Phthalic acid

chemical compound

In a field of chemistry called "Organic Chemistry", which mainly involves the study of carbon-based molecules, phthalic acid, is a dicarboxylic acid, which refers to the two COOH groups present in the molecule. The two carboxylic acids are present on an aromatic ring, here benzene, which is where the systematic name "Benzene-1,2-dicarboxylic acid" is from.

Phthalic acid
Phthalic acids
Ball-and-stick model of the phthalic acid molecule
Names
Preferred IUPAC name
Benzene-1,2-dicarboxylic acid
Other names
1,2-Benzenedioic acid
Phthalic acid
Benzene-1,2-dioic acid
ortho-Phthalic acid
Dicarboxylbenzene
Carboxylbenzoic acid
1,2-Phenylenedicarboxylic acid
Phenylene-1,2-dicarboxylic acid
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.001.703
EC Number
  • 201-873-2
UNII
  • OC(=O)c1ccccc1C(=O)O
Properties
C
8
H
6
O
4
Molar mass 166.132 g/mol
Appearance white solid
Density 1.593 g/cm3, solid
Melting point 207 °C (405 °F; 480 K)[3]
0.6 g / 100 mL [1]
Acidity (pKa) 2.89, 5.51[2]
-83.61·10−6 cm3/mol
Hazards
NFPA 704

0
2
0
 
Related compounds
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Phthalic acid is one of three structural isomers of benzenedicarboxylic acid. Which refers to the placement of the two carboxylic acids on the benzene-ring. If there were a gap between them it would be the molecule isophthalic acid, with the systematic name Benzene-1,3-dicarboxylic acid, while if the acid groups were opposing each other, it would be terephthalic acid, with the systematic name Benzene-1,4-dicarboxylic acid.

Synthesis

change

The molecule "Napthalene", when oxidised by potassium permanganate, or similarly strong oxidizers,[4] gives the molecule Phthalic anhydride, with through hydrolysis with hot water, gives Phthalic acid.[5]

References

change
  1. "PHTHALIC ACID". hazard.com.
  2. 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.
  3. Several melting points are reported, for example: (i) 480. K (NIST website), (ii) 210−211 °C with decomposition (Sigma-Aldrich on-line), (iii) 191 °C in a sealed tube (Ullmann's Encyclopedia of Industrial Chemistry), (iv) 230 °C with conversion to phthalic anhydride and water (J.T.Baker MSDS).
  4. "Oxidation of Naphthalene to Phthalic Anhydride". public.websites.umich.edu. Retrieved 2024-06-15.
  5. Noller, Carl R. (1965). Chemistry of Organic Compounds (3rd ed.). Philadelphia: W. B. Saunders. p. 602.