Substitution into benzene rings {benzene ring reaction} replaces a hydrogen on a ring carbon with nitro, sulfoxy, halogen, or other nucleophilic substituent.
process
Strong acid, such as iron (III) chloride or aluminum chloride, can slowly polarize benzene-ring carbon atom to make carbocation. Carbocation resonates at attacked-carbon ortho carbon and para carbon. Nucleophile quickly adds to attacked carbon, and hydrogen ion leaves.
process: already substituted
If benzene ring already has one nitro, sulfoxyl, halogen, or other nucleophilic substituent, substituted nucleophile substituent has positive charge.
If benzene ring already has one nitro, sulfoxyl, halogen, or other nucleophilic substituent, electron-donating nucleophilic substituent quickly adds to substituted-carbon ortho carbon or para carbon.
If benzene ring already has one nitro, sulfoxyl, halogen, or other nucleophilic substituent, and bromine or strong acid polarizes carbon atom to make carbocation, electron-withdrawing nucleophile can slowly add to substituted-carbon meta carbon.
resonances
Meta carbon and substituted carbon have three resonance structures. Substituted carbon and ortho or para carbons have four resonance structures.
Physical Sciences>Chemistry>Organic>Chemical Reaction
5-Chemistry-Organic-Chemical Reaction
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Date Modified: 2022.0224