厦门大学化学化工学院：《有机化学》课程教学资源（课件讲稿，双语版）第三章 立体化学 Sterochemistry 3.1 旋光性和分子结构的对称因素 3.2.1含一个手性碳原子的化合物

Before 1951 only relative configurations of chiral molecules were known. Configurations of chiral molecules were related to each other through reactions of known stereochemistry. The standard compound was glyceraldehyde

An equimolar mixture of two enantiomers is called a racemic form (either a racemate or a racemic mixture). A racemic form shows no rotation of plane￾polarized light

Isomers are different compounds that have the same molecular formula. Constitutional isomers are isomers that differ because their atoms are connected in a different order. Stereoisomers differ only in arrangement of their atoms in space.Stereoisomers are not constitutional isomers. Enantiomers are stereoisomers whose molecules are nonsuperposable mirror images of each other. Diastereomer are stereoisomers whose molecules are not mirror images of each other

氨基酸是生物体合成蛋白质的原料，同时也是高等动物中许多重要生物分子的前体。例如：激素、 嘌呤、嘧啶、卟啉和某些维生素等。不同机体利用氮源合成氨基酸的能力大不相同。脊椎动物不能合成 全部氨基酸。高等动物能利用铵离子作为合成氨基酸的氮源，但不能利用亚硝酸、硝酸和大气氮

First order overall (一级反应) The reaction is a unimolecular nucleophilic substitution（单分子亲核取代反应）