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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.

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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