Alkali, action lactic acid production

The action of alkaline reagents on sugars has been the subject of much study since Lobry de Bruyn s researches in 1896. Many complex changes are induced in the sugar molecule by alkaline reagents, as is exemplified by the researches of Evans.Here, however, mention will be made only of the production of lactic acid by the action of alkali on sucrose. 

Komoto detected lactic acid in the mixture from reaction of D-glucose with ammonia,4 and presumed that it was produced from pyruvaldehyde formed by decomposition of D-glucose. Lactic acid has, indeed, been found as a product of the action of alkali (lime-water) on substituted D-glucose and substituted D-fructose,81,83,96 and the mechanism of its formation involves the reversible aldol reaction, followed by formation of pyruvaldehyde, and the benzilic acid rearrangement already described for saccharinic acid this is illustrated83,96 in Scheme 11. 

The proposed intermediate, 2-0-(/3-D-glucopyranosyl)-D-erythrose (XC), hydrolyzes, supposedly via the enediol, to D-glucose and D-erythrose (XCI). This D-glucose, under the action of alkali, then produces lactic acid. The other products shown above (formaldehyde, glycolaldehyde) are known to be formed by alkaline fragmentation of the carbon chain, and are ordinarily present when alkali acts on a reducing sugar.68... 

Many other suggestions have been made regarding the intermediate steps in the conversion of dextrose into alcohol and carbon-dioxide and the nature of the intermediate products. Buchner and Meisenheimer, B. (1905), 38 620, suggested that lactic acid is the first product of the action of zymase on dextrose since it is known that this acid is formed in muscle tissue by the oxidation of glycogen, which is a polydextrose. They added to this theory the assumption of a second enzyme, lactacidase, which carries on the decomposition of the lactic acid into ethyl alcohol and carbon dioxide cf. Bio. Z. (1922), 128 144 and 132 165. This suggestion was based on the observation that a concentrated solution of dextrose when treated with alkali yields about 3% of alcohol on exposure to sunlight. Under similar conditions a more dilute solution gives a 50% yield of lactic acid. 

In the reaction mixtures of the action of alkali on hexoses, small amounts of methylglyoxal (pyruvic aldehyde) and much lactic acid appear this is proof that the molecule is sensitive to a cleavage of some kind at the center of the chain. These products also occur in the alkali-treated solutions of trioses, along with traces of acetol, lactic aldehyde, and pyruvic acid 74, 93). However, the trioses so rapidly condense to sugars that the appearance of common reaction products does not establish the sequence of reactions. If trioses deliberately are added to an alkaline hexose solution... 

Lactic acid occurs amongst the products of the action of alkali on hexoses. From 1 mole of D-glucose, treated at 25°C. with benzyltrimethylammonium hydroxide, Evans reported the production of 1.2 moles of racemic lactic acid (60 % of a theory of 2 moles per mole hexose). The substance apparently can be obtained by the action of alkali on any sugar (inclusive of trioses, pentoses, disaccharides, etc.) (99). Its preparation from sucrose under conditions of high temperature and pressure has been extensively studied from the viewpoint of potential industrial application. Lactic acid may be considered as the saccharinic acid (see below) related to glyceraldehyde and may arise from the rearrangement of a triose fragment. 

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