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Isobutyric acid

Isobutyric acid

IUPAC name	2-Methylpropanoic acid
Other names	Isobutyric acid 2-Methylpropionic acid
Identifiers
CAS number	79-31-2
SMILES	CC(C)C(=O)O
Properties
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 (C H₃)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.

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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.

References

^ 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.

Category: Carboxylic acids