Isophthalic acid is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...

C₆H₄(CO₂H)₂. This colorless solid is an isomer of

phthalic acid Phthalic acid is an aromatic dicarboxylic acid, with formula C6H4(CO2H)2. Although phthalic acid is of modest commercial importance, the closely related derivative phthalic anhydride is a commodity chemical produced on a large scale. Phthalic aci ...

and terephthalic acid. The main industrial uses of purified isophthalic acid (PIA) are for the production of

polyethylene terephthalate Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods ...

(PET) resin and for the production of

unsaturated polyester resin Polyester resins are synthetic resins formed by the reaction of dibasic organic acids and polyhydric alcohols. Maleic anhydride is a commonly used raw material with diacid functionality in unsaturated polyester resins. Unsaturated polyester resins ...

(UPR) and other types of coating resins. Isophthalic acid is one of three

isomers In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. ...

of benzenedicarboxylic acid, the others being

and terephthalic acid.

Preparation

Isophthalic acid is produced on the billion kilogram per year scale by oxidizing meta-xylene using oxygen. The process employs a

cobalt Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

. The world's largest producer of isophthalic acid is Lotte Chemical Corporation. In the laboratory,

chromic acid The term chromic acid is usually used for a mixture made by adding concentrated sulfuric acid to a dichromate, which may contain a variety of compounds, including solid chromium trioxide. This kind of chromic acid may be used as a cleaning mixtu ...

can be used as the oxidant. It also arises by fusing potassium meta-sulfobenzoate, or meta-bromobenzoate with potassium formate (terephthalic acid is also formed in the last case). The barium

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...

, as its

hexahydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

, is very soluble in water (a distinction between phthalic and terephthalic acids).

Uvitic acid Uvitic acid (5-methylisophthalic acid) is an organic compound with the formula CH3C6H3(COOH)2. The name comes from Latin ''uva'' which means a grape. The acid is called so because it may be produced indirectly from tartaric acid, which is found in ...

, 5-methylisophthalic acid, is obtained by oxidizing

mesitylene Mesitylene or 1,3,5-trimethylbenzene is a derivative of benzene with three methyl substituents positioned symmetrically around the ring. The other two isomeric trimethylbenzenes are 1,2,4-trimethylbenzene (pseudocumene) and 1,2,3-trimethylbenze ...

or by condensing pyroracemic acid with baryta water.

Applications

Aromatic In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...

dicarboxylic acid In organic chemistry, a dicarboxylic acid is an organic compound containing two carboxyl groups (). The general molecular formula for dicarboxylic acids can be written as , where R can be aliphatic or aromatic. In general, dicarboxylic acids show ...

s are used as precursors (in form of

acyl chloride In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group . Their formula is usually written , where R is a side chain. They are reactive derivatives of carboxylic acids (). A specific example o ...

s) to commercially important polymers, e.g. the fire-resistant material

Nomex Nomex is a flame-resistant meta-aramid material developed in the early 1960s by DuPont and first marketed in 1967. Properties Nomex and related aramid polymers are related to nylon, but have aromatic backbones, and hence are more rigid and mo ...

. Mixed with terephthalic acid, isophthalic acid is used in the production of PET resins for drink

plastic bottle A plastic bottle is a bottle constructed from high-density or low density plastic. Plastic bottles are typically used to store liquids such as water, soft drinks, motor oil, cooking oil, medicine, shampoo, milk, and ink. The size ranges from v ...

s and food packaging. The high-performance polymer

polybenzimidazole Polybenzimidazole (PBI, short for poly ,2’-(''m''-phenylen)-5,5’-bisbenzimidazole'') fiber is a synthetic fiber with a very high decomposition temperature. It does not exhibit a melting point, it has exceptional thermal and chemical stability ...

is produced from isophthalic acid. Also, the acid is used as an important input to produce insulation materials.

References

Note: reference 2 refers to the ortho isomer. Accurate cites for the meta isomer not available.

External links

International Chemical Safety Card 0500
{{Authority control Dicarboxylic acids Monomers Benzoic acids