Exploration of Factors Affecting the Relative Rate of Electrophilic Aromatic Bromination

The experiments on the relative rates of bromination of different substituted aromatic compounds have been around in organic teaching labs for a long time. One major limitation with these experiments has been the lack of deactivating functional groups. The following experiment represents a new approach, which allows students to investigate the relative rate of not only activating but also deactivating substrates through experiment and deduction, which provides a more thorough view of the substituent effects on electrophilic aromatic substitution (EAS). The first part of the experiment focuses on activating group vs deactivating group, and how both the inductive and resonance effects of the different groups affect the rates. The second part then focuses on the additive effect of the two substituents on the aromatic ring by combining the deactivating and the activating groups from part I. Through logical deduction, the students are then able to determine the overall order of reactivity of all different functional groups.