Nuclear Magnetic Resonance-Based Method to Teach the “Effect of Substituents on the Reactivity and Orientation” of Aromatic Compounds

Abstract

The effect of substituents on the reactivity and orientation is important for aromatic compounds in organic chemistry. The “telling style” is used in traditional teaching methods and does not make a deep impression of the learned content in students. The lack of a clear criterion causes a vague understanding of the orientation of the substituted groups. This study developed a new method termed the “nuclear magnetic resonance (NMR)-based method (NBM)” to teach the “effect of substituents on reactivity and orientation”, which changed the “telling style” teaching method to a “discussing style” teaching method. A normalized method was used to correct the scale of ¹H NMR chemical shift change to that of ¹³C NMR chemical shift change. The sum of the ¹H and ¹³C NMR chemical shift changes was used to discuss the following issues: (i) verifying the activating or deactivating groups, (ii) determining the ortho–para or meta directors, and (iii) predicting the orientation of an incoming group in disubstituted benzene. The NBM presented in this paper is intuitive and simple, which can help students to understand the “effect of substituents on reactivity and orientation” in electrophilic aromatic substitution and cultivate the ability of students to analyze problems using NMR.