EAS Series: Video 5
Aromatic Sulfonation is an Electrophilic Aromatic Substitution (EAS) reaction which adds an SO3H to the benzene ring.
This reaction can be carried out starting with SO3, or creating SO3 using a heated H2SO4 solution. The video below shows the complete mechanism from creating a super electrophile (SO3) to sigma complex and reforming the benzene ring.
(Watch on YouTube: Sulfonation. Click CC on bottom right for transcript.)