The ortho effect arises in certain electrophilic aromatic substitutions when a meta director is
meta to an ortho/para director. Among the three expected isomer products, only the two isomers ortho
to the meta director are produced normally. To find an explanation for the ortho effect, nitrations of
two properly substituted benzenes were explored. Evidence supported an explanation based on resonance
involving the meta director.
Keywords: Electrophilic aromatic substitutions, ortho effect, resonance, nitration, directing groups, meta director.
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