How is SO3H added to a benzene ring with two substituents present

If a benzene ring with an isopropyl group in the first position and bromine in the 3rd position was mixed with SO3 and H2SO4, where would the SO3H attach? Since Br is a deactivating agent that directs ortho/para and isopropyl is a weak activating agent that's also an ortho/para director, would it be in between the two groups in position 2 or in position 4?




In an EAS reaction the strongest activator will control the directing effects. This means that on a benzene ring that contains an isopropyl group and a bromine you can expect the isopropyl group to control the directing effects. In the sulfonation reaction that you are describing you must also take into account steric effects of the isopropyl group. Because the isopropyl group is rather bulky the group being added will add para in regards to the isopropyl group. This is also convenient because if the group is added para to the isopropyl group it will also be ortho the bromine.


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