Lactic acid; DL-ALPHA-HYDROXYPROPIONIC ACID

Lactic acid is an important organic acid, second only to citric acid in terms of production and consumption. Data shows that lactic acid consumption accounts for about 15% of total organic acid consumption. In recent years, due to the expanded application of L-lactic acid in biodegradable plastics, its demand is expected to grow rapidly, and some predict that it may catch up with or surpass citric acid in a few years. Lactic acid is widely found in nature and has been found in all living organisms. Also known as 2-hydroxypropionic acid or α-hydroxypropionic acid, its molecular structure contains one asymmetric carbon atom, forming two optical isomers: the d-isomer and the l-isomer, and the racemic dl-isomer, for a total of three optical isomers. It was named lactic acid after Scheele, who discovered it in yogurt in 1780. In human and animal meat tissue, the dextrorotatory and racemic isomers exist, while the levorotatory isomer is a normal metabolite in mammals. It is also naturally found in poppies, apples, tomato juice, and other fruits. Commercially available products, whether obtained through fermentation or synthesis, are all racemic chemical book compounds. Due to the presence of hydroxyl and carboxyl groups in the molecule, this product exhibits the functions of both functional groups. It reacts with acid anhydrides to form carboxylic acid esters, with alcohols to form lactic acid esters, and with sodium, calcium, and ferrous ions to form salts. Because it possesses both hydroxyl and carboxyl groups, it can undergo auto-esterification to form linear polyesters, and even cyclic compounds, namely cyclic dimers such as lactide. Under slow oxidation conditions, it can produce pyruvate; heating above 250°C causes chain scission and decomposition to produce acetaldehyde, releasing carbon dioxide and water. It can react with ammonia or amines to form lactamides. Besides auto-esterification, the hydroxyl and carboxyl groups can also participate in reactions simultaneously, such as reacting with aldehydes or ketones to form cyclic acetals. Sodium lactate is used in medicine to prevent acidosis. Ferric lactate and calcium lactate are raw materials in the pharmaceutical industry. Ethyl lactate is a fragrance, and butyl lactate is a good additive for paints. It is also an important raw material for plasticizers and modifiers in the plastics industry. In the electroplating industry, it is used as a rust remover.