating outer ear infections in people in preparations such as Vosol. In this manner, acetic acid is used as a spray-on preservative for livestock silage, to discourage bacterial and fungal growth. Glacial acetic acid is also used as a wart and verruca remover.

Safety
Concentrated acetic acid is corrosive to skin and must, therefore, be handled with appropriate care, since it can cause skin burns, permanent eye damage, and irritation to the mucous membranes. These burns or blisters may not appear until hours after exposure. Latex gloves offer no protection, so specially resistant gloves, such as those made of nitrile rubber, are worn when handling the compound. Concentrated acetic acid can be ignited with difficulty in the laboratory. It becomes a flammable risk if the ambient temperature exceeds 39 °C (102 °F), and can form explosive mixtures with air above this temperature (explosive limits: 5.4–16%).
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