Regioselectivity of compounds is fundamental in the strategic planning of chemical and biological syntheses. It allows complex molecules to be constructed efficiently or even to be customized for specific applications. Specifically with electrophilic aromatic bromination, aryl bromides serve as useful intermediates for synthesis, as they produce a sigma complex that allows substituents to favor a specific ion to influence the major product produced (Hui-Jing et. al., 2014). This is essential to the production of pharmaceuticals, agrochemicals, and pigments. However, using Br2 is not financially or environmentally friendly, so a bromine reagent is often used.
For this experiment, hypobromous acid is used as the electrophilic bromine reagent, formed using Oxone and KBr. The bromine in KBr is able to attack the alcohol attached to the oxygen that resultsresulting in a hydroxide ion and electrophilic hypobromous acid.

Hypobromous acid was utilized as the electrophilic bromine reagent for the electrophilic bromination of 4-methylanisole. The reaction initiated with the electron-rich ortho position of the pi bond to the methoxy group, as the methoxy group is a strong activator. A strong activating group is aan ortho/para director, but the ortho position to the methoxy was chosen, as it is stronger than the methyl group, which is a weak activator. The pi bond nucleophilically attacks the bromine in hypobromous acid. This results in a cation that rearranges tointo 4 resonance structures within a sigma complex. The resonance structure with the ion at the meta position is favored in this reaction, where the hydroxide ion can deprotonate the hydrogen that is attached to the carbon with bromine. These electrons are able to reform a pi bond that resultresults in the benzene being restored. This produces the desired product 2-bromo-4-methylanisole, which is to be verified through IR spectroscopy and H NMR.