Description
Acetic acid is the simplest
carboxylic acid next to formic acid in which a single hydrogen atom
is attached to the carboxyl group. If a methyl group is attached to
the carboxyl group, the compound is acetic acid. Acetic acid is a
clear, corrosive, flammable liquid; melting point *6.6 C, boiling
point **8 C. Pure acetic acid freezes in ice-like crystal form. So
pure acetic acid is called glacial acetic acid, which contains *9.5
***0.5 % w/w. It is the two-carbon carboxylic acid, and a
systematic name is ethanoic acid. It is completely miscible with
water, ethyl alcohol and ether, but is insoluble in carbon
disulfide. It is a characteristic component of vinegar and an
important biochemical intermediate in the form of acetylcoenzyme A,
mostly. Most commercial production of virgin synthetic acetic acid
is based on methanol carbonylation. Significant volumes of
acetic acid are recovered in cellulose acetate operations and
lesser quantities during production of polyvinyl alcohol and
butyral, peracetic acid, ethylene-vinyl alcohol and acetaminophen
and aspirin. Capacity utilization is likely to remain high for the
next few years because of good demand for purified terephthalic
acid and vinyl acetate monomer.
Vinyl acetate monomer
The largest consumption of acetic
acid is as a raw material to produce vinyl acetate by reaction with
ethylene and oxygen or with acetylene in the presence of
palladium catalyst. Vinyl acetate is polymerized to polyvinyl
acetate by itself and to other copolymers with other monomers.
Acetate polymers are important resins used in paints, adhesives,
plastics and textile finishes.
Acetic anhydride
The next largest consumption of
acetic acid is to produce acetic anhydride by condensation reaction
of two acetic acid molecules. This chemical is principally used in
the manufacture of cellulose acetate having the application as a
base for magnetic tape and in the manufacture of textile fibres.
Also, it is heated with salicylic acid to produce acetylsalicylic
acid (aspirin). It is also used in the manufacture of pigments,
dyes, cellulose and pesticides etc.
Solvent
Acetic acid is used as a solvent
in the production of terephthalic acid from p-xylene. Terephthalic
acid is the raw material for polyester fiber. Terephthalic acid has
become a more important raw material for non-fiber field,
PET-bottle, PET-film and engineering plastics and as poultry feed
additives.
Esters
Considerable quantities of acetic
acid are used to manufacture esters such as ethyl and butyl
acetate. Acetate esters demonstrate good solvency for many natural
and synthetic resins. They are general purpose solvents which are
applied commonly in lacquer thinners, wood lacquers and a wide
variety of coatings, plasticizer and pharmaceutical
fields.
Chloroacetic acid
The stronger acid (chloroacetic
acid) is manufactured from acetic acid by reaction with chlorine.
Chloroacetic acid reacts with alkali cellulose to produce
carboxymethylcellulose (CMC). Chloroacetic acid is the parent
material for the production of a series of phenoxy herbicides such
as 2,*-dichlorophenoxyacetic acid and 2,4,*-trichlorophenoxyacetic
acid.
Acetic acid is used as
an acidulant in a wide range of applications from eletroplating to
textiles finishing operation. It is used in the manufacture of
materials used in the pharmaceuticals, foods, cosmetics and
colorant chemical fields including sorbic acid, dyestuffs and
pigments, vitamins, antibiotics, rubber chemicals and flavor &
fragrance.
