What Is Butyric Acid?
Butyric acid, also known as orthobutyric acid, is a four-carbon aliphatic carboxylic acid. It is an oily, colorless liquid with an unpleasant odor reminiscent of rancid butter. Even in minimal quantities, mammals can detect its scent. It has a structural isomer known as isobutyric acid.
Butyric acid occurs naturally in animal milk fat as glycerides and in plant essential oils as esters. It is also produced through the fermentation of sugars and lactic acid and can be synthesized industrially by the oxidation of butyraldehyde and butanol.
Uses of Butyric Acid
Butyric acid serves various functions, including as a raw material for varnish production, organic synthesis (e.g., 4-heptanone), and emulsifiers. It’s a precursor for biofuel production and, when esterified, is used in synthetic fragrance manufacturing. Additionally, it finds applications in food processing, flavor enhancers, animal feed to boost nutrition and prevent diseases, and pharmaceuticals for treating cancer and irritable bowel syndrome.
Properties of Butyric Acid
With a density of 0.96 g/cm3 and a molecular weight of 88.11, butyric acid has a melting point of -7.9°C and a boiling point of 164°C. It is miscible with water, ethanol, and ether, and insoluble in brine, allowing for separation by salt addition. As a weak acid, its pKa is 4.82, making it slightly more acidic than acetic acid (pKa = 4.76).
Its chemical structure is CH3(CH2)2COOH, and it is sometimes referred to as butanoic acid or n-butanoic acid.
Other Information on Butyric Acid
1. Butyric Acid in Nature
Derived from butter (Latin butyrum), butyric acid is biosynthesized during fatty acid breakdown and is widely present in nature. It contributes to the distinctive odors of body secretions, such as sebum and sweaty feet, and is found in cheese, butter, and certain plants like ginkgo biloba.
2. Butyric Acid as a Source of Energy
In herbivores, butyric acid is a vital energy source, produced by the anaerobic fermentation of cellulose and hemicellulose in the digestive system. It undergoes beta-oxidation to form acetyl-CoA, fueling the citric acid cycle. In the colon, it serves as a preferred energy source for colon cells and has anti-inflammatory properties, aiding intestinal repair.
3. Structural Isomers of Butyric Acid
Isobutyric acid, or 2-methylpropionic acid, is a structural isomer of butyric acid, with the formula (CH3)2CHCOOH. It occurs naturally, sometimes in esterified form in certain plants.
4. Related Compounds of Butyric Acid
Propionic acid (CH3CH2COOH) and pentanoic acid (CH3(CH2)3COOH), also known as yoshinoic acid, are related saturated fatty acids, containing three and five carbon atoms, respectively.