Isophthalic acid

Isophthalic acid
Names
	Preferred IUPAC name Benzene-1,3-dicarboxylic acid
	Other names Isophthalic acid; meta-Phthalic acid
Identifiers
CAS Number	121-91-5 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:30802 ;
ChemSpider	8182 ;
ECHA InfoCard	100.004.098
PubChem CID	8496;
UNII	X35216H9FJ ;
CompTox Dashboard (EPA)	DTXSID3021485 ;
	InChI InChI=1S/C8H6O4/c9-7(10)5-2-1-3-6(4-5)8(11)12/h1-4H,(H,9,10)(H,11,12) Key: QQVIHTHCMHWDBS-UHFFFAOYSA-N ; InChI=1/C8H6O4/c9-7(10)5-2-1-3-6(4-5)8(11)12/h1-4H,(H,9,10)(H,11,12) Key: QQVIHTHCMHWDBS-UHFFFAOYAY;
	SMILES O=C(O)c1cccc(C(=O)O)c1;
Properties
Chemical formula	C8H6O4
Molar mass	166.132 g·mol−1
Appearance	White crystalline solid
Density	1.526 g/cm3, Solid
Solubility in water	Insoluble
Acidity (pKa)	3.46, 4.46
Magnetic susceptibility (χ)	-84.64·10−6 cm3/mol
Related compounds
Related carboxylic acids	Benzoic acid; Phthalic acid (ortho) ; Terephthalic acid (para) ; Trimesic acid
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Isophthalic acid is an organic compound with the formula C₆H₄(CO₂H)₂. This colorless solid is an isomer of phthalic acid and terephthalic acid. The main industrial uses of purified isophthalic acid (PIA) are for the production of polyethylene terephthalate (PET) resin and for the production of unsaturated polyester resin (UPR) and other types of coating resins.

Isophthalic acid is one of three isomers of benzenedicarboxylic acid, the others being phthalic acid and terephthalic acid.

Crystalline isophthalic acid is built up from molecules connected by hydrogen bonds, forming infinite chains.^[2]

Preparation

Isophthalic acid is produced on the billion kilogram per year scale by oxidizing meta-xylene using oxygen.^[3] The process employs a cobalt-manganese catalyst. The world's largest producer of isophthalic acid is Lotte Chemical Corporation.^[4]

In the laboratory, chromic acid 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, as its hexahydrate, is very soluble in water (a distinction between phthalic and terephthalic acids). Uvitic acid, 5-methylisophthalic acid, is obtained by oxidizing mesitylene or by condensing pyroracemic acid with baryta water.

Applications

Aromatic dicarboxylic acids are used as precursors (in the form of acyl chlorides) to commercially important polymers, e.g. the fire-resistant material Nomex. Mixed with terephthalic acid, isophthalic acid is used in the production of PET resins for drink plastic bottles and food packaging. The high-performance polymer polybenzimidazole is produced from isophthalic acid.^[3] Also, the acid is used as an important input to produce insulation materials.

References

^ Brown, H.C., et al., in Baude, E.A. and Nachod, F.C., Determination of Organic Structures by Physical Methods, Academic Press, New York, 1955.
^ Derissen, JL (1974). "The crystal structure of isophthalic acid". Acta Crystallogr. B30 (6): 764–2765. doi:10.1107/S0567740872004844.
^ ^a ^b Lorz, Peter M.; Towae, Friedrich K.; Enke, Walter; Jäckh, Rudolf; Bhargava, Naresh; Hillesheim, Wolfgang (2007). "Phthalic Acid and Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a20_181.pub2. ISBN 978-3527306732.
^ "Lotte Chemical to invest $3.2mn to beef up meta-xylene and polycarbonate production". Pulse.

[[#ref_{{{1}}}|^]] Note: reference 2 refers to the ortho isomer. Accurate cites for the meta isomer not available.

External links

International Chemical Safety Card 0500

[1] Brown, H.C., et al., in Baude, E.A. and Nachod, F.C., Determination of Organic Structures by Physical Methods, Academic Press, New York, 1955.

[2] Derissen, JL (1974). "The crystal structure of isophthalic acid". Acta Crystallogr. B30 (6): 764–2765. doi:10.1107/S0567740872004844.

[Ullmann-3] Lorz, Peter M.; Towae, Friedrich K.; Enke, Walter; Jäckh, Rudolf; Bhargava, Naresh; Hillesheim, Wolfgang (2007). "Phthalic Acid and Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a20_181.pub2. ISBN 978-3527306732.

[4] "Lotte Chemical to invest $3.2mn to beef up meta-xylene and polycarbonate production". Pulse.

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