hydroxycarboxylic

Hydroxycarboxylic acids are organic compounds that contain both a carboxyl group (-COOH) and one or more hydroxyl groups (-OH) within the same molecule. They are found in nature, arise in metabolism, and are produced in industry for various applications. A common way to classify them is by the position of the hydroxyl group relative to the carboxyl group. Alpha-hydroxy acids (AHAs) have the hydroxyl on the carbon immediately adjacent to the carboxyl carbon, with examples such as glycolic acid (2-hydroxyacetic acid) and lactic acid (2-hydroxypropanoic acid). Beta-hydroxy acids (BHAs) have the hydroxyl on the beta carbon, such as 3-hydroxypropionic acid. More complex polyhydroxycarboxylic acids include citric and malic acids, which carry multiple carboxyl and hydroxyl groups.

Natural occurrence and production vary: hydroxycarboxylic acids appear in fruits, dairy products, and plant tissues, and they arise in metabolic pathways such as glycolysis. Industrially, they can be produced by fermentation or by chemical oxidation of carbohydrates, and they serve as important chemical intermediates. Lactic and glycolic acids are notable for cosmetic and polymer applications; lactic acid is used in foods and, together with glycolic acid, as a feedstock for biodegradable polymers like polylactic acid.

Key properties include acidity from the carboxyl group, the ability to form strong hydrogen bonds, and solubility that depends on the number and position of hydroxyl groups. Safety and regulatory considerations emphasize that concentrated solutions can irritate skin or eyes, but many hydroxycarboxylic acids are biodegradable and used under appropriate guidelines.