Karboksyylin

Karboksyylin is a term that appears in some non-English sources as a designation for the carboxyl functional group in organic chemistry. It is not widely used in major English-language chemical nomenclature; in standard terminology the group is referred to as the carboxyl group, a part of carboxylic acids.

The carboxyl group has the structural formula -COOH, consisting of a carbonyl carbon double-bonded to an oxygen and single-bonded to a hydroxyl group. Through resonance, the group is able to delocalize electrons, which contributes to its acidic character. In solution, carboxyl groups typically lose a proton to form carboxylate anions (-COO−), with pKa values around 4–5 for simple aliphatic acids, and higher or lower depending on substituents and environment.

Reactivity: Carboxyl groups participate in a variety of condensation and substitution reactions. They readily undergo esterification with alcohols to form esters, and amidation with amines to produce amides. They can form anhydrides from carboxylic acids and may decarboxylate under strong heating or catalytic conditions. Salts of carboxylates are common and influence solubility and reactivity in aqueous and organic media.

Occurrence and significance: Carboxyl groups are ubiquitous in biology and industry, found in fatty acids, amino acids, many vitamins and pharmaceuticals, and in numerous polymers. They play a central role in metabolism, catalysis, and materials chemistry, where their acidity and reactivity govern many processes.

Nomenclature and usage: In IUPAC naming, the carboxyl group is often referred to as the carboxyl group; derivatives are named as carboxylic acids, such as ethanoic acid. The term karboksyylin is not standard in English, with most references using “carboxyl” or “carboxyl group.”