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Phthalic acid



Phthalic acid
Other names Benzene-1,2-
dicarboxylic acid
Identifiers
CAS number 88-99-3
EINECS number 201-873-2
SMILES C1=CC=C(C(=C1)
C(=O)O)C(=O)O
Properties
Molecular formula C6H4(COOH)2
Molar mass 166.14 g/mol
Appearance white solid
Density 1.593 g/cm3, solid
Melting point

210 °C decomp.

Solubility in water Slightly soluble
Hazards
EU classification not listed
NFPA 704
1
 
1
 
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, 100 kPa)

Infobox disclaimer and references

Phthalic acid (IUPAC systematic name: benzene-1,2-dicarboxylic acid) is an aromatic dicarboxylic acid, with formula C6H4(COOH)2. It is an isomer of isophthalic acid and terephthalic acid.

Additional recommended knowledge

Contents

Uses

Phthalic acid is used mainly in the form of the anhydride to produce other chemicals such as dyes, perfumes, saccharin, phthalates and many others.

History

Phthalic acid was obtained by French chemist Auguste Laurent in 1836 by oxidizing naphthalene tetrachloride, and, believing the resulting substance to be a naphthalene derivative, he named it naphthalenic acid. Swiss chemist Jean Charles Galissard de Marignac determined its formula and showed Laurent’s supposition to be incorrect, upon which Laurent gave it its present name. Manufacturing methods in the nineteenth century included oxidation of naphthalene tetrachloride (prepared from naphthalene, potassium chlorate and hydrochloric acid) with nitric acid, or, better, oxidation of the hydrocarbon with fuming sulfuric acid, using mercury or mercury(II) sulfate as a catalyst.

The catalytic oxidation of naphtalene directly to phthalic anhydride and a subsequent hydrolysis of the anhydride is one of the new production methods.

Chemistry

It forms white crystals, melting at 210 °C with decomposition into water and phthalic anhydride. Heating with an excess of lime produces benzene. The acid (and anhydride) are largely used in the color industry (see phenolphthalein).

See also

References

None.

    This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.

     
    This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Phthalic_acid". A list of authors is available in Wikipedia.
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