acetic acid(redirected from Methanecarboxylic acid)
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acetic acid(əsē`tĭk), CH3CO2H, colorless liquid that has a characteristic pungent odor, boils at 118°C;, and is miscible with water in all proportions; it is a weak organic carboxylic acid (see carboxyl groupcarboxyl group
, in chemistry, functional group that consists of a carbon atom joined to an oxygen atom by a double bond and to a hydroxyl group, OH, by a single bond. Carboxylic acids are compounds whose molecules contain a carboxyl group that is joined to a hydrogen atom, an
..... Click the link for more information. ). Glacial acetic acid is concentrated, 99.5% pure acetic acid; it solidifies at about 17°C; to a crystalline mass resembling ice. Acetic acid is the major acid in vinegarvinegar,
sour liquid consisting mainly of acetic acid and water, produced by the action of bacteria on dilute solutions of ethyl alcohol derived from previous yeast fermentation.
..... Click the link for more information. ; as such, it is widely used as a food preservative and condiment. For industrial use concentrated acetic acid is prepared from the oxidation of acetaldehydeacetaldehyde
, CH3CHO, colorless liquid aldehyde, sometimes simply called aldehyde. It melts at −123°C;, boils at 20.8°C;, and is soluble in water and ethanol.
..... Click the link for more information. . Acetic acid is also a product in the destructive distillation of wood. It reacts with other chemicals to form numerous compounds of commercial importance. These include cellulose acetate, used in making acetate rayon, nonflammable motion-picture film, lacquers, and plastics; various inorganic salts, e.g., lead, potassium, and copper acetates; and amyl, butyl, ethyl, methyl, and propyl acetatesacetate
, one of the most important forms of artificial cellulose-based fibers; the ester of acetic acid. The first patents for the production of fibers from cellulose acetate appeared at the beginning of the 20th cent.
..... Click the link for more information. , which are used as solvents, chiefly in certain quick-drying lacquers and cements. Amyl acetate is sometimes called banana oil because it has a characteristic banana odor.
CH3COOH, a monobasic carboxylic acid of the aliphatic series. Acetic acid is a colorless liquid with a pungent odor and an acid taste. Anhydrous, or glacial, acetic acid has a melting point of 16.75°C, a boiling point of 118.1°C, and a density of 1.055 g/cm3 at 15°C. Acetic acid is miscible with water, alcohol, ether, benzene, and many other organic solvents. It is not soluble in carbon disulfide, but it readily dissolves many inorganic and organic substances, including sulfur, phosphorus, hydrogen halides, and cellulose acetate. Acetic acid is a weak acid, with a dissociation constant K = 1.75 × 10–5. It forms such typical derivatives of carboxylic acids as salts and esters, called acetates, an anhydride, an acid halide, amides, and anilides.
Acetic acid, in the form of vinegar, was the first acid known to man. It is widespread in nature both in free form and in the form of salts and esters, and it is formed during putrefaction and fermentation. There are four main industrial methods of preparing acetic acid: (1) oxidation of acetaldehyde by exposure to air or oxygen at 60°C in the presence of manganese acetate [(CH3COO)2Mn]; (2) pyrolysis of acetone with subsequent hydration of the resulting ketene
(3) oxidation of individual hydrocarbons, such as butane or benzine fractions; and (4) reaction of methanol with carbon monoxide. Another method, still of some importance, is the extraction of acetic acid from wood vinegar, one of the products obtained from the dry distillation of wood. The acetic acid in vinegar is obtained by the acetic fermentation of alcoholic liquids.
In industry, acetic acid, together with acetic anhydride and acetyl chloride, is used for introducing the acetyl radical (CH3CO—)—a process known as acetylation—in, for example, the preparation of the esters used as perfumes, solvents, and pharmaceuticals (acetylsalicylic acid, phenacetin). Salts of acetic acid are used in the preparation of pigments (acetates of lead and copper); other salts are used as catalysts (acetates of manganese, cobalt, zinc), and as mordants in dyeing (basic salts of acetic acid).
Acetic acid vapors irritate the mucosa and, in particular, the eyes; the permissible concentration of the vapors in the air is 0.005 milligram per liter. Concentrated (more than 30 percent) solutions of acetic acid cause burns upon contact with the skin.
V. N. FROSIN