Acetic acid  is a colorless, pungent, water-miscible liquid, C 2  H 4  O 2  , the essential constituent of vinegar, produced by oxidation of acetaldehyde, bacterial action on ethyl alcohol, the reaction of methyl alcohol with carbon monoxide, and other processes: used chiefly in the manufacture of acetate fibers and in the production of numerous esters that are solvents and flavoring agents.
Acetic acid(CAS.NO:64-19-7) is the acid most commonly associated with vinegar. Acetic acid is a two-carbon carboxylic acid. It is the most commercially important organic acid and is used in the manufacture of a broad range of chemical products, such as plastics and insecticides.
1. Used in Food

This clear, colorless acid has a distinctive sour taste, although tasting it is not recommended unless it is clearly labeled as fit for human consumption. It also has a strong, sharp odor which is familiar to many people because it smells like vinegar. Or, rather, vinegar smells like acetic acid. In food preparation, it can be used as a flavoring, with the sharp taste being desirable in some foods, and also as a food preservative. The acid inhibits bacterial growth, keeping food safe from contamination. The historic use of vinegar as a food preservative has created an acquired taste in some cultures for the distinctive tang of vinegar, so foods which no longer require preservation may have some added vinegar for flavor.
2. Industrially Use
Industrially, acetic acid is used in a wide range of processes. It is also used in chemical production and research, in settings where people have need for a weak acid. Like other acids, acetic acid is corrosive for many substances, and it can be involved in a variety of chemical reactions. Acetic acid is used as a solvent, a reagent, a catalyst, and a pesticide. It can be used in the preparation of paints, varnishes, and glazes, and in medical treatment, as for example in the treatment of jellyfish stings.
Most important carboxylic acid (CHCOOH). Pure (“glacial”) acetic acid is a clear, syrupy, corrosive liquid that mixes readily with water. Vinegar is its dilute solution, from fermentation and oxidation (see oxidation-reduction) of natural products. Its salts and esters are acetates. It occurs naturally as a metabolic intermediate in body fluids and plant juices. Industrial production is either synthetic, from acetylene, or biological, from ethanol. Industrial chemicals made from it are used in printing and as plastics, photographic films, textiles, and solvents.
3. Medical Use

Acetic acid is used to treat an outer ear infection (external otitis). It works by stopping the growth of bacteria and fungus. Treating the infection reduces pain and swelling in the ear. Wetness in the ear canal can help bacteria and fungus to grow. This medication may also contain drying ingredients such as glycerin or alcohol. Drying of the ear canal helps to cure the infection.
4. 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 was 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.
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.