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Isobutyric acid

Isobutyric acid
IUPAC name 2-Methylpropanoic acid
Other names Isobutyric acid
2-Methylpropionic acid
CAS number 79-31-2
Molecular formula C4H8O2
Molar mass 88.10 g/mol
Density 0.9697 g/cm3 at 0 °C
Melting point

-47 °C

Boiling point

155 °C

Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Isobutyric acid, also known as 2-methylpropanoic acid, is a carboxylic acid with structural formula (CH3)2-CH-COOH. It is found in the free state in carobs (Ceratonia siliqua) and in the root of Arnica dulcis, and as an ethyl ester in croton oil.

Additional recommended knowledge

Isobutyric acid is an isomer of n-butyric acid; they have the same chemical formula C4H8 O2 but a different structure.

Isobutyric acid may be artificially prepared by the hydrolysis of isobutyronitrile with alkalis, by the oxidation of isobutanol with potassium dichromate and sulfuric acid,[1] or by the action of sodium amalgam on methacrylic acid. It is a liquid of somewhat unpleasant smell, boiling at 155 °C. Its specific gravity is 0.9697 (0 °C) and pKa is 4.84 (20 °C). Heated with chromic acid solution to 140 °C, it gives carbon dioxide and acetone. Alkaline potassium permanganate oxidizes it to α-hydroxyisobutyric acid, (CH3)2-C(OH)-COOH. Its salts are more soluble in water than those of butyric acid.


  1. ^ I. Pierre and E. Puchot, Ann. de chim. et de phys., 1873, 28, p. 366
  • Merck Index, 11th Edition, 5039.
  • 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 "Isobutyric_acid". A list of authors is available in Wikipedia.
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