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Benzene and Its Derivatives - How Do Existing Substituents on Benzene Affect Electrophilic Aromatic Substitution?

4 important questions on Benzene and Its Derivatives - How Do Existing Substituents on Benzene Affect Electrophilic Aromatic Substitution?

What effect can substituents have on the further eletrophilic aromatic substitution of benzene?

1. Substituents can affect the orientation of the new group.
2. Substituents can affect the rate of substitution of the new group.

What is an ortho-para director?

Any substituent on a benzene that directs electrophilic substitution to ortho and para positions.

What generalizations about substituent groups to benzene can be made?

1. Any substituent containing an atom with an unshared electron pair next to the benzene ring is ortho-para directing. The rest is meta directing.
2. All ortho-para directing substituents are activating, except for halogens.
3. All meta directing groups carry a full or partial positive charge on the atom directly bonded to the benzene ring.

Why are halogens deactivating?

1. Halogens are more electronegative and will induce the reactivity of the benzene ring.
2. A halogen can stabilize the cation by delocalizing its positive charge.