Abstract

Electrophilic Aromatic Substitution (EAS) reactions are very important reactions of benzene rings, which are extremely common groups in organic molecules. An interesting characteristic of some EAS reactions is called the ortho effect and has never been adequately explained. The ortho effect arises when a substituted benzene compound with a resonance-capable meta-director that is meta to an ortho/para-director is subjected to an EAS reaction, which results in an abnormal product distribution in that only two of the three predicted products form. An example of this can be seen in the nitration of 3-nitrochlorobenzene. We have hypothesized that this distribution is the result of increased resonance possibilities with the meta-director in the reaction intermediate. If the ortho effect is indeed due to resonance, using a meta-director that is not resonance-capable, such as a trifluoromethyl group, would restore the expected product distribution. In this study, 3-chlorobenzotrifluoride was subjected to an EAS nitration reaction. The products of this reaction were analyzed by ¹H NMR, ¹³C NMR, and HSQC NMR experiments. The NMR data indicates that the product that was suppressed by the ortho effect in the EAS reaction with 3-nitrochlorobenzene was present in the products of the EAS reaction with 3-chlorobenzotrifluoride, providing strong evidence that the ortho effect is due to resonance.