CH3CH2CH2COOH

CH3CH2CH2COOH corresponds to butanoic acid, also called butyric acid. It is a saturated carboxylic acid with four carbon atoms in its main chain and a carboxyl group at one end. Its chemical formula is C4H8O2. It is categorized as a short-chain fatty acid.

Physically, butanoic acid is a colorless, oily liquid with a characteristic strong, unpleasant odor often described as rancid butter. It has a boiling point around 164–165°C and a melting point near -5°C. It is moderately soluble in water and soluble in many organic solvents. It behaves as a weak acid, with a dissociation constant (pKa) around 4.8, and it forms salts with bases (butanoates). It readily undergoes esterification with alcohols to give butanoate esters.

Natural occurrence and production: butanoic acid occurs in dairy products as a result of fermentation and lipid breakdown, contributing to rancid flavors and odors. It is produced industrially by chemical routes such as oxidation of n-butanol or by hydrolysis of esters, and it can also be generated biotechnologically through fermentation by certain anaerobic bacteria, notably Clostridium species.

Uses: due to its distinctive odor, butanoic acid is used as a flavor and fragrance ingredient in controlled, small quantities to simulate dairy notes or to create specific aroma profiles. It also serves as an important chemical intermediate in organic synthesis, including the preparation of esters, polymers, and pharmaceutical precursors.

Safety: butanoic acid is corrosive and an irritant to skin, eyes, and mucous membranes. Appropriate handling, ventilation, and personal protective equipment are recommended to minimize exposure.