Acetic acid is one of the simplest carboxylic acids. Dilute acetic acid is also called as vinegar which is used
in food preparation to get sour taste.
Acetic acid is the precursor for many industrial chemicals. It is mainly used in the production of cellulose acetate mainly for
photographic film and polyvinyl acetate for wood glue, as well as synthetic fibers and fabrics.
The Monsanto acetic acid process is the chief commercial method for production of acetic acid.
Manufacture of Acetic acid:
From ethanol:
The oxidation of fermented liquor(containing 10% to 15% alcohol) under the influence of acetobactor produces acetic acid.
When a solution of 3% to 7% of acid is obtained, then the solution is commonly called vinegar.
From methanol:
The other commercial method for the manufacture of acetic acid is addition of methyl alcohol over carbon monoxide. In this
method, methanol vapors and carbon monoxide are made to react in the presence of catalyst Iodine – Rhodium.
Action with metallic carbonates and hydrogen carbonates
Physical properties of acetic acid:
Pure acetic acid is a corrosive and colorless liquid. It has a pungent smell of its own, like that of vinegar and has a sour
taste. It freezes below 16.5°C to form icy (glacier) mass, called glacial acetic acid. Boiling point is 118°C(391 K) and
its density is 1.08 g cm−3 at room temperature. Since it is a polar compound it is soluble in water in all
proportions.
Chemical properties of Acetic acid:
- Acetic acid ionizes in water to the extent of 4% to produce H+ ions.
- Acetic acid reacts with metallic carbonates or hydrogen carbonates with lot of effervescence, with the formation of metallic ethanoates, water and carbon dioxide gas.
Action with alkalis
Decarboxylation of Acetic acid
- Acetic acids reacts with alkalis and form their respective salts and water.
- The process of removal of – COOH group from an alkanoic acid is called decarboxylation.
- The decarboxylation of acetic acid is carried by soda lime which is a mixture of NaOH and quicklime (CaO), gives methane.
Use of vinegar as a preservative
Uses:
- Vinegar is used for preserving food articles.
- Acetic acid is used in the manufacture of cellulose acetate, which is used for making synthetic fibers.
- It is used in the manufacture of acetone and esters, which are used in perfumes, dyes, drugs and pharmaceutical industries.
- It is used in preparation of lead acetate, which is used in paints.
- Aluminum acetate and chromium acetate are used as mordants in dying industry.
- It is used in coagulating rubber from latex and casein from milk.