Lactic acid is an organic acid. It has a molecular formula CH3CH(OH)COOH. It is white in solid state and it is miscible with water.[2] While in liquid state (dissolved state) it is a colorless solution. Production includes both artificial synthesis as well as natural sources. Lactic acid is an alpha-hydroxy acid (AHA) due to the presence of a hydroxyl group adjacent to the carboxyl group. It is used as a synthetic intermediate in many organic synthesis industries and in various biochemical industries. The conjugate base of lactic acid is called lactate. In solution, it can ionize a proton from the carboxyl group, producing the lactate ion CH3CH(OH)CO−
2. Compared to acetic acid, its pKa is 1 unit less, meaning lactic acid is ten times more acidic than acetic acid. This higher acidity is the consequence of the intramolecular hydrogen bonding between the α-hydroxyl and the carboxylate group. Lactic acid is chiral, consisting of two enantiomers. One is known as l-(+)-lactic acid or (S)-lactic acid and the other, its mirror image, is d-(−)-lactic acid or (R)-lactic acid. A mixture of the two in equal amounts is called dl-lactic acid, or racemic lactic acid. Lactic acid is hygroscopic. dl-Lactic acid is miscible with water and with ethanol above its melting point, which is around 16, 17 or 18 °C. d-Lactic acid and l-lactic acid have a higher melting point. Lactic acid produced by
fermentation of
milk is often racemic, although certain
species of bacteria produce solely
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