In 1808, Marus discovered polarized light 。 Since then, French physicist Biot, French crystallographer Wu Yu and chemists have discovered many inorganic crystals and some Organic matter With Plane polarized light The ability of the vibration plane to rotate. But they failed to explore this Optical rotation The reason for the difference. Louis Pasteur (1822-1895) was Biot's assistant in 1848, Paris Normal University Of young teachers have just graduated from Besanson Royal College (with a doctorate in science). In order to make him have Crystallography For some experience in research, his tutor asked him to make a research report on tartaric acid and Racemic tartaric acid The crystal form of the working mirror was investigated again. In his work, Buss affirmed Prouostag's observation, and noted that the crystal of externally consumed ammonium sodium tartrate is composed of two crystals with different planar properties. Their crystal form relationship is like the relationship between left and right hands. When these two kinds of equal weight crystals are mixed together, their mixed solution does not show optical rotation 。 Because of this Optical rotation Pasteur infers that this is not a crystal property but a molecular property. He proposed that the molecules constituting the crystal are mirror images of each other, just like the two crystals themselves. He proposed that there are Isomer That is, the difference in structure only lies in mutual mirror image, and the difference in nature only lies in rotation polarized light In different directions. So Prouostage was the first to find Racemic tartaric acid Of optical activity The reason is that it is a mixture of "left-handed" and "right-handed" tartaric acid, and he found the enantiomeric phenomenon in externally eliminated tartaric acid crystals. In 1874, Van Hoff proposed carbon atom Of tetrahedron He proposed that if there are four different carbon atoms Group These four groups can have two different arrangements around the carbon atom, and two different tetrahedral space configurations. They are mirror images of each other, just like the relationship between people's left and right hands. They are similar in shape but cannot overlap. [1] 
Enantiomer 1. Two stereoisomers that mirror each other but cannot coincide are called enantiomers, or simply enantiomers.
2. Enantiomers refer to compounds with the same molecular formula, which are caused by the different spatial configurations of atoms Isomerism 。 3. Mutual Optical isomer Because the substituent of one of the asymmetric carbon atoms has different orientation in space, they form the relationship between object and mirror image, and they cannot overlap in space. They are called enantiomers. [1] The enantiomers have the same physical properties (such as melting point, boiling point, solubility, refractive index, acidity, density, etc.), thermodynamic properties (such as free energy ， enthalpy , entropy, etc.) and chemical properties. Unless in a chiral environment (such as chiral reagents, Chiral solvent ）Only in the middle show differences. Enantiomeric pair polarized light Their functions are different Specific rotation The values are the same, but the direction is opposite. Enantiomeric organism activity Different, the chemical reaction shows equal rate. Equivalently Levorotator And Dextral body Mixture composition of Racemate 。 [2] Separate a single optical from the enantiomer Isomer The method of disassembly is called disassembly. The most common method of disassembly is to Racemate Generated by the action of ions (called disassembling agents) opposite to optical activity Diastereomer 。 
tartaric acid lactic acid There are three different sources: one is lactic acid extracted from animal muscle, which is dextral; The other is lactic acid obtained by fermentation, which is a left-handed body; The third one is synthetic, which is racemate. There is an asymmetric carbon atom in the molecule, which has optical activity, so there is L-lactic acid and D-lactic acid Two optical isomers. 
