Lactic acids chemical synthesis

Lactic acid [50-21-5] (2-hydroxypropanoic acid), CH CHOHCOOH, is the most widely occurring hydroxycarboxylic acid and thus is the principal topic of this article. It was first discovered ia 1780 by the Swedish chemist Scheele. Lactic acid is a naturally occurring organic acid that can be produced by fermentation or chemical synthesis. It is present ia many foods both naturally or as a product of in situ microbial fermentation, as ia sauerkraut, yogurt, buttermilk, sourdough breads, and many other fermented foods. Lactic acid is also a principal metaboHc iatermediate ia most living organisms, from anaerobic prokaryotes to humans. 

Other possible chemical synthesis routes for lactic acid include base-cataly2ed degradation of sugars oxidation of propylene glycol reaction of acetaldehyde, carbon monoxide, and water at elevated temperatures and pressures hydrolysis of chloropropionic acid (prepared by chlorination of propionic acid) nitric acid oxidation of propylene etc. None of these routes has led to a technically and economically viable process (6). 

See also PBT degradation structure and properties of, 44-46 synthesis of, 106, 191 Polycaprolactam (PCA), 530, 541 Poly(e-caprolactone) (CAPA, PCL), 28, 42, 86. See also PCL degradation OH-terminated, 98-99 Polycaprolactones, 213 Poly(carbo[dimethyl]silane)s, 450, 451 Polycarbonate glycols, 207 Polycarbonate-polysulfone block copolymer, 360 Polycarbonates, 213 chemical structure of, 5 Polycarbosilanes, 450-456 Poly(chlorocarbosilanes), 454 Polycondensations, 57, 100 Poly(l,4-cyclohexylenedimethylene terephthalate) (PCT), 25 Polydimethyl siloxanes, 4 Poly(dioxanone) (PDO), 27 Poly (4,4 -dipheny lpheny lpho sphine oxide) (PAPO), 347 Polydispersity, 57 Polydispersity index, 444 Poly(D-lactic acid) (PDLA), 41 Poly(DL-lactic acid) (PDLLA), 42 Polyester amides, 18 Polyester-based networks, 58-60 Polyester carbonates, 18 Polyester-ether block copolymers, 20 Polyester-ethers, 26... 

Hydrogen cyanide is an important building block chemical for the synthesis of a variety of industrially important chemicals, such as 2 hydroxy-4 methylthiobutyric acid, adiponitrile, nitrilotriacetic acid, lactic acid, and methyl methacrylate. The primary commercial routes to hydrogen cyanide are the reaction of methane and ammonia under aerobic (Andrussow Process) or anaerobic conditions (Degussa Process), or the separation of hydrogen cyanide as a by-product of the ammoxidation of propylene < ) The ammoxidation of methanol could represent an attractive alternate route to HCN for a number of reasons. First, on a molar basis, the price of methanol has become close to that of methane as world methanol capacity has increased. However, an accurate long term pricing picture for these two raw... 

Fermentation. Fermentation is defined (Ref 3) as the production of chemicals by a series of enzyme catalyzed reactions with bacteria, yeasts, or molds under aerobic or anaerobic conditions. At present, fermentation is used to produce complex molecules not easily synthesized such as penicillin and other antibiotics, vitamin BI2, and enzymes. Formerly, glycerine (See Fetmentol), acetone, butanol, and citric lactic acids were some of the chemicals produced by fermentation process. Synthesis is now a more economical route to these materials (See also Refs 1 2) Refs 1) P.A. Wells G.E. Ward, IEC 31, 172-77(1939) 2) H.E. Silcox S.B. Lee,... 

Various attempts to synthesize biopterin independent of naturally occurring sugars have been carried out (Scheme 11). L-Tartalic acid and (S)-lactic acid were converted to 5-deoxy-L-arabinose (62) and its derivative (67), respectively [76-78]. However, these procedures required multiple steps and cannot be replaced by the procedure using L-rahmnose (65). The stereoselective process of biopterin 7-carboxylic acid (68) starting from E-2-butenoic acid, which is a bulk industrial chemical, looked attractive because the process is thoroughly independent of natural chiral resources, however, it is not applicable to the synthesis of biopterin (30) [79]. 

Most other simple compounds whose history has been examined have been those of obvious industrial interest. Thus, fluorinated compounds have been discussed, especially the now controversial chlorofluorocarbons (CFCs).80 Another aliphatic chemical that has received exhaustive historical treatment, chiefly in the context of its industrial use, is lactic acid.81 The development of urea as a fertilizer has been studied,82 and a history provided of the synthesis of methanol.83... 

Lactic acid, initially produced in 1880, was the first organic acid made industrially by fermentation of a carbohydrate. Nowadays it is made both by fermentation and by chemical synthesis. About 85% of the use of lactic acid is in food and food-related applications, with some use in the making of emulsifying agents and poly(lactic acid). 

There are many organic acids that can be produced by microbial or biochemical means. However, at present, only acetic acid (as vinegar), citric acid, itaconic acid, gluconic acid, 2-keto-gulonic acid, and lactic acid are produced industrially by fermentation. Other organic acids, such as fumaric, gallic, malic, and tartaric acids, once produced by fermentation or enzyme processes, are now produced commercially, predominantly by the more economic means of chemical synthesis. 

Lactic acid is a sour principle of yogurt and lactobacillus beverages. It exhibits a soft and thick sour taste quality with slight astringency. It is a syrupy liquid produced by fermentation with a lactobacillus and is formed in the body by the metabolism of sugars. Due to its pH-controlling effect, it is used in soft drinks, pickles, Japanese sakes, sherbets, and so on. It is industrially produced by the fermentation of glucose and chemical synthesis. Approximately 12 000 tons are consumed annually as a food additive in Japan. 

Grbin et al. 2007). ATHP reduction may lead to EHTP. As ethanol is a precursor, mousy off-flavour occurs after alcoholic fermentation, preferably after lactic acid bacteria activity. It seems that the formation of mousiness may be induced by oxidation but it is not clear if the effect is on the microorganisms or in any chemical reaction stimulated by the redox potential. Other agents claimed to affect its production (high pH, low sulphite, residual sugar content) (Lay 2004 Snowdon et al. 2006 Romano et al. 2007) are also stimulators of microbial activity and so the true mechanisms are not yet clarified, but the non-enzymatic chemical synthesis has been ruled out in D. anomala (Grbin et al. 2007). 

Lactic acid is a major end product from fermentation of a carbohydrate by lactic acid bacteria (Tormo and Izco, 2004). However, lactic acid can be produced commercially by either chemical synthesis or fermentation. The chemical synthesis results in a racemic mixture of the two isomers whereas during fermentation an optically pure form of lactic acid is produced. However, this may depend on the microorganisms, fermentation substrates, and fermentation conditions. Lactic acid can be produced from renewable materials by various species of the fungus Rhizopus. This has many advantages as opposed to bacterial production because of amylolytic characteristics, low nutrient requirements, and the fungal biomass, which is a valuable fermentation by-product (Zhan, Jin, and Kelly, 2007). 

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