StructureΒ
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- Formula: The molecular formula for butyric acid is
C4H8O2cap C sub 4 cap H sub 8 cap O sub 2πΆ4π»8π2
- Systematic name: The IUPAC (International Union of Pure and Applied Chemistry) name is butanoic acid.
- Structure: Butyric acid consists of a four-carbon chain with a carboxyl (
COOHcap C cap O cap O cap HπΆπππ»Β functional group at one end. The structure can be written asCH3(CH2)2COOHcap C cap H sub 3 open paren cap C cap H sub 2 close paren sub 2 cap C cap O cap O cap HπΆπ»3(πΆπ»2)2πΆπππ»
- Formula: The molecular formula for butyric acid is
Chemical and physical propertiesΒ
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- Appearance: It is a colorless, oily liquid.
- Odor: It has a strong, unpleasant smell similar to rancid butter.
- Taste: It has a somewhat butter-like taste with a sweet aftertaste.
- Molar mass: 88.11 g/mol.
- Solubility: Miscible with water, ethanol, and ether.
- Density: 0.960 g/mL at 20 Β°C.
- Melting point:-5.1negative 5.1β5.1Β°C (22.8 Β°F).
- Boiling point: 163.75 Β°C (326.75 Β°F).
- Weak acid: Butyric acid has a pKa of 4.82, which means it is a weak acid that readily reacts with bases to form salts and esters called butyrates or butanoates.Β
OccurrenceΒ
Butyric acid occurs naturally in various sources:Β
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- Dairy products: It is found as a glyceride in milk, especially goat, sheep, and buffalo milk, and makes up about 3β4% of butter.
- Rancid butter: When butter becomes rancid, butyric acid is liberated by the hydrolysis of its glycerides, producing its characteristic foul odor.
- Mammalian gut: It is produced in the colon through the anaerobic fermentation of dietary fiber by gut bacteria. This makes it a crucial energy source for the cells lining the colon.
- Other natural sources: It is also found in parmesan cheese, vomit, body odor, and plant and animal fats.Β
ProductionΒ
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- Industrial production: Butyric acid is commercially produced via the hydroformylation of propene and syngas to form butyraldehyde, which is then oxidized to create butyric acid.
- Microbial biosynthesis: It can also be produced through the fermentation of sugars or starches by specific anaerobic bacteria, such as Clostridium species. This process was discovered by Louis Pasteur in 1861.Β
UsesΒ
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- Food and flavoring: Esters of butyric acid, such as methyl and ethyl butyrate, have mostly pleasant, fruity aromas and are used as food additives and flavorings.
- Plastics: It is used in the synthesis of cellulose acetate butyrate (CAB), a thermoplastic with increased flexibility and resistance to degradation compared to cellulose acetate.
- Health and medicine: As a short-chain fatty acid, butyrate provides a major energy source for colon cells, helps maintain a healthy gut, and has anti-inflammatory properties. It has been studied for potential therapeutic benefits for gastrointestinal disorders and colorectal cancer.
- Fishing bait: Due to its powerful odor, it is used as an additive in fishing bait.
- Perfumes and fragrances: Esters of butyric acid are used as aromatic compounds in the perfume industry.Β
Safety and handlingΒ
Butyric acid is a combustible and corrosive liquid. Direct contact can cause severe skin and eye burns, and inhalation may irritate the respiratory tract. Standard personal protective equipment should be used during handling.







