Abstract Cram empirical rules have important applications in judging nucleophilic addition stereoselectivity of carbonyl group having a proximal stereocenter. Newman projection combined with Cram rule is often used to predict main products in current textbooks. Other commonly used conformational expressions such as saw frame, umbrella frame and Fischer projection often require conformational transformation when Cram rules are used. However, this transformation has high requirements on spatial imagination and abstraction, and is prone to errors in learning. It is a difficulty in organic chemistry learning. In this paper, the use of Cram rules is directly discussed through in-depth analysis by using other commonly used conformational expressions, such as saw frame, umbrella frame and Fischer projection, so as to avoid the transformation between conformational expressions that are free of charge, laborious and prone to errors.
XIN Na-Na, GONG Shu-Wen, HUANG Xian-Qiang. Application of Cram Rules in Different Conformational Expressions[J]. Chinese Journal of Chemical Education, 2020, 41(12): 27-30.
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