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一、费歇尔(Fischer)投影式的由来 有机物的数目特别多,到现在为止,已经超过了七百万种。究其原因,首先是碳原子相互结合的能力强,结合的方式多,其次是有机物中同分异构现象非常普遍。 有机物的同分异构现象可分成两大类:构造异构和立体异构。其中,立体异构又包括顺应异构、对映异构和构象异构三种情况。分子式相同,构造式相同,但构型不同,互为镜象但不能重合的立体异构体叫对映异构体。对映异构体的区别在于它们的构型不同,需要用构型式才能表示出这种区别。例如,乳酸有下列四面体构型:
First, the Fischer projection has a particularly large number of organic matter, and so far it has exceeded seven million. The reason, first of all, the ability of carbon atoms with each other strong combination of many ways, followed by the phenomenon of isomers in organic matter is very common. Isomerism of organic matter can be divided into two broad categories: structural and stereoisomeric. Among them, stereoisomerism also includes three cases of isomerism, enantiomerism andconformational heterogeneity. The same molecular formula, the same structural formula, but the different configurations, but not mirror images of each other but not coincident stereoisomers enantiomers. The difference between enantiomers is that they have different configurations and need to use configuration to represent this difference. For example, lactic acid has the following tetrahedral configuration: