Blocking Groups - Sulfonic Acid - Online Tutor, Practice Problems & Exam Prep

Unlike other electrophilic aromatic substitutions, benzene sulfonation is reversible. Sulfonic acid can be added to the benzene ring and removed later. This makes the sulfonic acid group alternatively known as the "blocking group." Show how to synthesize 1,2,3-tribromobenzene starting from benzene, using sulfonation and de-sulfonation as intermediate steps.