目前,命名旋光异构体的构型国际上普遍采用R/S命名法。但在教学过程中,学生对应用R/S命法标记构型较难掌握。因为一般教科书上所介绍的标记方法,对观察的方向,基团的位置,排列的方向都有一定的要求。而学生由于立体概念模糊,缺乏观察构型式的立体感,尽管对命名原则记得很熟,标记时仍时常出错。本文所给出的标记方法仅从十字形投影式出发就可正确标记记C_abcd~*的构型,较物掌握。关于十字投影式可 At present, the R/S nomenclature is commonly used in the configuration of the named optical isomers. However, in the teaching process, students are more difficult to grasp the application of R / S life mark configuration. Because of the marking methods described in general textbooks, there are certain requirements for the direction of observation, the position of the radicals, and the direction of the alignment. Because of the lack of stereoscopic concept and the lack of three-dimensional perception of the observational structure, students are still familiar with the naming principles and often make mistakes when marking. The marking method given in this article can mark the configuration of C_abcd~* correctly only from the perspective of the cross-projection type, and it can be grasped by the object. About cross projection type