CHEM 213 Chapter Notes - Chapter 15.5-15.6: Sulfonate, Sulfur Trioxide, Sulfuric Acid
20 Mar 2017
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Benzene reacts with fuming sulfuric acid at room temperature: to make benzenesulfonic acid, fuming sulfuric acid = sulfuric acid (h2so4) mixed with sulfur trioxide (so3, sulfonation can also occur in just sulfuric acid, but would take longer. So3 reacts with benzene and makes arenium ion (so3 and an h added onto the benzene, removing a double bond and making a cation: 3. Hso4- comes back and grabs the h off the benzene: 4. H o comes and donates and h to so3-, making so3h and forming benzenesulfonic acid. The overall reaction is reversible for sulfonation: if you want so sulfonate, use concentrated h2so4. Causes sulfonation by pushing equilibrium right: if you want to desulfonate, use diluted sulfuric acid and steam the mixture (adds water) Sulfonate groups can work as protecting groups to prevent substitution. Sulfonate groups can also work as a directing group, to in uence the position of another substitution relative to the position of the so3h.
