RCHOHCOOH

RCHOHCOOH denotes a family of alpha-hydroxy acids (AHAs) with the general structure R-CHOH-COOH. In this motif the carboxyl group is at one end of the carbon chain and a hydroxyl is attached to the adjacent (alpha) carbon. The R group is a variable substituent, so the family includes a range of compounds from glycolic acid (R = H) to more substituted acids such as lactic acid (R = CH3) and mandelic acid (R = C6H5).

AHAs are weak acids. The alpha-hydroxy substitution influences their acidity and reactivity, enabling esterification and lactone formation under appropriate conditions. The alpha carbon is a stereocenter whenever R is not hydrogen and the molecule is not symmetric, so many members exist as enantiomeric pairs (for example, L- and D-lactic acid).

Natural occurrence and production: Many AHAs occur in nature through fermentation and metabolism. Lactic acid arises from dairy fermentation and muscle metabolism, glycolic and other AHAs can be derived from sugars and plant sources. Industrially, AHAs can be produced by oxidation of hydroxyaldehydes or via fermentation routes, and they are commonly manufactured as mixtures or single enantiomers for commercial use.

Applications: AHAs are widely used in cosmetics and dermatology as keratolytic exfoliants and moisturizers. Glycolic acid and lactic acid are common in chemical peels, toners, and creams. In the food and pharmaceutical industries, lactic acid serves as a preservative and flavoring agent, while mandelic and other AHAs find specialized uses in formulations.

Safety: At higher concentrations or low pH, AHAs can cause skin and eye irritation. Products are used under controlled formulations, often with buffering and sun protection to mitigate sensitivity.