Lactic acid Dextro

In general, the maximum number of optically active isomers is given by 2n where n represents the number of asymmetric carbon atoms. Thus for a compound where n = 1, as in lactic acid, there would be two stereoisomers, one the dextro and the other the laevo. For a compound with two asymmetric carbon atoms, there would be 22 = 4 stereoisomers. But if the two asymmetric carbon atoms carry exactly identical groups, as in tartaric acid, the number would be fewer than four and we know that it exists in three forms, the d the 1 and the meso. 

Dextro Lactic Acid or Sarco-lacUc Acid.— Dextro lactic acid is found in muscular tissue and on this account it is known as sarco-lactic acid. It is also known as para-lactic acid. It was discovered by Liebig... 

Levo Lactic Acid.— Levo lactic acid was first obtained by the fermentation of cane sugar by specific bacteria. It is levo rotatory but, like the dextro acid, the rotation of its salts and its anhydride is reversed, being dextro rotatory. The levo lactic acid and also the dextro acid may be obtained by splitting the inactive acid into its optical components by means of its strychnine salt. 

One of the above formulas may be taken to represent the dextro form and the other the levo. The mixture of the two will produce the inactive acid. Now these three forms of tartaric acid are all known and they bear to each other exactly the same relation as has been explained in connection with lactic acid. The inactive form is able to be split into its two optical components like the inactive lactic acid. These three acids are as follows,... 

It is this fourth unresolvable inactive tartaric acid which gives to tartaric acid its especial interest and importance in connection with the theory of stereo-isomerism. This acid, like the other three, has been fully explained in accordance with the tetra-hedral theory of van t Hoff and LeBel. The explanation rests upon the fact that there is a second asymmetric carbon atom in tartaric acid. We may construct, by models, or, by drawings, space-formulas for tartaric acid. According to the tetra-hedral theory, the dextro, levo and racemic inactive forms will be as follows, analogous to the corresponding formulas for the three lactic acids. The meso-tartaric acid is represented by the third drawing. 

Inactive lactic acid results when lactic acid is prepared by the synthetic methods which have been mentioned (294). The inactive acid may be separated into its constituents by the use of certain general methods which have been found applicable in such cases. While the salts of the dextro and levo forms of active acids with a metallic element have the same solubility, and can not, therefore, be separated by crystallization, the salts formed from these acids and certain organic bases which are optically active differ in solubility. By the fractional crystallization of the strychnine salt of inactive lactic acid, two salts can be separated. The acids obtained from these differ in their action on polarized light one is dextro-rotatory, and the other levo-rotatory. 

An active form of an acid may be obtained from the inactive variety by subjecting it to the action of certain bacteria, which destroy one form of the acid more rapidly than the other. In the case of lactic acid the dextro form may be obtained by the action of the mould called penicillium glaucum on inactive ammonium lactate. When lactic acid is made by the fermenta-... 

F. Beilstein/ by the action of silver oxide on j8-iodopropionic acid obtained what he called hydracrylic acid, since it decomposed on heating into water and acrylic acid, and he formulated it C12H22O11. Its correct formula was found by W. Moldenhauer.2 Heintz believed that it was the same as Wislicenus s ethylene lactic acid, giving a zinc-calcium double salt, but Wislicenus thought they were different. The position was first clarified by Erlenmeyer, who showed that Wislicenus s ethylene lactic acid is hydracrylic acid. Wisli-cenus had found that paralactic acid is optically active (dextro-rotatory), whilst ordinary fermentation lactic acid is inactive, and he supposed that they should be represented by the same formula, CH3 CH(0H)-C02H. He says (1869) Thus is given the first certainly proved case in which the number of isomers exceeds the number of possible structures. Facts like these compel us to explain diflFerent isomeric molecules with the same structural formula by different positions of their atoms in space, and to seek for definite representations of these. ... 

Enantiomer i- nan-te-o-mor [Gk enangtios + E -mer] (ca. 1929) n. Either of a pair of chemical compounds whose molecular structures have a mirror-image relationship to each other. An asymmetric molecule that is the mirror image of its stereoisomer. The two isomers are given the prefixes dextro-and leva-, e.g., d- and Mactic acid. The physical properties of pure enantiomers are equal within experimental error, yet mixtures of the two, called racemic mixtures, may have different properties. For example, 50-50 d/ -lactic acid melts 20°C lower than its pure enantiomers. 

The two lactic acid isomers shown in Figure 10.15 are labeled o-lactic acid and L-lactic acid (d is for dextro, meaning right l is for levo, meaning left). They might be expected to have quite similar properties, and they do. They have identical melting points, boiling points, and solubilities, for instance. And if we try to prepare lactic add in the... 

Lactic acid exists as two position isomers, primary or /S-Iactic acid CH2OH.CH2.COOH, and secondary or a-lactic acid CH3.CHOH.COOH. This last form possesses an asymmetric carbon atom and therefore exists as a laevo- and a dextro- rotatory form. 

Palade et al, 2001). The stereo-isomeric l/d ratio of the lactate unit association influenced PLA properties (Tsuji and Ikata, 1992). There are three types of PLAs because there are two stereoisomeric forms of lactic acid, poly (levo-lactic acid) and poly (dextro-lactic acid), which are both semi-crystalline and have identical chemical and physical properties. Poly (D,L-lactic acid) or poly (meso-lactic acid), a racemic polymer obtained from an equimolar mixture of D- and L- lactic acid, is amorphous, with weak mechanical properties. The... 

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