Phthalic acid

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Phthalic acid
Phthalic acid
Phthalic-acid-3D-balls.png
Identifiers
CAS number 88-99-3 YesY
PubChem 1017
ChemSpider 992
EC number 201-873-2
ChEBI CHEBI:29069
Jmol-3D images Image 1
Properties
Molecular formula C8H6O4
Molar mass 166.14 g/mol
Appearance white solid
Density 1.593 g/cm3, solid
Melting point 191−230 °C[1]
Solubility in water 0.6 g / 100 mL [2][3]
Acidity (pKa) 2.89, 5.51[4]
Hazards
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Related compounds
Related carboxylic acids Isophthalic acid
Terephthalic acid
Related compounds Phthalic anhydride
Phthalimide
Phthalhydrazide
Phthaloyl chloride
Benzene-1,2-
dicarboxaldehyde
Except where noted otherwise, 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 an aromatic dicarboxylic acid, with formula C6H4(CO2H)2. It is an isomer of isophthalic acid and terephthalic acid. Although phthalic acid is of modest commercial importance, the closely related derivative phthalic anhydride is a commodity chemical produced on a large scale.[5]

Production[edit]

Phthalic acid is produced by the catalytic oxidation of naphthalene directly to phthalic anhydride and a subsequent hydrolysis of the anhydride.[5]

Phthalic acid was first obtained by French chemist Auguste Laurent in 1836 by oxidizing naphthalene tetrachloride. Believing the resulting substance to be a naphthalene derivative, he named it "naphthalic acid".[6] After the Swiss chemist Jean Charles Galissard de Marignac determined its correct formula,[7] Laurent gave it its present name.[8] Manufacturing methods in the nineteenth century included oxidation of naphthalene tetrachloride with nitric acid, or, better, oxidation of the hydrocarbon with fuming sulfuric acid, using mercury or mercury(II) sulfate as a catalyst.

Reactions and uses[edit]

Phthalic acid crystals

It is a dibasic acid, with pKa's of 2.89 and 5.51. The monopotassium salt, potassium hydrogen phthalate is a standard acid in analytical chemistry. Typically phthalate esters are prepared from the widely available phthalic anhydride. Reduction of phthalic acid with sodium amalgam in the presence of water gives the 1,3-cyclohexadiene derivative.[9]

Isomers[edit]

Phthalic acid is one of three isomers of benzenedicarboxylic acid, the others being isophthalic acid and terephthalic acid. Sometimes the term "phthalic acids" is used to refer to this family of isomers, but in the singular, "phthalic acid", refers exclusively to the ortho- isomer.

Phthalic-acid-2D-skeletal.png Isophthalic-acid-2D-skeletal.png Terephthalic-acid-2D-skeletal.png
  phthalic acid     isophthalic acid     terephthalic acid
  (ortho-phthalic acid)     (meta-phthalic acid)     (para-phthalic acid)

Safety[edit]

The toxicity of phthalic acid is low with LD50 (mouse) of 550 mg/kg. However, many phthalate esters have been implicated as endocrine disruptors.

Biodegradation[edit]

The bacteria Pseudomonas sp. P1 degrades phthalic acid. [10]

See also[edit]

References[edit]

  1. ^ Several melting points are reported, for example: (i) 210−211 °C with decomposition (Sigma-Aldrich on-line), (ii) 191 °C in a sealed tube (Ullmann's Encyclopedia of Industrial Chemistry), (iii) 230 °C with conversion to phthalic anhydride and water (J.T.Baker MSDS).
  2. ^ http://hazard.com/msds/mf/baker/baker/files/p4270.htm
  3. ^ http://actrav.itcilo.org/actrav-english/telearn/osh/ic/88993.htm
  4. ^ 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.
  5. ^ a b Peter M. Lorz, Friedrich K. Towae, Walter Enke, Rudolf Jäckh, Naresh Bhargava, Wolfgang Hillesheim “Phthalic Acid and Derivatives” in Ullmann's Encyclopedia of Industrial Chemistry, 2007, Wiley-VCH, Weinheim. doi:10.1002/14356007.a20_181.pub2
  6. ^ See:
    • Auguste Laurent (1836) "Sur l'acide naphtalique et ses combinaisons" (On naphthalic acid and its compounds), Annales de Chimie et de Physique, 61 : 113-125. (Note: The empirical formulae of the compounds that were analyzed in this article are incorrect, in part because, during this period, chemists used incorrect atomic masses for carbon (6 instead of 12) and other elements.)
    • Reprinted in German as: Auguste Laurent (1836) "Ueber Naphthalinsäure und ihre Verbindungen" (On naphthalenic acid and its compounds), Annalen der Pharmacie, 19 (1) : 38-50; for the preparation of phthalic acid, see page 41.
  7. ^ C. de Marignac (1841) "Ueber die Naphtalinsäure und ein bei ihrer Darstellung entstehendes flüchtiges Produkt" (On naphthalinic acid and a volitile product that arises during its preparation), Annalen der Chemie und Pharmacie, 38 (1) : 13-20. (Note: Again, Marignac's empirical formulae are wrong because chemists at this time used incorrect atomic masses.)
  8. ^ See:
  9. ^ Richard N. McDonald and Charles E. Reineke (1988), "trans-1,2-Dihydrophthalic Acid", Org. Synth. ; Coll. Vol. 6: 461 
  10. ^ Ishtiaq Ali, Muhammad (2011). Microbial degradation of polyvinyl chloride plastics (Ph.D.). Quaid-i-Azam University. p. 47. 
  • Merck Index, 9th ed, #7178

External links[edit]

Public Domain This article incorporates text from a publication now in the public domainChisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press.