Chapter 4.4, Problem 4.29P

And now, for a challenging problem, try to draw the mechanism of a desulfonation reaction (a reaction where we take the SO₃H group off of the ring). The process will be exactly the reverse of what you just drew in the previous problem. There will be three steps: (1) remove the proton from the SO₃H group, (2) H⁺ comes on the ring, and then (3) SO₃ comes off of the ring. The truth is that there are only two core steps here: H⁺ comes on the ring, and then SO₃ comes off of the ring. You can actually pull the proton off of the SO₃H group at the same time that SO₃ comes off of the ring. Try to do it yourself, and if you get stuck, you can look at the answer in the back of the book. Make sure that your mechanism involves an intermediate sigma complex (with a resonance-stabilized positive charge).