Issues+of+Acetic+Acid

=Introduction=

Acetic acid, CH3COOH, also known as ethanoic acid, is an organic acid that gives vinegar its sour taste and pungent smell. It is a weak acid, in that it is only a partially dissociated acid in an a. aqueous solution Pure, water-free acetic acid (glacial acetic acid) is a colourless liquid that absorbs water from the environment (hygroscopy), and freezes at 16.5 o C (62 o F) to a colourless crystalline solid. The pure acid and its concentrated solutions are very corrosive.

Acetic acid is one of the simplest carboxylic acids. It is an important chemical reagent and industrial chemical, used in the production o polyethylene terephthalate mainly used in soft drink bottles; celullose ace, mainly for photograpich and polyvhinyl acetate for wood glue, as well as synthetic fibres and fabrics. In households, diluted acetic acid is often used in descaling agent. In the food industry, acetic acid is used under the food aditive code E260 as an acidity regulator and as a condiment. The global demand of acetic acid is around 6.5 million tonnes per year (Mt/a), of which approximately 1.5 Mt/a is met by recycling; the remainder is manufactured from petrochemical feedstocks or from biological sources. Dilute acetic acid produced by natural fermentation is called vinegar.

= Applications =

__2.5-litre bottle of acetic acid in a laboratory. The bottle is made out of amber glass.__ 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 followed by acetic anhydride and ester production. The volume of acetic acid used in vinegar is comparatively small.

Vinyl acetate monomer
The major use of acetic acid is for the production of vinyl acetate monomer (VAM). This application consumes approximately 40% to 45% of the world's production of acetic acid. The reaction is of ethylene and acetic acid with oxygen over a palladium catalyst. 2 H 3 C-COOH + 2 C 2 H 4 + O2 → 2 H 3 C-CO-O-CH=CH 2 + 2 H 2 O Vinyl acetate can be polymerized to polyvhinyl acetate or to other polymers, which are applied in paints and adhesives.

Ester production
The major esters of acetic acid are commonly used solvents for links, paints and coating. The esters include ethyl acetate, n-butyl acetate, isobutyl acetate, and propyl acetate. They are typically produced by catalysed reaction from acetic acid and the corresponding alcohol: H 3 C-COOH + HO-R → H 3 C-CO-O-R + H 2 O, (R = a general alkyl group) Most acetate esters, however, are produced from acetaldehyde using the tishcenko reaction. In addition, ether acetates are used as solvents for nitrocellulose, acrylic laqued, varnis removers, and wood stains. First, glycol monoethers are produced from ethilene oxide or propylene oxide with alcohol, which are then esterified with acetic acid. The three major products are ethylene glycol monoethyl ether acetate (EEA), ethylene glycol monobutyl ether acetate (EBA), and propylene glycol monomethyl ether acetate (PMA, more commonly known as PGMEA in semiconductor manufacturing processes, where it is used as a resist solvent). This application consumes about 15% to 20% of worldwide acetic acid. Ether acetates, for example EEA, have been shown to be harmful to human reproduction.

Acetic anhydride
The condensation product of two molecules of acetic acid is acetic anhydride. The worldwide production of acetic anhydride is a major application, and uses approximately 25% to 30% of the global production of acetic acid. Acetic anhydride may be produced directly by metanol anhydride by passing the acid, and cative production plants can be adapted for anhydride production. Acetic anhydride is a strong acetalytion agent. As such, its major application is for celulose acetate, a synthetic textille also used for photograpich film. Acetic anhydride is also a reagent for the production of aspirin, heroin, and other compounds.

Vinegar
In the form of vinegar, acetic acid solutions (typically 4% to 18% acetic acid, with the percentage usually calculated by mass) are used directly as a condiment, and also in the pickling of vegetables and other foods. Table vinegar tends to be more diluted (4% to 8% acetic acid), while commercial food pickling, in general, employs more concentrated solutions. The amount of acetic acid used as vinegar on a worldwide scale is not large, but is by far the oldest and best-known application.

Use as solvent
Glacial acetic acid is an excellent polar protic solvent, as noted above. It is frequently used as a solvent for recritalization to purify organic compounds. Pure acetic acid is used as a solvent in the production of terephtalic (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 carbocation, such as Friedel-Crafts alkylation. For example, one stage in the commercial manufacture of synthetic champor involvea a Wagner-Meerwein raerrangement of camphene to isobornyl acetate; here acetic acid acts both as a solvent and as a nucleophille 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.

Other applications
Dilute solutions of acetic acids are also used for their mild acidity. Examples in the household environment include the use in a stop bath during the development of photographic films, and in descaling agents to remove limescale from taps and kettles. Dilute solutions of glacial acetic acid can be used in the clinical laboratory to lyse red blood cell in order to do manual white blood cell counts. Another clinical use is for lysing red blood cells, which can obscure other important constituents in urine during a microscopic examination. The acidity is also used for treating the sting of the box jelly fish 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. Organic or inorganic salts are produced from acetic acid, including: Substituted acetic acids produced include: Amounts of acetic acid used in these other applications together (apart from TPA) account for another 5–10% of acetic acid use worldwide. These applications are, however, not expected to grow as much as TPA production.Diluted acetic acid is also used in physical therapy to break up nodules of scar tissue via iontophoresis.
 * Sodium acetate, used in the textile industry and as a food preservative.
 * Copper (II) acetate, used as a pigment and a fungicide.
 * Aluminium acetate and iron (II) acetate—used as mordants for dyes.
 * Palladium (II) acetate, used as a catalyst for organic coupling reactions such as the heck reaction.
 * Silver acetate, used as a pesticide.
 * Monochloroacetic acid (MCA), dichloroacetic acid (considered a by-product), and trichloroacetic acid. MCA is used in the manufacture of indigo dyes.
 * Bromoacetic acid, which to produce the reagent ethyl bromoacetate.
 * Trifluoroacetic acid, which is a common reagent in organic synthesis.