Isophthalic acid

Isophthalic acid
	Skeletal formula
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. It is a white solid that is very poorly soluble in water (0.012 g/100 mL at room temperature). The main industrial uses of purified isophthalic acid (PIA) are as a comonomer in the production of polyethylene terephthalate (PET) resin and for the production of unsaturated polyester resin (UPR) and other types of coating resins..^[2]

Structure

Isophthalic acid is one of three isomeric benzenedicarboxylic acid]]s, the others are phthalic acid and terephthalic acid. Crystalline isophthalic acid is built up from molecules connected by hydrogen bonds, forming infinite chains.^[3]

Preparation

Isophthalic acid is produced by oxidizing meta-xylene using oxygen:

C₆H₄(CH₃)₂ + 3O₂ → C₆H₄(CO₂H)₂ + 2 H₂O

The approach is comparable to some routes to terephthalic acid.^[2]

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.

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.
^ ^a ^b Tomás, Rogério A.F.; Bordado, João C.M.; Gomes, João F.P.; Sheehan, Richard J. (2024). "Terephthalic Acid, Dimethyl Terephthalate, and Isophthalic Acid". Ullmann's Encyclopedia of Industrial Chemistry. pp. 1–17. doi:10.1002/14356007.a26_193.pub3. ISBN 978-3-527-30385-4.
^ Derissen, JL (1974). "The crystal structure of isophthalic acid". Acta Crystallogr. B30 (6): 764–2765. doi:10.1107/S0567740872004844.

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.

[Ull-2] Tomás, Rogério A.F.; Bordado, João C.M.; Gomes, João F.P.; Sheehan, Richard J. (2024). "Terephthalic Acid, Dimethyl Terephthalate, and Isophthalic Acid". Ullmann's Encyclopedia of Industrial Chemistry. pp. 1–17. doi:10.1002/14356007.a26_193.pub3. ISBN 978-3-527-30385-4.

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

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