carboxylicacid

Carboxylic acids are a family of organic compounds that contain the carboxyl functional group, -COOH, typically written as R-COOH. The carboxyl group consists of a carbonyl (C=O) bonded to a hydroxyl group (–OH) on the same carbon, giving the molecule both an acidic and a carbonyl character.

Most carboxylic acids are weak acids. In water they donate a proton from the carboxyl group to form a carboxylate anion (R-COO−) and hydronium. The common aliphatic carboxylic acids have pKa values around 4–5, though substituents and conjugation can alter acidity. They form hydrogen-bonded dimers in the solid state and in nonpolar solvents, which contributes to relatively high boiling points. Smaller carboxylic acids are generally miscible with water, while solubility decreases as the hydrocarbon substituent grows.

Examples include formic acid (HCOOH), acetic acid (CH3COOH), propionic acid (C2H5COOH), and benzoic acid (C6H5COOH). Carboxylic acids occur in nature and are produced industrially by oxidation of aldehydes or primary alcohols, through fermentation, or by oxidation of hydrocarbons. They have wide use, with acetic acid as a component of vinegar, and benzoic acid and related acids used as preservatives and flavoring agents.

Reactivity and derivatives are central to carboxylic acid chemistry. They readily undergo esterification with alcohols to form esters, typically with an acid catalyst. They react with bases to form carboxylate salts. They can be converted to acid chlorides and anhydrides, or reduced to primary alcohols. Decarboxylation can occur by heating, especially for certain substituted acids.

Applications span polymers (polyesters, polyacrylates), solvents, food additives, and pharmaceuticals, reflecting the versatility of the carboxyl functional group.